CHAPTER XII

KEYS TO THE ARTHROPODS NOXIOUS TO MAN 257-317

Crustacea.

Myriapoda, or centipedes and millipedes.

Arachnida (Orders of).

Acarina or ticks.

Hexapoda (Insecta).

Siphunculata and Hemiptera (lice and true bugs).

Diptera (mosquitoes, midges, and flies).

Siphonaptera (fleas).

APPENDIX

Hydrocyanic acid gas against household insects 318-320

Proportion of ingredients. A single room as an example.

Fumigating a large house. Precautions.

Lesions produced by the bite of the black-fly 321-326

BIBLIOGRAPHY 327-340

INDEX 341-348

CHAPTER I.

INTRODUCTION

EARLY SUGGESTIONS REGARDING THE TRANSMISSION OF DISEASE BY INSECTS

Until very recent years insects and their allies have been considered as

of economic importance merely in so far as they are an annoyance or

direct menace to man, or his flocks and herds, or are injurious to his

crops. It is only within the past fifteen years that there has sprung

into prominence the knowledge that in another and much more insiduous

manner, they may be the enemy of mankind, that they may be among the

most important of the disseminators of disease. In this brief period,

such knowledge has completely revolutionized our methods of control of

certain diseases, and has become an important weapon in the fight for

the conservation of health.

It is nowhere truer than in the case under consideration that however

abrupt may be their coming into prominence, great movements and great

discoveries do not arise suddenly. Centuries ago there was suggested the

possibility that insects were concerned with the spread of disease, and

from time to time there have appeared keen suggestions and logical

hypotheses along this line, that lead us to marvel that the

establishment of the truths should have been so long delayed.

One of the earliest of these references is by the Italian physician,

Mercurialis, who lived from 1530 to 1607, during a period when Europe

was being ravaged by the dread "black death", or plague. Concerning its

transmission he wrote: "There can be no doubt that flies feed on the

internal secretions of the diseased and dying, then, flying away, they

deposit their excretions on the food in neighboring dwellings, and

persons who eat of it are thus infected."

It would be difficult to formulate more clearly this aspect of the facts

as we know them to-day, though it must always be borne in mind that we

are prone to interpret such statements in the light of present-day

knowledge. Mercurialis had no conception of the animate nature of

contagion, and his statement was little more than a lucky guess.

Much more worthy of consideration is the approval which was given to his

view by the German Jesuit, Athanasius Kircher in 1658. One cannot read

carefully his works without believing that long before Leeuwenhook's

discovery, Kircher had seen the larger species of bacteria. Moreover, he

attributed the production of disease to these organisms and formulated,

vaguely, to be sure, a theory of the animate nature of contagion. It has

taken two and a half centuries to accumulate the facts to prove his

hypothesis.

The theory of Mercurialis was not wholly lost sight of, for in the

medical literature of the eighteenth century there are scattered

references to flies as carriers of disease. Such a view seems even to

have been more or less popularly accepted, in some cases. Gudger (1910),

has pointed out that, as far back as 1769, Edward Bancroft, in "An Essay

on the Natural History of Guiana in South America," wrote concerning the

contagious skin-disease known as "Yaws": "It is usually believed that

this disorder is communicated by the flies who have been feasting on a

diseased object, to those persons who have sores, or scratches, which

are uncovered; and from many observations, I think this is not

improbable, as none ever receive this disorder whose skins are whole."

Approaching more closely the present epoch, we find that in 1848, Dr.

Josiah Nott, of Mobile, Alabama, published a remarkable article on the

cause of yellow fever, in which he presented "reasons for supposing its

specific cause to exist in some form of insect life." As a matter of

fact, the bearing of Nott's work on present day ideas of the insect

transmission of disease has been very curiously overrated. The common

interpretation of his theory has been deduced from a few isolated

sentences, but his argument appears quite differently when the entire

article is studied. It must be remembered that he wrote at a period

before the epoch-making discoveries of Pasteur and before the

recognition of micro-organisms as factors in the cause of disease. His

article is a masterly refutation of the theory of "malarial" origin of

"all the fevers of hot climates," but he uses the term "insect" as

applicable to the lower forms of life, and specific references to

"mosquitoes," "aphids," "cotton-worms," and others, are merely in the

way of similes.

But, while Nott's ideas regarding the relation of insects to yellow

fever were vague and indefinite, it was almost contemporaneously that

the French physician, Louis Daniel Beauperthuy argued in the most

explicit possible manner, that yellow fever and various others are

transmitted by mosquitoes. In the light of the data which were available

when he wrote, in 1853, it is not surprising that he erred by thinking

that the source of the virus was decomposing matter which the mosquito

took up and accidentally inoculated into man. Beauperthuy not only

discussed the role of mosquitoes in the transmission of disease, but he

taught, less clearly, that house-flies scatter pathogenic organisms. It

seems that Boyce (1909) who quotes extensively from this pioneer work,

does not go too far when he says "It is Dr. Beauperthuy whom we must

regard as the father of the doctrine of insect-borne disease."

In this connection, mention must be made of the scholarly article by the

American physician, A. F. A. King who, in 1883, brought together an all

but conclusive mass of argument in support of his belief that malaria

was caused by mosquitoes. At about the same time, Finley, of Havana, was

forcefully presenting his view that the mosquito played the chief role

in the spread of yellow fever.

To enter more fully into the general historical discussion is beyond the

scope of this book. We shall have occasion to make more explicit

references in considering various insect-borne diseases. Enough has been

said here to emphasize that the recognition of insects as factors in the

spread of disease was long presaged, and that there were not wanting

keen thinkers who, with a background of present-day conceptions of the

nature of disease, might have been in the front rank of investigators

along these lines.

THE WAYS IN WHICH ARTHROPODS MAY AFFECT THE HEALTH OF MAN

When we consider the ways in which insects and their allies may affect

the health of man, we find that we may treat them under three main

groups:

A. They may be directly poisonous. Such, for example, are the scorpions,

certain spiders and mites, some of the predaceous bugs, and stinging

insects. Even such forms as the mosquito deserve some consideration from

this viewpoint.

B. They may be parasitic, living more or less permanently on or in the

body and deriving their sustenance from it.

Of the parasitic arthropods we may distinguish, first, the _true

parasites_, those which have adopted and become confirmed in the

parasitic habit. Such are the itch mites, the lice, fleas, and the

majority of the forms to be considered as parasitic.

In addition to these, we may distinguish a group of _accidental_, or

_facultative parasites_, species which are normally free-living, feeding

on decaying substances, but which when accidentally introduced into the

alimentary canal or other cavities of man, may exist there for a greater

or less period. For example, certain fly larvae, or maggots, normally

feeding in putrifying meat, have been known to occur as accidental or

facultative parasites in the stomach of man.

C. Finally, and most important, arthropods may be transmitters and

disseminators of disease. In this capacity they may function in one of

three ways; as _simple carriers_, as _direct inoculators_, or as

_essential hosts_ of disease germs.

As simple carriers, they may, in a wholly incidental manner, transport

from the diseased to the healthy, or from filth to food, pathogenic

germs which cling to their bodies or appendages. Such, for instance, is

the relation of the house-fly to the dissemination of typhoid.

As direct inoculators, biting or piercing species may take up from a

diseased man or animal, germs which, clinging to the mouth parts, are

inoculated directly into the blood of the insect's next victim. It it

thus that horse-flies may occasionally transmit anthrax. Similarly,

species of spiders and other forms which are ordinarily perfectly

harmless, may accidentally convey and inoculate pyogenic bacteria.

It is as essential hosts of disease germs that arthropods play their

most important role. In such cases an essential part of the life cycle

of the pathogenic organism is undergone in the insect. In other words,

without the arthropod host the disease-producing organism cannot

complete its development. As illustrations may be cited the relation of

the Anopheles mosquito to the malarial parasite, and the relation of the

cattle tick to Texas fever.

A little consideration will show that this is the most important of the

group. Typhoid fever is carried by water or by contaminated milk, and in

various other ways, as well as by the house-fly. Kill all the

house-flies and typhoid would still exist. On the other hand, malaria is

carried only by the mosquito, because an essential part of the

development of the malarial parasite is undergone in this insect.

Exterminate all of the mosquitoes of certain species and the

dissemination of human malaria is absolutely prevented.

Once an arthropod becomes an essential host for a given parasite it may

disseminate infection in three different ways:

1. By infecting man or animals who ingest it. It is thus, for example,

that man, dog, or cat, becomes infected with the double-pored dog

tapeworm, _Dipylidium caninum_. The cysticercoid stage occurs in the

dog louse, or in the dog or cat fleas, and by accidentally ingesting the

infested insect the vertebrate becomes infested. Similarly, _Hymenolepis

diminuta_, a common tapeworm of rats and mice, and occasional in man,

undergoes part of its life cycle in various meal-infesting insects, and

is accidentally taken up by its definitive host. It is very probable

that man becomes infested with _Dracunculus (Filaria) medinensis_

through swallowing in drinking water, the crustacean, _Cyclops_,

containing the larvae of this worm.

2. By infecting man or animals on whose skin or mucous membranes the

insect host may be crushed or may deposit its excrement. The pathogenic

organism may then actively penetrate, or may be inoculated by

scratching. The causative organism of typhus fever is thus transmitted

by the body louse.

3. By direct inoculation by its bite, the insect host may transfer the

parasite which has undergone development within it. The malarial

parasite is thus transferred by mosquitoes; the Texas fever parasite by

cattle ticks.

CHAPTER II.

ARTHROPODS WHICH ARE DIRECTLY POISONOUS

Of all the myriads of insects and related forms, a very few are of

direct use to man, some few others have forced his approbation on

account of their wonderful beauty, but the great hordes of them are

loathed or regarded as directly dangerous. As a matter of fact, only a

very small number are in the slightest degree poisonous to man or to the

higher animals. The result is that entomologists and lovers of nature,

intent upon dissipating the foolish dread of insects, are sometimes

inclined to go to the extreme of discrediting all statements of serious

injury from the bites or stings of any species.

Nevertheless, it must not be overlooked that poisonous forms do exist,

and they must receive attention in a consideration of the ways in which

arthropods may affect the health of man. Moreover, it must be recognized

that "what is one man's meat, is another man's poison," and that in

considering the possibilities of injury we must not ignore individual

idiosyncrasies. Just as certain individuals may be poisoned by what, for

others, are common articles of food, so some persons may be abnormally

susceptible to insect poison. Thus, the poison of a bee sting may be of

varying severity, but there are individuals who are made seriously sick

by a single sting, regardless of the point of entry. Some individuals

scarcely notice a mosquito bite, others find it very painful, and so

illustrations of this difference in individuals might be multiplied.

In considering the poisonous arthropods, we shall take them up by

groups. The reader who is unacquainted with the systematic relationship

of insects and their allies is referred to Chapter XII. No attempt will

be made to make the lists under the various headings exhaustive, but

typical forms will be discussed.

ARANEIDA OR SPIDERS

Of all the arthropods there are none which are more universally feared

than are the spiders. It is commonly supposed that the majority, if not

all the species are poisonous and that they are aggressive enemies of

man and the higher animals, as well as of lower forms.

That they really secrete a poison may be readily inferred from the

effect of their bite upon insects and other small forms. Moreover, the

presence of definite and well-developed poison glands can easily be

shown. They occur as a pair of pouches (fig. 1) lying within the

cephalothorax and connected by a delicate duct with a pore on the claw

of the chelicera, or so-called "mandible" on the convex surface of the

claw in such a position that it is not plugged and closed by the flesh

of the victim.

[Illustration: 1. Head of a spider showing poison gland (_c_) and its

relation to the chelicera (_a_).]

The glands may be demonstrated by slowly and carefully twisting off a

chelicera and pushing aside the stumps of muscles at its base. By

exercising care, the chitinous wall of the chelicera and its claw may be

broken away and the duct traced from the gland to its outlet. The inner

lining of the sac is constituted by a highly developed glandular

epithelium, supported by a basement membrane of connective tissue and

covered by a muscular layer, (fig. 2). The muscles, which are striated,

are spirally arranged (fig. 1), and are doubtless under control of the

spider, so that the amount of poison to be injected into a wound may be

varied.

[Illustration: 2. Section through a venom gland of Latrodectus

13-guttatus showing the peritoneal, muscular and epithelial layers.

After Bordas.]

The poison itself, according to Kobert (1901), is a clear, colorless

fluid, of oily consistency, acid reaction, and very bitter taste. After

the spider has bitten two or three times, its supply is exhausted and

therefore, as in the case of snakes, the poison of the bite decreases

quickly with use, until it is null. To what extent the content of the

poison sacs may contain blood serum or, at least, active principles of

serum, in addition to a specific poison formed by the poison glands

themselves, Kobert regards as an open question. He believes that the

acid part of the poison, if really present, is formed by the glands and

that, in the case of some spiders, the ferment-like, or better, active

toxine, comes from the blood.

[Illustration: 3. Chelicera of a spider.]

But there is a wide difference between a poison which may kill an insect

and one which is harmful to men. Certain it is that there is no lack of

popular belief and newspaper records of fatal cases, but the evidence

regarding the possibility of fatal or even very serious results for man

is most contradictory. For some years, we have attempted to trace the

more circumstantial newspaper accounts, which have come to our notice,

of injury by North American species. The results have served, mainly, to

emphasize the straits to which reporters are sometimes driven when there

is a dearth of news. The accounts are usually vague and lacking in any

definite clue for locating the supposed victim. In the comparatively few

cases where the patient, or his physician, could be located, there was

either no claim that the injury was due to spider venom, or there was no

evidence to support the belief. Rarely, there was evidence that a

secondary blood poisoning, such as might be brought about by the prick

of a pin, or by any mechanical injury, had followed the bite of a

spider. Such instances have no bearing on the question of the venomous

nature of these forms.

[Illustration: 4. The Italian tarantula (Lycosa tarantula). After

Kobert.]

The extreme to which unreasonable fear of the bites of spiders

influenced the popular mind was evidenced by the accepted explanation of

the remarkable dancing mania, or tarantism, of Italy during the Middle

Ages. This was a nervous disorder, supposed to be due to the bite of a

spider, the European tarantula (fig. 4), though it was also, at times,

attributed to the bite of the scorpion. In its typical form, it was

characterized by so great a sensibility to music that under its

influence the victims indulged in the wildest and most frenzied dancing,

until they sank to the ground utterly exhausted and almost lifeless. The

profuse perspiring resulting from these exertions was supposed to be the

only efficacious remedy for the disease. Certain forms of music were

regarded as of especial value in treating this tarantism, and hence the

name of "tarantella" was applied to them. Our frontispiece, taken from

Athanasius Kircher's _Magnes sive de Arte Magnetica_, 1643 ed.,

represents the most commonly implicated spider and illustrates some of

what Fabre has aptly designated as "medical choreography."

The disease was, in reality, a form of hysteria, spreading by sympathy

until whole communities were involved, and was paralleled by the

outbreaks of the so-called St. Vitus's or St. John's dance, which swept

Germany at about the same time (fig. 5). The evidence that the spider

was the cause of the first is about as conclusive as is that of the

demoniacal origin of the latter. The true explanation of the outbreaks

is doubtless to be found in the depleted physical and mental condition

of the people, resulting from the wars and the frightful plagues which

devastated all Europe previous to, and during these times. An

interesting discussion of these aspects of the question is to be found

in Hecker.

[Illustration: 5. Dancing mania. Illustration from Johann Ludwig

Gottfried's Chronik. 1632.]

So gross has been the exaggeration and so baseless the popular fear

regarding spiders that entomologists have been inclined to discredit all

accounts of serious injury from their bites. Not only have the most

circumstantial of newspaper accounts proved to be without foundation but

there are on record a number of cases where the bite of many of the

commoner species have been intentionally provoked and where the effect

has been insignificant. Some years ago the senior author personally

experimented with a number of the largest of our northern species, and

with unexpected results. The first surprise was that the spiders were

very unwilling to bite and that it required a considerable effort to get

them to attempt to do so. In the second place, most of those

experimented with were unable to pierce the skin of the palm or the back

of the hand, but had to be applied to the thin skin between the fingers

before they were able to draw blood. Unfortunately, no special attempt

was made to determine, at the time, the species experimented with, but

among them were _Theridion tepidariorum_, _Miranda aurantia_

(_Argiopa_), _Metargiope trifasciata_, _Marxia stellata_, _Aranea

trifolium_, _Misumena vatia_, and _Agelena naevia_. In no case was the

bite more severe than a pin prick and though in some cases the sensation

seemed to last longer, it was probably due to the fact that the mind was

intent upon the experiment.

[Illustration: 6. An American tarantula (Eurypelma hentzii). Natural

size. After Comstock.]

Similar experiments were carried out by Blackwell (1855), who believed

that in the case of insects bitten, death did not result any more

promptly than it would have from a purely mechanical injury of equal

extent. He was inclined to regard all accounts of serious injury to man

as baseless. The question cannot be so summarily dismissed, and we shall

now consider some of the groups which have been more explicitly

implicated.

THE TARANTULAS.--In popular usage, the term "tarantula" is loosely

applied to any one of a number of large spiders. The famous tarantulas

of southern Europe, whose bites were supposed to cause the dancing

mania, were Lycosidae, or wolf-spiders. Though various species of this

group were doubtless so designated, the one which seems to have been

most implicated was _Lycosa tarantula_ (L.), (fig. 4). On the other

hand, in this country, though there are many Lycosidae, the term

"tarantula" has been applied to members of the superfamily Avicularoidea

(fig. 6), including the bird-spiders.

Of the Old World Lycosidae there is no doubt that several species were

implicated as the supposed cause of the tarantism. In fact, as we have

already noted, the blame was sometimes attached to a scorpion. However,

there seems to be no doubt that most of the accounts refer to the spider

known as _Lycosa tarantula_.

There is no need to enter into further details here regarding the

supposed virulence of these forms, popular and the older medical

literature abound in circumstantial accounts of the terrible effects of

the bite. Fortunately, there is direct experimental evidence which bears

on the question.

Fabre induced a common south European wolf-spider, _Lycosa narbonensis_,

to bite the leg of a young sparrow, ready to leave the nest. The leg

seemed paralyzed as a result of the bite, and though the bird seemed

lively and clamored for food the next day, on the third day it died. A

mole, bitten on the nose, succumbed after thirty-six hours. From these

experiments Fabre seemed justified in his conclusion that the bite of

this spider is not an accident which man can afford to treat lightly.

Unfortunately, there is nothing in the experiments, or in the symptoms

detailed, to exclude the probability that the death of the animals was

the result of secondary infection.

As far back as 1693, as we learn from the valuable account of Kobert,

(1901), the Italian physician, Sanguinetti allowed himself to be bitten

on the arm by two tarantulas, in the presence of witnesses. The

sensation was equivalent to that from an ant or a mosquito bite and

there were no other phenomena the first day. On the second day the wound

was inflamed and there was slight ulceration. It is clear that these

later symptoms were due to a secondary infection. These experiments have

been repeated by various observers, among whom may be mentioned Leon

Dufour, Josef Erker and Heinzel, and with the similar conclusion that

the bite of the Italian tarantula ordinarily causes no severe symptoms.

In this conclusion, Kobert, though firmly convinced of the poisonous

nature of some spiders, coincides. He also believes that striking

symptoms may be simulated or artificially induced by patients in order

to attract interest, or because they have been assured that the bite,

under all circumstances, caused tarantism.

The so-called Russian tarantula, _Trochosa singoriensis_ (fig. 7), is

much larger than the Italian species, and is much feared. Kobert carried

out a series of careful experiments with this species and his results

have such an important bearing on the question of the venomous nature of

the tarantula that we quote his summary. Experimenting first on nearly a

hundred living specimens of _Trochosa singoriensis_ from Crimea he says

that:

"The tarantulas, no matter how often they were placed on the skin,

handled, and irritated, could not be induced to bite either myself, the

janitor, or the ordinary experimental animals. The objection that the

tarantulas were weak and indifferent cannot stand, for as soon as I

placed two of them on the shaved skin of a rabbit, instead of an attack

on the animal, there began a furious battle between the two spiders,

which did not cease until one of the two was killed."

[Illustration: 7. Trochosa singoriensis. After Kobert.]

"Since the spiders would not bite, I carefully ground up the fresh

animals in physiological salt solution, preparing an extract which must

have contained, in solution, all of the poisonous substance of their

bodies. While in the case of _Latrodectus_, as we shall see, less than

one specimen sufficed to yield an active extract, I have injected the

filtered extract of six fresh Russian tarantulas, of which each one was

much heavier than an average _Latrodectus_, subcutaneously and into the

jugular vein of various cats without the animals dying or showing any

special symptoms. On the basis of my experiments I can therefore only

say that the quantity of the poison soluble in physiological salt

solution, even when the spiders are perfectly fresh and well nourished,

is very insignificant. That the poison of the Russian tarantula is not

soluble in physiological salt solution, is exceedingly improbable.

Moreover, I have prepared alcoholic extracts and was unable to find them

active. Since the Russian spider exceeds the Italian in size and in

intensity of the bite, it seems very improbable to me that the

pharmacological test of the Italian tarantula would yield essentially

other results than those from the Russian species."

To the AVICULAROIDEA belong the largest and most formidable appearing of

the spiders and it is not strange that in the New World they have fallen

heir to the bad reputation, as well as to the name of the tarantula of

Europe. In this country they occur only in the South or in the far West,

but occasionally living specimens are brought to our northern ports in

shipments of bananas and other tropical produce, and are the source of

much alarm. It should be mentioned, however, that the large spider most

frequently found under such circumstances is not a tarantula at all, but

one of the Heteropodidae, or giant crab-spiders, (fig. 8).

[Illustration: 8. The giant crab-spider or banana spider (Heteropoda

venatoria). Natural size. After Comstock.]

In spite of their prominence and the fear which they arouse there are

few accurate data regarding these American tarantulas. It has often been

shown experimentally that they can kill small birds and mammals, though

it is doubtful if these form the normal prey of any of the species, as

has been claimed. There is no question but that the mere mechanical

injury which they may inflict, and the consequent chances of secondary

infection, justify, in part, their bad reputation. In addition to the

injury from their bite, it is claimed that the body hairs of several of

the South American species are readily detached and are urticating.

Recently, Phisalix (1912) has made a study of the physiological effects

of the venom of two Avicularoidea, _Phormictopus carcerides_ Pocock,

from Haiti and _Cteniza sauvagei_ Rossi, from Corsica. The glands were

removed aseptically and ground up with fine, sterilized sand in

distilled water. The resultant liquid was somewhat viscid, colorless,

and feebly alkaline. Injected into sparrows and mice the extract of

_Phormictopus_ proved very actively poisonous, that from a single spider

being sufficient to kill ten sparrows or twenty mice. It manifested

itself first and, above all, as a narcotic, slightly lowering the

temperature and paralyzing the respiration. Muscular and cardiac

weakening, loss of general sensibility, and the disappearance of

reflexes did not occur until near the end. The extract from _Cteniza_

was less active and, curiously enough, the comparative effect on

sparrows and on mice was just reversed.

SPIDERS OF THE GENUS LATRODECTUS.--While most of the popular accounts of

evil effects from the bites of spiders will not stand investigation, it

is a significant fact that, the world over, the best authenticated

records refer to a group of small and comparatively insignificant

spiders belonging to the genus _Latrodectus_, of the family Theridiidae.

The dread "Malmigniatte" of Corsica and South Europe, the "Karakurte" of

southeastern Russia, the "Katipo" of New Zealand, the "Mena-vodi" and

"Vancoho" of Madagascar, and our own _Latrodectus mactans_, all belong

to this genus, and concerning all of these the most circumstantial

accounts of their venomous nature are given. These accounts are not mere

fantastic stories by uneducated natives but in many cases are reports

from thoroughly trained medical men.

The symptoms produced are general, rather than local. As summarized by

Kobert (1901) from a study of twenty-two cases treated in 1888, in the

Kherson (Russia) Government Hospital and Berislaw (Kherson) District

Hospital the typical case, aside from complications, exhibits the

following symptoms. The victim suddenly feels the bite, like the sting

of a bee. Swelling of the barely reddened spot seldom follows. The

shooting pains, which quickly set in, are not manifested at the point of

injury but localized at the joints of the lower limb and in the region

of the hip. The severity of the pain forces the victim to the hospital,

in spite of the fact that they otherwise have a great abhorrence of it.

The patient is unable to reach the hospital afoot, or, at least, not

without help, for there is usually inability to walk. The patient, even

if he has ridden, reaches the hospital covered with cold sweat and

continues to perspire for a considerable period. His expression

indicates great suffering. The respiration may be somewhat dyspnoeic,

and a feeling of oppression in the region of the heart is common. There

is great aversion to solid food, but increasing thirst for milk and tea.

Retention of urine, and constipation occur. Cathartics and, at night,

strong narcotics are desired. Warm baths give great relief. After three

days, there is marked improvement and usually the patient is dismissed

after the fifth. This summary of symptoms agrees well with other

trustworthy records.

It would seem, then, that Riley and Howard (1889), who discussed a

number of accounts in the entomological literature, were fully justified

in their statement that "It must be admitted that certain spiders of the

genus _Latrodectus_ have the power to inflict poisonous bites, which may

(probably exceptionally and depending upon exceptional conditions) bring

about the death of a human being."

And yet, until recently the evidence bearing on the question has been

most conflicting. The eminent arachnologist, Lucas, (1843) states that

he himself, had been repeatedly bitten by the Malmigniatte without any

bad effects. Dr. Marx, in 1890, gave before the Entomological Society of

Washington, an account of a series of experiments to determine whether

the bite of _Latrodectus mactans_ is poisonous or not. He described the

poison glands as remarkably small[A] and stated that he had introduced

the poison in various ways into guinea-pigs and rabbits without

obtaining any satisfactory results. Obviously, carefully conducted

experiments with the supposed venom were needed and fortunately they

have been carried out in the greatest detail by Kobert (1901).

This investigator pointed out that there were two factors which might

account for the discrepancies in the earlier experiments. In the first

place, the poison of spiders, as of snakes, might be so exhausted after

two or three bites that further bites, following directly, might be

without visible effect. Secondly, the application of the poison by means

of the bite, is exceedingly inexact, since even after the most careful

selection of the point of application, the poison might in one instance

enter a little vein or lymph vessel, and in another case fail to do so.

Besides, there would always remain an incalculable and very large amount

externally, in the nonabsorptive epithelium. While all of these factors

enter into the question of the effect of the bite in specific instances,

they must be as nearly as possible obviated in considering the question

of whether the spiders really secrete a venom harmful to man.

Kobert therefore sought to prepare extracts which would contain the

active principles of the poison and which could be injected in definite

quantities directly into the blood of the experimental animal. For this

purpose various parts of the spiders were rubbed up in a mortar with

distilled water, or physiological salt solution, allowed to stand for an

hour, filtered, and then carefully washed, by adding water drop by drop

for twenty-four hours. The filtrate and the wash-water were then united,

well mixed and, if necessary, cleared by centrifuging or by exposure to

cold. The mixture was again filtered, measured, and used, in part, for

injection and, in part, for the determination of the organic materials.

Such an extract was prepared from the cephalothoraces of eight dried

specimens of the Russian _Latrodectus_ and three cubic centimeters of

this, containing 4.29 mg. of organic material, were injected into the

jugular vein of a cat weighing 2450 grams. The previously very active

animal was paralyzed and lay in whatever position it was placed. The

sensibility of the skin of the extremities and the rump was so reduced

that there was no reaction from cutting or sticking. There quickly

followed dyspnoea, convulsions, paralysis of the respiratory muscles

and of the heart. In twenty-eight minutes the cat was dead, after having

exhibited exactly the symptoms observed in severe cases of poisoning of

man from the bite of this spider.

These experiments were continued on cats, dogs, guinea pigs and various

other animals. Not only extracts from the cephalothorax, but from other

parts of the body, from newly hatched spiders, and from the eggs were

used and all showed a similar virulence. Every effort was made to avoid

sources of error and the experiments, conducted by such a recognized

authority in the field of toxicology, must be accepted as conclusively

showing that this spider and, presumably, other species of the genus

_Latrodectus_ against which the clinical evidence is quite parallel,

possess a poison which paralyzes the heart and central nervous system,

with or without preliminary stimulus of the motor center. If the

quantity of the poison which comes into direct contact with the blood is

large, there may occur haemolysis and thrombosis of the vessels.

On the other hand, check experiments were carried out, using similar

extracts of many common European spiders of the genera _Tegenaria_,

_Drassus_, _Agelena_, _Eucharia_ and _Argyroneta_, as well as the

Russian tarantula, _Lycosa singoriensis_. In no other case was the

effect on experimental animals comparable to the _Latrodectus_ extract.

Kobert concludes that in its chemical nature the poison is neither an

alkaloid, nor a glycoside, nor an acid, but a toxalbumen, or poisonous

enzyme which is very similar to certain other animal poisons, notably

that of the scorpion.

[Illustration: 9. Latrodectus mactans; (_a_) female, x3; (_b_) venter

of female; (_c_) dorsum of male. After Comstock.]

The genus _Latrodectus_ is represented in the United States by at least

two species, _L. mactans_ and _L. geometricus_. Concerning _L. mactans_

there are very circumstantial accounts of serious injury and even death

in man[B]. _Latrodectus mactans_ is coal black, marked with red or

yellow or both. It has eight eyes, which are dissimilar in color and

are distinctly in front of the middle of the thorax, the lateral eyes of

each side widely separate. The tarsus of the fourth pair of legs has a

number of curved setae in a single series. It has on the ventral side of

its abdomen an hour-glass shaped spot. The full-grown female is about

half an inch in length. Its globose abdomen is usually marked with one

or more red spots dorsally along the middle line. The male is about half

as long but has in addition to the dorsal spots, four pairs of stripes

along the sides. Immature females resemble the male in coloring (fig.

9).

Regarding the distribution of _Latrodectus mactans_, Comstock states

that: "Although it is essentially a Southern species, it occurs in

Indiana, Ohio, Pennsylvania, New Hampshire, and doubtless other of the

Northern States." _L. geometricus_ has been reported from California.

OTHER VENOMOUS SPIDERS--While conclusive evidence regarding the venomous

nature of spiders is meager and relates almost wholly to that of the

genus _Latrodectus_, the group is a large one and we are not justified

in dismissing arbitrarily, all accounts of injury from their bites.

Several species stand out as especially needing more detailed

investigation.

_Chiracanthium nutrix_ is a common European species of the family

Clubionidae, concerning which there is much conflicting testimony. Among

the reports are two by distinguished scientists whose accounts of

personal experiences cannot be ignored. A. Forel allowed a spider of

this species to bite him and not only was the pain extreme, but the

general symptoms were so severe that he had to be helped to his house.

The distinguished arachnologist, Bertkau reports that he, himself, was

bitten and that an extreme, burning pain spread almost instantaneously

over the arm and into the breast. There were slight chills the same day

and throbbing pain at the wound lasted for days. While this particular

species is not found in the United States, there are two other

representatives of the genus and it is possible that they possess the

same properties. We are unaware of any direct experimental work on the

poison.

_Epeira diadema_, of Europe, belongs to a wholly different group, that

of the orb-weavers, but has long been reputed venomous. Kobert was able

to prepare from it an extract whose effects were very similar to that

prepared from _Latrodectus_, though feebler in its action. Under

ordinary circumstances this spider is unable to pierce the skin of man

and though Kobert's results seem conclusive, the spider is little to be

feared.

_Phidippus audax_ (_P. tripunctatus_) is one of our largest Attids, or

jumping spiders. The late Dr. O. Lugger describes a case of severe

poisoning from the bite of this spider and though details are lacking,

it is quite possible that this and other large species of the same

group, which stalk their prey, may possess a more active poison than

that of web-building species.

SUMMARY--It is clearly established that our common spiders are not to be

feared and that the stories regarding their virulence are almost wholly

without foundation. On the other hand, the chances of secondary

infection from the bites of some of the more powerful species are not to

be ignored.

Probably all species possess a toxin secreted by the poison gland,

virulent for insects and other normal prey of the spiders, but with

little or no effect on man.

There are a very few species, notably of the genus _Latrodectus_, and

possibly including the European _Chiracanthium nutrix_ and _Epeira

diadema_, which possess, in addition, a toxalbumen derived from the

general body tissue, which is of great virulence and may even cause

death in man and the higher animals.

[Illustration: 10. A whip-scorpion (Mastigoproctus giganteus). Half

natural size. After Comstock.]

THE PEDIPALPIDA OR WHIP-SCORPIONS

The tailed whip-scorpions, belonging to the family Thelyphonidae, are

represented in the United States by the giant whip-scorpion

_Mastigoproctus giganteus_ (fig. 10), which is common in Florida, Texas

and some other parts of the South. In Florida, it is locally known as

the "grampus" or "mule-killer" and is very greatly feared. There is no

evidence that these fears have any foundation, and Dr. Marx states that

there is neither a poison gland nor a pore in the claw of the

chelicera.

THE SCORPIONIDA, OR TRUE SCORPIONS

The true scorpions are widely distributed throughout warm countries and

everywhere bear an evil reputation. According to Comstock (1912), about

a score of species occur in the Southern United States. These are

comparatively small forms but in the tropics members of this group may

reach a length of seven or eight inches. They are pre-eminently

predaceous forms, which lie hidden during the day and seek their prey by

night.

[Illustration: 11. A true scorpion. After Comstock.]

The scorpions (fig. 11) possess large pedipalpi, terminated by strongly

developed claws, or chelae. They may be distinguished from all other

Arachnids by the fact that the distinctly segmented abdomen is divided

into a broad basal region of seven segments and a terminal, slender,

tail-like division of five distinct segments.

The last segment of the abdomen, or telson, terminates in a

ventrally-directed, sharp spine, and contains a pair of highly developed

poison glands. These glands open by two small pores near the tip of the

spine. Most of the species when running carry the tip of the abdomen

bent upward over the back, and the prey, caught and held by the

pedipalpi, is stung by inserting the spine of the telson and allowing it

to remain for a time in the wound.

The glands themselves have been studied in _Prionurus citrinus_ by

Wilson (1904). He found that each gland is covered by a sheet of muscle

on its mesal and dorsal aspects, which may be described as the

_compressor muscle_. The muscle of each side is inserted by its edge

along the ventral inner surface of the chitinous wall of the telson,

close to the middle line, and by a broader insertion laterally. A layer

of fine connective tissue completely envelops each gland and forms the

basis upon which the secreting cells rest. The secreting epithelium is

columnar; and apparently of three different types of cells.

1. The most numerous have the appearance of mucous cells, resembling the

goblet cells of columnar mucous membranes. The nucleus, surrounded by a

small quantity of protoplasm staining with haematoxylin, lies close to

the base of the cell.

2. Cells present in considerable numbers, the peripheral portions of

which are filled with very numerous fine granules, staining with acid

dyes such as methyl orange.

3. Cells few in number, filled with very large granules, or irregular

masses of a substance staining with haematoxylin.

The poison, according to Kobert (1893), is a limpid, acid-reacting

fluid, soluble in water but insoluble in absolute alcohol and ether.

There are few data relative to its chemical nature. Wilson (1901) states

that a common Egyptian species, _Buthus quinquestriatus_, has a specific

gravity of 1.092, and contains 20.3% of solids and 8.4% ash.

The venom of different species appears to differ not only quantitatively

but qualitatively. The effects of the bite of the smaller species of the

Southern United States may be painful but there is no satisfactory

evidence that it is ever fatal. On the other hand, certain tropical

species are exceedingly virulent and cases of death of man from the bite

are common.

In the case of _Buthus quinquestriatus_, Wilson (1904) found the

symptoms in animals to be hypersecretion, salivation and lachrymation,

especially marked, convulsions followed by prolonged muscular spasm;

death from asphyxia. The temperature shows a slight, rarely

considerable, rise. Rapid and considerable increase of blood-pressure

(observed in dogs) is followed by a gradual fall with slowing of the

heart-beat. The coagulability of the blood is not affected.

An interesting phase of Wilson's work was the experiments on desert

mammals. The condition under which these animals exist must frequently

bring them in contact with scorpions, and he found that they possess a

degree of immunity to the venom sufficient at least to protect them from

the fatal effects of the sting.

As far as concerns its effect on man, Wilson found that much depended

upon the age. As high as 60 per cent of the cases of children under

five, resulted fatally. Caroroz (1865), states that in a Mexican state

of 15,000 inhabitants, the scorpions were so abundant and so much feared

that the authorities offered a bounty for their destruction. A result

was a large number of fatalities, over two hundred per year. Most of the

victims were children who had attempted to collect the scorpions.

The treatment usually employed in the case of bites by the more

poisonous forms is similar to that for the bite of venomous snakes.

First, a tight ligature is applied above the wound so as to stop the

flow of blood and lymph from that region. The wound is then freely

excised and treated with a strong solution of permanganate of potash, or

with lead and opium lotion.

In recent years there have been many attempts to prepare an antivenom,

or antiserum comparable to what has been used so effectively in the case

of snake bites. The most promising of these is that of Todd (1909),

produced by the immunization of suitable animals. This antivenom proved

capable of neutralizing the venom when mixed _in vitro_ and also acts

both prophylactically and curatively in animals. Employed curatively in

man, it appears to have a very marked effect on the intense pain

following the sting, and the evidence so far indicates that its prompt

use greatly reduces the chance of fatal results.

THE SOLPUGIDA, OR SOLPUGIDS

The SOLPUGIDA are peculiar spider-like forms which are distinguished

from nearly all other arachnids by the fact that they possess no true

cephalothorax, the last two leg-bearing segments being distinct,

resembling those of the abdomen in this respect. The first pair of legs

is not used in locomotion but seemingly functions as a second pair of

pedipalpi. Figure 12 illustrates the striking peculiarities of the

group. They are primarily desert forms and occur in the warm zones of

all countries. Of the two hundred or more species, Comstock lists twelve

as occurring in our fauna. These occur primarily in the southwest.

[Illustration: 12. A solpugid (Eremobates cinerea). After Comstock.]

The Solpugida have long borne a bad reputation and, regarding virulence,

have been classed with the scorpions. Among the effects of their bites

have been described painful swelling, gangrene, loss of speech, cramps,

delirium, unconsciousness and even death. Opposed to the numerous loose

accounts of poisoning, there are a number of careful records by

physicians and zoologists which indicate clearly that the effects are

local and though they may be severe, they show not the slightest symptom

of direct poisoning.

More important in the consideration of the question is the fact that

there are neither poison glands nor pores in the fangs for the exit of

any poisonous secretion. This is the testimony of a number of prominent

zoologists, among whom is Dr. A. Walter, who wrote to Kobert at length

on the subject and whose conclusions are presented by him.

However, it should be noted that the fangs are very powerful and are

used in such a manner that they may inflict especially severe wounds.

Thus, there may be more opportunity for secondary infection than is

usual in the case of insect wounds.

The treatment of the bite of the Solpugida is, therefore, a matter of

preventing infection. The wound should be allowed to bleed freely and

then washed out with a 1:3000 solution of corrosive sublimate, and, if

severe, a wet dressing of this should be applied. If infection takes

place, it should be treated in the usual manner, regardless of its

origin.

THE ACARINA, OR MITES AND TICKS

A number of the parasitic Acarina evidently secrete a specific poison,

presumably carried by the saliva, but in most cases its effect on man is

insignificant. There is an abundant literature dealing with the

poisonous effect of the bite of these forms, especially the ticks, but

until recently it has been confused by failure to recognize that various

species may transmit diseases of man, rather than produce injury through

direct poisoning. We shall therefore discuss the Acarina more especially

in subsequent chapters, dealing with parasitism and with disease

transmission.

Nevertheless, after the evidence is sifted, there can be no doubt that

the bites of certain ticks may occasionally be followed by a direct

poisoning, which may be either local or general in its effects. Nuttall

(1908) was unable to determine the cause of the toxic effect, for, in

_Argas persicus_, the species most often implicated, he failed to get

the slightest local or general effect on experimental animals, from the

injection of an emulsion prepared by crushing three of the ticks.

It seems clearly established that the bite of certain ticks may cause a

temporary paralysis, or even complete paralysis, involving the organs of

respiration or the heart, and causing death. In 1912, Dr. I. U. Temple,

of Pendleton, Oregon, reported several cases of what he called "acute

ascending paralysis" associated with the occurrence of ticks on the head

or the back of the neck. A typical severe case was that of a six year

old child, who had retired in her usual normal health. The following

morning upon arising she was unable to stand on her feet. She exhibited

paralysis extending to the knees, slight temperature, no pain, sensory

nerves normal, motor nerves completely paralyzed, reflexes absent. The

following day the paralysis had extended to the upper limbs, and before

night of the third day the nerves of the throat (hypoglossal) were

affected. The thorax and larynx were involved, breathing was labored,

she was unable to swallow liquids, phonation was impossible and she

could only make low, guttural sounds. At this stage, two ticks, fully

distended with blood, were found over the junction of the spinal column

with the occipital bones in the hollow depression. They were removed by

the application of undiluted creoline. Though the child's life was

despaired of, by the following morning she was very much improved. By

evening she was able to speak. The paralysis gradually receded,

remaining longest in the feet, and at the end of one week the patient

was able to go home.

There was some doubt as to the exact species of tick implicated in the

cases which Dr. Temple reported, although the evidence pointed strongly

to _Dermacentor venustus_.[C] Somewhat later, Hadwen (1913) reported

that "tick paralysis" occurs in British Columbia, where it affects not

only man, but sheep and probably other animals. It is caused by the

bites of _Dermacentor venustus_ and was experimentally produced in lambs

and a dog (Hadwen and Nuttall, 1913). It is only when the tick begins to

engorge or feed rapidly, some days after it has become attached, that

its saliva produces pathogenic effects.

Ulceration following tick bite is not uncommon. In many of the instances

it is due to the file-like hypostome, with its recurved teeth, being

left in the wound when the tick is forcibly pulled off.

THE MYRIAPODA, OR CENTIPEDES AND MILLIPEDES

The old class, Myriapoda includes the DIPLOPODA, or millipedes, and the

CHILOPODA, or centipedes. The present tendency is to raise these groups

to the rank of classes.

The Diplopoda

The DIPLOPODA, or millipedes (fig. 13), are characterized by the

presence of two pairs of legs to a segment. The largest of our local

myriapods belong to this group. They live in moist places, feeding

primarily on decaying vegetable matter, though a few species

occasionally attack growing plants.

[Illustration: 13. A millipede. After Comstock.]

The millipedes are inoffensive and harmless. _Julus terrestris_, and

related species, when irritated pour out over the entire body a

yellowish secretion which escapes from cutaneous glands. It is volatile,

with a pungent odor, and Phisalix (1900) has shown that it is an active

poison when injected into the blood of experimental animals. This,

however, does not entitle them to be considered as poisonous arthropods,

in the sense of this chapter, any more than the toad can be considered

poisonous to man because it secretes a venom from its cutaneous glands.

The Chilopoda

[Illustration: 14. Two common centipedes.

(_a_) Lithobius forficatus. After Comstock.

(_b_) Scutigera forceps. Natural size; after Howard.]

The CHILOPODA, or centipedes (fig. 14), unlike the millipedes, are

predaceous forms, and possess well developed poison glands for killing

their prey. These glands are at the base of the first pair of legs

(fig. 15), which are bent forward so as to be used in holding their

prey. The legs terminate in a powerful claw, at the tip of which is the

outlet of the poison glands.

The poison is a limpid, homogeneous, slightly acid fluid, which

precipitates in distilled water. Briot (1904) extracted it from the

glands of _Scolopendra morsitans_, a species common in central France,

and found that it was actively venomous for the ordinary experimental

animals. A rabbit of two kilograms weight received an injection of three

cubic centimeters in the vein of the ear and died in a minute. A white

rat, weighing forty-eight grams, received one and a half cubic

centimeters in the hind leg. There was an almost immediate paralysis of

the leg and marked necrosis of the tissues.

[Illustration: 15. Mandible of Scolopendra cingulata showing venom

gland. After Dubosq.]

As for the effect on man, there is little foundation for the fear with

which centipedes are regarded. Our native species produce, at most,

local symptoms,--sometimes severe local pain and swelling,--but there is

no authentic record of fatal results. In the tropics, some of the

species attain a large size, _Scolopendra gigantea_ reaching a length of

nearly a foot. These forms are justly feared, and there is good evidence

that death sometimes, though rarely, results from their bite.

One of the most careful accounts of death from the sting of the scorpion

is that of Linnell, (1914), which relates to a comparatively small

Malayan species, unfortunately undetermined. The patient, a coolie, aged

twenty, was admitted to a hospital after having been stung two days

previously on the left heel. For cure, the other coolies had made him

eat the head of the scorpion. On admission, the patient complained of

"things creeping all over the body". Temp. 102.8^o. On the fourth day he

had paralysis of the legs, and on the fifth day motor paralysis to the

umbilicus, sensation being unaltered. On the sixth day there was

retention of the urine and on the ninth day (first test after third day)

sugar was present. On the thirteenth day the patient became comatose,

but could be roused to eat and drink. The temperature on the following

day fell below 95^o and the patient was still comatose. Death fifteenth

day.

Examination of the spinal (lumbar) cord showed acute disseminated

myelitis. In one part there was an acute destruction of the anterior

horn and an infiltration of round cells. In another portion Clarke's

column had been destroyed. The perivascular sheaths were crowded with

small round cells and the meninges were congested. Some of the cells of

the anterior horn were swollen and the nuclei eccentric; chromatolysis

had occurred in many of them.

As for treatment, Castellani and Chalmers (1910), recommend bathing the

part well with a solution of ammonia (one in five, or one in ten). After

bathing, apply a dressing of the same alkali or, if there is much

swelling and redness, an ice-bag. If necessary, hypodermic injections of

morphine may be given to relieve the pain. At a later period

fomentations may be required to reduce the local inflammation.

THE HEXAPODA OR TRUE INSECTS

There are a number of HEXAPODA, or true insects, which are, in one way

or another, poisonous to man. These belong primarily to the orders

Hemiptera, or true bugs; Lepidoptera, or butterflies and moths (larval

forms); Diptera, or flies; Coleoptera, or beetles; and Hymenoptera, or

ants, bees, and wasps. There are various ways in which they may be

poisonous.

1. _Piercing_ or _biting_ forms may inject an irritating or poisonous

saliva into the wound caused by their mouth-parts.

2. _Stinging forms_ may inject a poison, from glands at the caudal end

of the abdomen, into wounds produced by a specially modified ovipositer,

the _sting_.

3. _Nettling_ properties may be possessed by the hairs of the insect.

4. _Vescicating_, or _poisonous blood plasma_, or _body fluids_ are

known to exist in a large number of species and may, under exceptional

circumstances, affect man.

For convenience of discussion, we shall consider poisonous insects under

these various headings. In this, as in the preceding discussion, no

attempt will be made to give an exhaustive list of the poisonous forms.

Typical instances will be selected and these will be chosen largely from

North American species.

PIERCING OR BITING INSECTS POISONOUS TO MAN

HEMIPTERA

Several families of the true bugs include forms which, while normally

inoffensive, are capable of inflicting painful wounds on man. In these,

as in all of the Hemiptera, the mouth-parts are modified to form an

organ for piercing and sucking. This is well shown by the accompanying

illustration (fig. 16).

The upper lip, or _labrum_, is much reduced and immovable, the lower

lip, or _labium_, is elongated to form a jointed sheath, within which

the lance-like mandibles and maxillae are enclosed. The mandibles are

more or less deeply serrate, depending on the species concerned.

[Illustration: 16. Beak of hemipteron.]

The poison is elaborated by the salivary glands, excepting, possibly, in

_Belostoma_ where Locy is inclined to believe that it is secreted by the

maxillary glands. The salivary glands of the Hemiptera have been the

subject of much study but the most recent, comprehensive work has been

done by Bugnion and Popoff, (1908 and 1910) to whose text the reader is

referred for details.

The Hemiptera have two pairs of salivary glands: the _primary gland_, of

which the efferent duct leads to the salivary syringe, and the

_accessory gland_, of which the very long and flexuous duct empties into

the primary duct at its point of insertion. Thus, when one observes the

isolated primary gland it appears as though it had efferent ducts

inserted at the same point. In _Nepa_ and the _Fulgoridae_ there are two

accessory glands and therefore apparently three ducts at the same point

on the primary gland. The _ensemble_ differs greatly in appearance in

different species but we shall show here Bugnion and Popoff's figure of

the apparatus of _Notonecta maculata_, a species capable of inflicting a

painful bite on man (fig. 17).

[Illustration: 17. Salivary glands of Notonecta maculata. After Bugnion

and Popoff.]

[Illustration: 18. Pharyngeal syringe or salivary pump of Fulgora

maculata. After Bugnion and Popoff.]

[Illustration: 19. Heteroptera, (_a_) Melanolestes picipes; (_b_)

Notonecta undulata; (_c_, _d_) Aradus robustus (_c_) adult, (_d_) nymph,

much enlarged; (_e_) Arilus cristatus; (_f_) Belostoma americana; (_g_)

Nabis (Coriscus) subcoleoptratus, enlarged; (_h_) Cimex lectularius,

(_i_) Oeciacus vicarius, much enlarged; (_j_) Lyctocoris fitchii, much

enlarged. After Lugger.]

Accessory to the salivary apparatus there is on the ventral side of the

head, underneath the pharynx, a peculiar organ which the Germans have

called the "Wanzenspritze," or syringe. The accompanying figure of the

structure in _Fulgora maculata_ (fig. 18) shows its relation to the

ducts of the salivary glands and to the beak. It is made up of a

dilatation forming the body of the pump, in which there is a chitinous

piston. Attached to the piston is a strong retractor muscle. The

function of the salivary pump is to suck up the saliva from the salivary

ducts and to force it out through the beak.

Of the Hemiptera reported as attacking man, we shall consider briefly

the forms most frequently noted.

The NOTONECTIDAE, or _back swimmers_, (fig. 19_b_) are small, aquatic

bugs that differ from all others in that they always swim on their

backs. They are predaceous; feeding on insects and other small forms.

When handled carelessly they are able to inflict a painful bite, which

is sometimes as severe as the sting of a bee. In fact, they are known in

Germany as "Wasserbienen."

The BELOSTOMATIDAE, or _giant water bugs_, (fig. 19_f_) include the

largest living Hemiptera. They are attracted to lights and on account of

the large numbers which swarm about the electric street lamps in some

localities they have received the popular name "electric light bugs."

Our largest representatives in the northern United States belong to the

two genera _Belostoma_ and _Banacus_, distinguished from each other by

the fact that _Belostoma_ has a groove on the under side of the femur of

the front leg, for the reception of the tibia.

The salivary glands of Belostoma were figured by Leidy (1847) and later

were studied in more detail by Locy (1884). There are two pairs of the

glands, those of one pair being long and extending back as far as the

beginning of the abdomen, while the others are about one-fourth as long.

They lie on either side of the oesophagus. On each side of the

oesophagus there is a slender tube with a sigmoid swelling which may

serve as a poison reservoir. In addition to this salivary system, there

is a pair of very prominent glands on the ventral side of the head,

opening just above the base of the beak. These Locy has called the

"cephalic glands" and he suggests that they are the source of the

poison. They are the homologues of the maxillary glands described for

other Hemiptera, and it is by no means clear that they are concerned

with the production of venom. It seems more probable that in

_Belostoma_, as in other Hemiptera, it is produced by the salivary

glands, though the question is an open one.

The Belostomatidae feed not only on insects, but on small frogs, fish,

salamanders and the like. Matheson (1907) has recorded the killing of a

good-sized bird by _Belostoma americana_. A woodpecker, or flicker, was

heard to utter cries of distress, and fluttered and fell from a tree. On

examination it was found that a bug of this species had inserted its

beak into the back part of the skull and was apparently busily engaged

in sucking the blood or brains of the bird. Various species of

_Belostoma_ have been cited as causing painful bites in man. We can

testify from personal experience that the bite of _Belostoma americana_

may almost immediately cause severe, shooting pains that may extend

throughout the arm and that they may be felt for several days.

[Illustration: 20. Reduvius (Opsicoetus) personatus. (x2).]

Relief from the pain may be obtained by the use of dilute ammonia, or a

menthol ointment. In the not uncommon case of secondary infection the

usual treatment for that should be adopted.

[Illustration: 21. (_a_) Reduvius personatus, nymph. Photograph by M. V.

S.]

The REDUVIIDAE, or _assassin-bugs_ are capable of inflicting very painful

wounds, as most collectors of Hemiptera know to their sorrow. Some

species are frequently to be found in houses and outhouses and Dr.

Howard suggests that many of the stories of painful spider bites relate

to the attack of these forms.

[Illustration: 21. (_b_) Reduvius personatus, adult (x2) Photograph by

M. V. S.]

An interesting psychological study was afforded in the summer of 1899,

by the "kissing-bug" scare which swept over the country. It was reported

in the daily papers that a new and deadly bug had made its appearance,

which had the unpleasant habit of choosing the lips or cheeks for its

point of attack on man. So widespread were the stories regarding this

supposedly new insect that station entomologists all over the country

began to receive suspected specimens for identification. At Cornell

there were received, among others, specimens of stone-flies, may-flies

and even small moths, with inquiries as to whether they were

"kissing-bugs."

[Illustration: 22. Rasahus biguttatus. (x2). After Howard.]

Dr. L. O. Howard has shown that the scare had its origin in newspaper

reports of some instances of bites by either _Melanolestes picipes_

(fig. 19a) or _Opsicoetes personatus_ (fig. 20), in the vicinity of

Washington, D. C. He then discusses in considerable detail the more

prominent of the Reduviidae which, with greater or less frequency pierce

the skin of human beings. These are _Opsicoetes personatus_,

_Melanolestes picipes_, _Coriscus subcoleoptratus_ (fig. 19_g_),

_Rasahus thoracicus_, _Rasahus biguttatus_ (fig. 22), _Conorhinus

sanguisugus_ (fig. 71), and _Melanolestes abdominalis_ (fig. 23).

[Illustration: 23. Melanolestes abdominalis (x2). After Marlatt.]

One of the most interesting of these species is _Reduvius personatus_,

(= _Opsicoetus personatus_), which is popularly known as the "masked

bed-bug hunter." It owes this name to the fact that the immature nymphs

(fig. 21) have their bodies and legs completely covered by dust and

lint, and that they are supposed to prey upon bed-bugs. LeConte is

quoted by Howard as stating that "This species is remarkable for the

intense pain caused by its bite. I do not know whether it ever willingly

plunges its rostrum into any person, but when caught, or unskilfully

handled it always stings. In this case the pain is almost equal to the

bite of a snake, and the swelling and irritation which result from it

will sometimes last for a week."

A species which very commonly attacks man is _Conorhinus sanguisugus_,

the so-called "big bed-bug" of the south and southern United States. It

is frequently found in houses and is known to inflict an exceedingly

painful bite. As in the case of a number of other predaceous Hemiptera,

the salivary glands of these forms are highly developed. The effect of

the bite on their prey and, as Marlatt has pointed out, the constant and

uniform character of the symptoms in nearly all cases of bites in man,

clearly indicate that their saliva contains a specific substance. No

satisfactory studies of the secretions have been made. On the other

hand, Dr. Howard is doubtless right in maintaining that the very serious

results which sometimes follow the bite are due to the introduction of

extraneous poison germs. This is borne out by the symptoms of most of

the cases cited in literature and also by the fact that treatment with

corrosive sublimate, locally applied to the wound, has yielded favorable

results.

OTHER HEMIPTERA REPORTED AS POISONOUS TO MAN--A large number of other

Hemiptera have been reported as attacking man. Of these, there are

several species of Lygaeidae, Coreidae, and Capsidae. Of the

latter, _Lygus pratensis_, the tarnished plant-bug, is reported by

Professor Crosby as sucking blood. _Orthotylus flavosparsus_ is another

Capsid which has been implicated. _Empoasca mali_ and _Platymetopius

acutus_ of the Jassidae have also been reported as having similar

habits.

Whenever the periodical cicada or "seventeen-year locust" becomes

abundant, the newspapers contain accounts of serious results from its

bites. The senior author has made scores of attempts to induce this

species to bite and only once successfully. At that time the bite was in

no wise more severe than a pin-prick. A student in our department

reports a similar experience. There is no case on record which bears

evidence of being worthy of any credence, whatsoever.

Under the heading of poisonous Hemiptera we might consider the bed-bugs

and the lice. These will be discussed later, as parasites and as

carriers of disease, and therefore need only be mentioned here.

DIPTERA

Several species of blood-sucking Diptera undoubtedly secrete a saliva

possessing poisonous properties. Chief among these are the Culicidae, or

mosquitoes, and the Simuliidae, or black-flies. As we shall consider

these forms in detail under the heading of parasitic species and

insects transmitting disease, we shall discuss here only the poison of

the mosquitoes.

It is well known that mosquitoes, when they bite, inject into the wound

a minute quantity of poison. The effect of this varies according to the

species of mosquito and also depends very much on the susceptibility of

the individual. Soon after the bite a sensation of itching is noticed

and often a wheal, or eminence, is produced on the skin, which may

increase to a considerable swelling. The scratching which is induced may

cause a secondary infection and thus lead to serious results. Some

people seem to acquire an immunity against the poison.

The purpose of this irritating fluid may be, as Reaumur suggested, to

prevent the coagulation of the blood and thus not only to cause it to

flow freely when the insect bites but to prevent its rapid coagulation

in the stomach. Obviously, it is not developed as a protective fluid,

and its presence subjects the group to the additional handicap of the

vengeance of man.

[Illustration: 24. Diagram of a longitudinal section of a mosquito.]

As to the origin of the poison, there has been little question, until

recent years, that it was a secretion from the salivary glands.

Macloskie (1888) showed that each gland is subdivided into three lobes,

the middle of which differs from the others in having evenly granulated

contents and staining more deeply than the others (fig. 24). This middle

lobe he regarded as the source of the poison. Bruck, (1911), by the use

of water, glycerine, chloroform, and other fluids, extracted from the

bodies of a large number of mosquitoes a toxine which he calls

_culicin_. This he assumes comes from the salivary glands. Animal

experimentation showed that this extract possessed hemolytic powers.

Inoculated into the experimenter's own skin it produced lesions which

behaved exactly as do those of mosquito bites.

Similarly, most writers on the subject have concurred with the view that

the salivary glands are the source of the poison. However, recent work,

especially that of Nuttall and Shipley (1903), and Schaudinn (1904), has

shown that the evidence is by no means conclusive. Nuttall dissected out

six sets (thirty-six acini) of glands from freshly killed _Culex

pipiens_ and placed them in a drop of salt solution. The drop was

allowed to dry, it being thought that the salt crystals would facilitate

the grinding up of the glands with the end of a small glass rod, this

being done under microscopic control. After grinding up, a small drop of

water was added of the size of the original drop of saline, and an equal

volume of human blood taken from the clean finger-tip was quickly mixed

therewith, and the whole drawn up into a capillary tube. Clotting was

not prevented and no hemolysis occurred. Salivary gland emulsion added

to a dilute suspension of corpuscles did not lead to hemolysis. This

experiment was repeated a number of times, with slight modification, but

with similar results. The data obtained from the series "do not support

the hypothesis that the salivary glands, at any rate in _Culex pipiens_,

contain a substance which prevents coagulation."

Much more detailed, and the more important experiments made along this

line, are those of Schaudinn (1904). The results of these experiments

were published in connection with a technical paper on the alternation

of generations and of hosts in _Trypanosoma_ and _Spirochaeta_, and for

this reason seem to have largely escaped the notice of entomologists.

They are so suggestive that we shall refer to them in some detail.

Schaudinn observed that the three oesophageal diverticula (commonly,

but incorrectly, known as the "sucking stomach") (fig. 24) usually

contain large bubbles of gas and in addition, he always found yeast

cells. On the ground of numerous observations, Schaudinn was convinced

that these yeast plants are normal and constant commensals of the

insect. He regarded them as the cause of the gas bubbles to be found in

diverticula. It was found that as the insect fed, from time to time the

abdomen underwent convulsive contractions which resulted in the emptying

of the oesophageal diverticula and the salivary glands through blood

pressure.

In order to test the supposed toxic action of the salivary glands,

Schaudinn repeatedly introduced them under his skin and that of his

assistant, in a drop of salt solution, and never obtained a suggestion

of the irritation following a bite of the insect, even though the glands

were carefully rubbed to fragments after their implantation. Like

Nuttall, he failed to get satisfactory evidence that the secretion of

the salivary glands retarded coagulation of the blood.

He then carefully removed the oesophageal diverticula with their

content of yeast and introduced them into an opening in the skin of the

hand. Within a few seconds there was noticeable the characteristic

itching irritation of the mosquito bite; and in a short time there

appeared reddening and typical swelling. This was usually much more

severe than after the usual mosquito bite, and the swelling persisted

and itched longer. This was because by the ordinary bite of the mosquito

most of the yeast cells are again sucked up, while in these experiments

they remained in the wound. These experiments were repeated a number of

times on himself, his assistant and others, and always with the same

result. From them Schaudinn decided that the poisonous action of the

mosquito bite is caused by an enzyme from a commensal fungus. These

conclusions have not, as yet, been satisfactorily tested.

Relief from the effect of the mosquito bite may be obtained by bathing

the swellings with weak ammonia or, according to Howard, by using moist

soap. The latter is to be rubbed gently on the puncture and is said to

speedily allay the irritation. Howard also quotes from the _Journal of

Tropical Medicine and Hygiene_ to the effect that a few drops of a

solution of thirty to forty grains of iodine to an ounce of saponated

petroleum rubbed into the mosquito bite, or wasp sting, allay the pain

instantaneously.

Methods of mosquito control will be discussed later, in considering

these insects as parasites and as carriers of disease.

STINGING INSECTS

The stinging insects all belong to the order HYMENOPTERA. In a number of

families of this group the ovipositor is modified to form a sting and is

connected with poison-secreting glands. We shall consider the apparatus

of the honey-bee and then make briefer reference to that of other forms.

APIS MELLIFICA, THE HONEY BEE--The sting of the worker honey-bee is

situated within a so-called sting chamber at the end of the abdomen.

This chamber is produced by the infolding of the greatly reduced and

modified eighth, ninth and tenth abdominal segments into the seventh.[D]

From it the dart-like sting can be quickly exserted.

The sting (fig. 25) is made up of a central shaft, ventro-laterad of

which are the paired _lancets_, or darts, which are provided with sharp,

recurved teeth. Still further laterad lie the paired whitish,

finger-like _sting palpi_. Comparative morphological as well as

embryological studies have clearly established that these three parts

correspond to the three pairs of gonopophyses of the ovipositor of more

generalized insects.

[Illustration: 25. Sting of a honey bee. _Psn Sc_, base of acid poison

gland; _B Gl_, alkaline poison gland; _Stn Plp_, sting palpi; _Sh B_,

bulb of sting; _Sh A_, basal arm; _Lct_, lancets or darts; _Sh s_, shaft

of sting. Modified from Snodgrass.]

[Illustration: 26. Poison apparatus of a honey bee. Modified from

Snodgrass.]

An examination of the internal structures (fig. 26) reveals two distinct

types of poison glands, the acid-secreting and the alkaline-secreting

glands, and a prominent poison reservoir. In addition, there is a small

pair of accessory structures which have been called lubricating glands,

on account of the supposed function of their product. The acid-secreting

gland empties into the distal end of the poison reservoir which in turn

pours the secretion into the muscular bulb-like enlargement at the base

of the shaft. The alkaline secreting gland empties into the bulb ventrad

of the narrow neck of the reservoir.

The poison is usually referred to as formic acid. That it is not so

easily explained has been repeatedly shown and is evidenced by the

presence of the two types of glands. Carlet maintains that the product

of either gland is in itself innocent,--it is only when they are

combined that the toxic properties appear.

The most detailed study of the poison of the honey-bee is that of Josef

Langer (1897), who in the course of his work used some 25,000 bees.

Various methods of obtaining the active poison for experimental purposes

were used. For obtaining the pure secretion, bees were held in the

fingers and compressed until the sting was exserted, when a clear drop

of the poison was visible at its tip. This was then taken up in a

capillary tube or dilute solutions obtained by dipping the tip of the

sting into a definite amount of distilled water.

An aqueous solution of the poison was more readily obtained by pulling

out the sting and poison sacs by means of forceps, and grinding them up

in water. The somewhat clouded fluid was then filtered one or more

times. For obtaining still greater quantities, advantage was taken of

the fact that while alcohol coagulates the poison, the active principle

remains soluble in water. Hence the stings with the annexed glands where

collected in 96 per cent alcohol, after filtering off of the alcohol

were dried at 40^o C., then rubbed to a fine powder and this was

repeatedly extracted with water. Through filtering of this aqueous

extract there was obtained a yellowish-brown fluid which produced the

typical reactions, according to concentration of the poison.

The freshly expelled drop of poison is limpid, of distinct acid

reaction, tastes bitter and has a delicate aromatic odor. On

evaporation, it leaves a sticky residue, which at 100 degrees becomes

fissured, and suggests dried gum arabic. The poison is readily soluble

in water and possesses a specific gravity of 1.1313. On drying at room

temperature, it leaves a residue of 30 per cent, which has not lost in

poisonous action or in solubility. In spite of extended experiments,

Langer was unable to determine the nature of the active principle. He

showed that it was not, as had been supposed, an albuminous body, but

rather an organic base.

The pure poison, or the two per cent aqueous solution, placed on the

uninjured skin showed absolutely no irritating effect, though it

produced a marked reaction on the mucus membrane of the nose or eye. A

single drop of one-tenth per cent aqueous solution of the poison brought

about a typical irritation in the conjunctiva of the rabbit's eye. On

the other hand, the application of a drop of the poison, or its

solution, to the slightest break in the skin, or by means of a needle

piercing the skin, produced typical effects. There is produced a local

necrosis, in the neighborhood of which there is infiltration of

lymphocytes, oedema, and hyperaemia.

The effect of the sting on man (fig. 27) is usually transitory but there

are some individuals who are made sick for hours, by a single sting.

Much depends, too, on the place struck. It is a common experience that

an angry bee will attempt to reach the eye of its victim and a sting on

the lid may result in severe and prolonged swelling. In the case of a

man stung on the cheek, Legiehn observed complete aphonia and a breaking

out of red blotches all over the body. A sting on the tongue has been

known to cause such collateral oedema as to endanger life through

suffocation. Cases of death of man from the attacks of bees are rare but

are not unknown. Such results are usually from a number of stings but,

rarely, death has been known to follow a single sting, entering a blood

vessel of a particularly susceptible individual.

[Illustration: Effect of bee stings. After Root.]

It is clearly established that partial immunity from the effects of the

poison may be acquired. By repeated injections of the venom, mice have

been rendered capable of bearing doses that certainly would have killed

them at first. It is a well-known fact that most bee-keepers become

gradually hardened to the stings, so that the irritation and the

swelling become less and less. Some individuals have found this immunity

a temporary one, to be reacquired each season. A striking case of

acquired immunity is related by the Roots in their "A B C and X Y Z of

Bee Culture." The evidence in the case is so clear that it should be

made more widely available and hence we quote it here.

A young man who was determined to become a bee-keeper, was so

susceptible to the poison that he was most seriously affected by a

single sting, his body breaking out with red blotches, breathing growing

difficult, and his heart action being painfully accelerated. "We finally

suggested taking a live bee and pressing it on the back of his hand

until it merely pierced his skin with the sting, then immediately

brushing off both bee and sting. This was done and since no serious

effect followed, it was repeated inside of four or five days. This was

continued for some three or four weeks, when the patient began to have a

sort of itching sensation all over his body. The hypodermic injections

of bee-sting poison were then discontinued. At the end of a month they

were repeated at intervals of four or five days. Again, after two or

three weeks the itching sensation came on, but it was less pronounced.

The patient was given a rest of about a month, when the doses were

repeated as before." By this course of treatment the young man became so

thoroughly immunized that neither unpleasant results nor swelling

followed the attacks of the insects and he is able to handle bees with

the same freedom that any experienced bee-keeper does.

In an interesting article in the _Entomological News_ for November,

1914, J. H. Lovell calls attention to the fact that "There has been a

widespread belief among apiarists that a beekeeper will receive more

stings when dressed in black than when wearing white clothing. A large

amount of evidence has been published in the various bee journals

showing beyond question that honey-bees under certain conditions

discriminate against black. A few instances may be cited in

illustration. Of a flock of twelve chickens running in a bee-yard seven

black ones were stung to death, while five light colored ones escaped

uninjured. A white dog ran among the bee-hives without attracting much

attention, while at the same time a black dog was furiously assailed by

the bees. Mr. J. D. Byer, a prominent Canadian beekeeper, relates that a

black and white cow, tethered about forty feet from an apiary, was one

afternoon attacked and badly stung by bees. On examination it was found

that the black spots had five or six stings to one on the white. All

noticed this fact, although no one was able to offer any explanation. A

white horse is in much less danger of being stung, when driven near an

apiary, than a black one. It has, indeed, been observed repeatedly that

domestic animals of all kinds, if wholly or partially black, are much

more liable to be attacked by bees, if they wander among the hives, than

those which are entirely white."

In order to test the matter experimentally, the following series of

experiments was performed. In the language of the investigator:

"On a clear, warm day in August I dressed wholly in white with the

exception of a black veil. Midway on the sleeve of my right arm there

was sewed a band of black cloth ten inches wide. I then entered the

bee-yard and, removing the cover from one of the hives, lifted a piece

of comb with both hands and gently shook it. Instantly many of the bees

flew to the black band, which they continued to attack as long as they

were disturbed. Not a single bee attempted to sting the left sleeve,

which was of course entirely white, and very few even alighted upon it."

"This experiment was repeated a second, third and fourth time; in each

instance with similar results. I estimated the number of bees on the

band of black cloth at various moments was from thirty to forty; it was

evident from their behavior that they were extremely irritable. To the

left white sleeve and other portions of my clothing they paid very

little attention; but the black veil was very frequently attacked."

"A few days later the experiments were repeated, but the band of black

cloth, ten inches wide, was sewed around my left arm instead of around

the right arm as before. When the bees were disturbed, after the hive

cover had been removed, they fiercely attacked the band of black cloth

as in the previous experiences; but the right white sleeve and the white

suit were scarcely noticed. At one time a part of the black cloth was

almost literally covered with furiously stinging bees, and the black

veil was assailed by hundreds. The bees behaved in a similar manner when

a second hive on the opposite side of the apiary was opened."

"A white veil which had been procured for this purpose, was next

substituted for the black veil. The result was most surprising, for,

whereas in the previous experiments hundreds of bees had attacked the

black veil, so few flew against the white veil as to cause me no

inconvenience. Undoubtedly beekeepers will find it greatly to their

advantage to wear white clothing when working among their colonies of

bees and manipulating the frames of the hives."

When a honey-bee stings, the tip of the abdomen, with the entire sting

apparatus, is torn off and remains in the wound. Here the muscles

continue to contract, for some minutes, forcing the barbs deeper and

deeper into the skin, and forcing out additional poison from the

reservoir.

Treatment, therefore, first consists in removing the sting without

squeezing out additional poison. This is accomplished by lifting and

scraping it out with a knife-blade or the fingernail instead of grasping

and pulling it out. Local application of alkalines, such as weak

ammonia, are often recommended on the assumption that the poison is an

acid to be neutralized on this manner, but these are of little or no

avail. They should certainly not be rubbed in, as that would only

accelerate the absorption of the poison. The use of cloths wrung out in

hot water and applied as hot as can be borne, affords much relief in the

case of severe stings. The application of wet clay, or of the end of a

freshly cut potato is sometimes helpful.

In extreme cases, where there is great susceptibility, or where there

may have been many stings, a physician should be called. He may find

strychnine injections or other treatment necessary, if general symptoms

develop.

[Illustration: 28. The poison apparatus of Formica. Wheeler, after

Forel.]

OTHER STINGING FORMS--Of the five thousand, or more, species of bees,

most possess a sting and poison apparatus and some of the larger forms

are capable of inflicting a much more painful sting than that of the

common honey-bee. In fact, some, like the bumble bees, possess the

advantage that they do not lose the sting from once using it, but are

capable of driving it in repeatedly. In the tropics there are found many

species of stingless bees but these are noted for their united efforts

to drive away intruders by biting. Certain species possess a very

irritating saliva which they inject into the wounds.

The ants are not ordinarily regarded as worthy of consideration under

the heading of "stinging insects" but as a matter of fact, most of them

possess well developed stings and some of them, especially in the

tropics, are very justly feared. Even those which lack the sting possess

well-developed poison glands and the parts of the entire stinging

apparatus, in so far as it is developed in the various species, may

readily be homologized with those of the honey-bee.

The ants lacking a sting are those of the subfamily CAMPONOTINAE, which

includes the largest of our local species. It is an interesting fact

that some of these species possess the largest poison glands and

reservoir (fig. 28) and it is found that when they attack an enemy they

bring the tip of the abdomen forward and spray the poison in such a way

that it is introduced into the wound made by the powerful mandibles.

[Illustration: 29. A harmless, but much feared larva, the "tomato worm."

Natural size. Photograph by M. V. S.]

More feared than any of the other Hymenoptera are the hornets and wasps.

Of these there are many species, some of which attain a large size and

are truly formidable. Phisalix (1897), has made a study of the venom of

the common hornet and finds that, like the poison of the honey-bee, it

is neither an albuminoid nor an alkaloid. Its toxic properties are

destroyed at 120^o C. Phisalix also says that the venom is soluble in

alcohol. If this be true, it differs in this respect from that of the

bee. An interesting phase of the work of Phisalix is that several of her

experiments go to show that the venom of hornets acts as a vaccine

against that of vipers.

NETTLING INSECTS

So far, we have considered insects which possess poison glands connected

with the mouth-parts or a special sting and which actively inject their

poison into man. There remain to be considered those insects which

possess poisonous hairs or body fluids which, under favorable

circumstances, may act as poisons. To the first of these belong

primarily the larvae of certain Lepidoptera.

LEPIDOPTERA

[Illustration: 30. Another innocent but much maligned caterpillar, the

larva of the Regal moth. Photograph by M. V. S.]

When we consider the reputedly poisonous larvae of moths and butterflies,

one of the first things to impress us is that we cannot judge by mere

appearance. Various species of Sphingid, or hawk-moth larvae, bear at the

end of the body a chitinous horn, which is often referred to as a

"sting" and regarded as capable of inflicting dangerous wounds. It would

seem unnecessary to refer to this absurd belief if it were not that each

summer the newspapers contain supposed accounts of injury from the

"tomato worm" (fig. 29) and others of this group. The grotesque, spiny

larva (fig. 30) of one of our largest moths, _Citheronia regalis_ is

much feared though perfectly harmless, and similar instances could be

multiplied.

[Illustration: 31. The flannel moth (Lagoa crispata). (_a_) Poisonous

larva.]

[Illustration: 31. (_b_) Adult. Enlarged. Photographs by M. V. S.]

But if the larvae are often misjudged on account of their ferocious

appearance, the reverse may be true. A group of most innocent looking

and attractive caterpillars is that of the flannel-moth larvae, of which

_Lagoa crispata_ may be taken as an example. Its larva (fig. 31) has a

very short and thick body, which is fleshy and completely covered and

hidden by long silken hairs of a tawny or brown color, giving a convex

form to the upper side. Interspersed among these long hairs are

numerous short spines connected with underlying hypodermal poison

glands. These hairs are capable of producing a marked nettling effect

when they come in contact with the skin. This species is found in our

Atlantic and Southern States. Satisfactory studies of its poisonous

hairs and their glands have not yet been made.

[Illustration: 32 The poisonous saddle back caterpillar. Empretia

(Sibine) stimulea. Photograph by M. V. S.]

[Illustration: 33_a_. Io moth larvae on willow. Photograph by M. V. S.]

_Sibine stimulea (Empretia stimulea)_, or the saddle-back caterpillar

(fig. 32), is another which possesses nettling hairs. This species

belongs to the group of Eucleidae, or slug caterpillars. It can be

readily recognized by its flattened form, lateral, bristling spines and

by the large green patch on the back resembling a saddle-cloth, while

the saddle is represented by an oval, purplish-brown spot. The small

spines are venomous and affect some persons very painfully. The larva

feeds on the leaves of a large variety of forest trees and also on

cherry, plum, and even corn leaves. It is to be found throughout the

Eastern and Southern United States.

[Illustration: 33_b_. Io moth. Full grown larva. Photograph by M. V. S.]

[Illustration: 34. Io moth. Adult. Photograph by M. V. S.]

_Automeris io_ is the best known of the nettling caterpillars. It is the

larva of the Io moth, one of the Saturniidae. The mature caterpillar,

(fig. 33), which reaches a length of two and one-half inches, is of a

beautiful pale green with sublateral stripes of cream and red color and

a few black spines among the green ones. The green radiating spines give

the body a mossy appearance. They are tipped with a slender chitinous

hair whose tip is readily broken off in the skin and whose poisonous

content causes great irritation. Some individuals are very susceptible

to the poison, while others are able to handle the larvae freely without

any discomfort. The larvae feed on a wide range of food plants. They are

most commonly encountered on corn and on willow, because of the

opportunities for coming in contact with them.

[Illustration: 35. Larva of brown-tail moth. (Natural size). Photograph

by M. V. S.]

The larvae of the brown-tail moth (_Euproctis chrysorrhoea_) (fig. 35

and 36), where they occur in this country, are, on account of their

great numbers, the most serious of all poisonous caterpillars. It is not

necessary here, to go into details regarding the introduction of this

species from Europe into the New England States. This is all available

in the literature from the United States Bureau of Entomology and from

that of the various states which are fighting the species. Suffice to

say, there is every prospect that the pest will continue to spread

throughout the Eastern United States and Canada and that wherever it

goes it will prove a direct pest to man as well as to his plants.

Very soon after the introduction of the species there occurred in the

region where it had gained a foothold, a mysterious dermatitis of man.

The breaking out which usually occurred on the neck or other exposed

part of the body was always accompanied by an intense itching. It was

soon found that this dermatitis was caused by certain short, barbed

hairs of the brown-tail caterpillars and that not only the caterpillars

but their cocoons and even the adult female moths might harbor these

nettling hairs and thus give rise to the irritation. In many cases the

hairs were wafted to clothing on the line and when this was worn it

might cause the same trouble. Still worse, it was found that very

serious internal injury was often caused by breathing or swallowing the

poisonous hairs.

[Illustration: 36. Browntail moths. One male and two females. Photograph

by M. V. S.]

The earlier studies seemed to indicate that the irritation was purely

mechanical in origin, the result of the minute barbed hairs working into

the skin in large numbers. Subsequently, however, Dr. Tyzzer (1907)

demonstrated beyond question that the trouble was due to a poison

contained in the hairs. In the first place, it is only the peculiar

short barbed hairs which will produce the dermatitis when rubbed on the

skin, although most of the other hairs are sharply barbed. Moreover, it

was found that in various ways the nettling properties could be

destroyed without modifying the structure of the hairs. This was

accomplished by baking for one hour at 110^o C, by warming to 60^o C in

distilled water, or by soaking in one per cent. or in one-tenth per

cent. of potassium hydrate or sodium hydrate. The most significant part

of his work was the demonstration of the fact that if the nettling

hairs are mingled with blood, they immediately produce a change in the

red corpuscles. These at once become coarsely crenated, and the roleaux

are broken up in the vicinity of the hair (fig. 37_b_). The corpuscles

decrease in size, the coarse crenations are transformed into slender

spines which rapidly disappear, leaving the corpuscles in the form of

spheres, the light refraction of which contrasts them sharply with the

normal corpuscles. The reaction always begins at the basal sharp point

of the hair. It could not be produced by purely mechanical means, such

as the mingling of minute particles of glass wool, the barbed hairs of a

tussock moth, or the other coarser hairs of the brown-tail, with the

blood.

[Illustration: 37. (_a_) Ordinary hairs and three poison hairs of

subdorsal and lateral tubercles of the larva of the browntail moth.

Drawing by Miss Kephart.]

The question of the source of the poison has been studied in our

laboratory by Miss Cornelia Kephart. She first confirmed Dr. Tyzzer's

general results and then studied carefully fixed specimens of the larvae

to determine the distribution of the hairs and their relation to the

underlying tissues.

[Illustration: 37. (_b_) Effect of the poison on the blood corpuscles of

man. After Tyzzer.]

The poison hairs (fig. 37), are found on the subdorsal and lateral

tubercles (fig. 38), in bunches of from three to twelve on the minute

papillae with which the tubercles are thickly covered. The underlying

hypodermis is very greatly thickened, the cells being three or four

times the length of the ordinary hypodermal cells and being closely

crowded together. Instead of a pore canal through the cuticula for each

individual hair, there is a single pore for each papillae on a tubercle,

all the hairs of the papilla being connected with the underlying cells

through the same pore canal, (figs. 39 and 40).

[Illustration: 38. Cross section of the larva of the browntail moth

showing the tubercles bearing the poison hairs. Drawing by Miss

Kephart.]

The hypodermis of this region is of two distinct types of cells. First,

there is a group of slender fusiform cells, one for each poison hair on

the papilla, which are the trichogen, or hair-formative cells. They are

crowded to one side and towards the basement membrane by a series of

much larger, and more prominent cells (fig. 40), of which there is a

single one for each papilla. These larger cells have a granular

protoplasm with large nuclei and are obviously actively secreting. They

are so characteristic in appearance as to leave no question but that

they are the true poison glands.

[Illustration: 39. Epithelium underlying poison hairs of the larva of

the browntail moth. Drawing by Miss Kephart.]

Poisonous larvae of many other species have been reported from Europe and

especially from the tropics but the above-mentioned species are the more

important of those occurring in the United States and will serve as

types. It should be noted in this connection that through some curious

misunderstanding Goeldi (1913) has featured the larva of _Orgyia

leucostigma_, the white-marked tussock moth, as the most important of

the poisonous caterpillars of this country. Though there are occasional

reports of irritation from its hairs such cases are rare and there is no

evidence that there is any poison present. Indeed, subcutaneous

implantation of the hairs leads to no poisoning, but merely to temporary

irritation.

[Illustration: 40. Same as figure 39, on larger scale.]

Occasionally, the hairs of certain species of caterpillars find

lodgement in the conjunctiva, cornea, or iris of the eye of man and give

rise to the condition known as _opthalmia nodosa_. The essential feature

of this trouble is a nodular conjunctivitis which simulates tuberculosis

of the conjunctiva and hence has been called _pseudo-tubercular_. It may

be distinguished microscopically by the presence of the hairs.

[Illustration: 41. (_a_) Nodular conjunctivitis in the eye of a child.

De Schweinitz and Shumway.]

Numerous cases of opthalmia nodosa are on record. Of those from this

country, one of the most interesting is reported by de Schweinitz and

Shumway (1904). It is that of a child of fifteen years whose eye had

become inflamed owing to the presence of some foreign body. Downward and

inward on the bulbar conjunctiva were a number of flattened,

grayish-yellow nodules, between which was a marked congestion of the

conjunctival and episcleral vessels (fig. 41_a_). Twenty-seven nodules

could be differentiated, those directly in the center of the collection

being somewhat confluent and assuming a crescentic and circular

appearance. The nodules were excised and, on sectioning, were found to

be composed of a layer of spindle cells and round cells, outside of

which the tissue was condensed into a capsule. The interior consisted of

epithelioid cells, between which was a considerable intercellular

substance. Directly in the center of a certain number of nodules was

found the section of a hair (fig. 41_b_). The evidence indicated that

the injury had resulted from playing with caterpillars of one of the

Arctiid moths, _Spilosoma virginica_. Other reported cases have been

caused by the hairs of larvae of _Lasiocampa rubi_, _L. pini_,

_Porthetria dispar_, _Psilura monacha_ and _Cnethocampa processionea_.

[Illustration: 41_b_. Section through one of the nodules showing the

caterpillar hair. De Schweinitz and Shumway.]

RELIEF FROM POISONING BY NETTLING LARVAE--The irritation from nettling

larvae is often severe and, especially in regions where the brown-tail

abounds, inquiries as to treatment arise. In general, it may be said

that cooling lotions afford relief, and that scratching, with the

possibilities of secondary infection, should be avoided, in so far as

possible.

Among the remedies usually at hand, weak solutions of ammonia, or a

paste of ordinary baking soda are helpful. Castellani and Chalmers

recommend cleaning away the hairs by bathing the region with an alkaline

lotion, such as two per cent solution of bicarbonate of soda, and then

applying an ointment of ichthyol (10%).

In the brown-tail district, there are many proprietary remedies of which

the best ones are essentially the following, as recommended by Kirkland

(1907):

Carbolic acid 1/2 drachm.

Zinc oxide 1/2 oz.

Lime water 8 oz.

Shake thoroughly and rub well into the affected parts.

In some cases, and especially where there is danger of secondary

infection, the use of a weak solution of creoline (one teaspoonful to a

quart of water), is to be advised.

VESCICATING INSECTS AND THOSE POSSESSING OTHER POISONS IN THEIR BLOOD

PLASMA

We have seen that certain forms, for example, the poisonous spiders, not

only secrete a toxine in their poison glands, but that such a substance

may be extracted from other parts of their body, or even their eggs.

There are many insects which likewise possess a poisonous blood plasma.

Such forms have been well designated by Taschenberg as _cryptotoxic_

([Greek: kryptos] = hidden). We shall consider a few representative

forms.

[Illustration: 42_a_. Blister beetle.]

[Illustration: 42_b_. An American blister beetle. Meloe angusticollis.

Photograph by M. V. S.]

THE BLISTER BEETLES--Foremost among the cryptotoxic insects are the

_Meloidae_ or "blister beetles," to which the well-known "Spanish fly"

(fig. 42_a_), formerly very generally used in medical practice, belongs.

The vescicating property is due to the presence in the blood plasma of a

peculiar, volatile, crystalline substance known as _cantharidin_, which

is especially abundant in the reproductive organs of the beetle.

According to Kobert, the amount of this varies in different species from

.4 or .5% to 2.57% of the dry weight of the beetle.

While blister beetles have been especially used for external

application, they are also at times used internally as a stimulant and a

diuretic. The powder or extract was formerly much in vogue as an

aphrodisiac, and formed the essential constituent of various philters,

or "love powders". It is now known that its effects on the reproductive

organs appear primarily after the kidneys have been affected to such an

extent as to endanger life, and that many cases of fatal poison have

been due to its ignorant use.

There are many cases on record of poisoning and death due to internal

use, and in some instances from merely external application. There are

not rarely cases of poisoning of cattle from feeding on herbage bearing

a large number of the beetles and authentic cases are known of human

beings who have been poisoned by eating the flesh of such cattle. Kobert

states that the beetles are not poisonous to birds but that the flesh of

birds which have fed on them is poisonous to man, and that if the flesh

of chickens or frogs which have fed on the cantharidin be fed to cats it

causes in them the same symptoms as does the cantharidin.

Treatment of cases of cantharidin poison is a matter for a skilled

physician. Until he can be obtained, emetics should be administered and

these should be followed by white of egg in water. Oils should be

avoided, as they hasten the absorption of the poison.

OTHER CRYPTOTOXIC INSECTS--Though the blister beetles are the best known

of the insects with poisonous blood plasma, various others have been

reported and we shall refer to a few of the best authenticated.

One of the most famous is the Chrysomelid beetle, _Diamphidia simplex_,

the body fluids of whose larvae are used by certain South African bushmen

as an arrow poison. Its action is due to the presence of a toxalbumin

which exerts a haemolytic action on the blood, and produces inflammation

of the subcutaneous connective tissue and mucous membranes. Death

results from general paralysis. Krause (1907) has surmised that the

active principle may be a bacterial toxin arising from decomposition of

the tissues of the larva, but he presents no support of this view and it

is opposed by all the available evidence.

In China, a bug, _Heuchis sanguinea_, belonging to the family Cicadidae,

is used like the Meloidae, to produce blistering, and often causes

poisoning. It has been assumed that its vescicating properties are due

to cantharidin, but the presence of this substance has not been

demonstrated.

Certain Aphididae contain a strongly irritating substance which produces,

not merely on mucous membranes but on outer skin, a characteristic

inflammation.

It has been frequently reported that the larvae of the European cabbage

butterfly, _Pieris brassicae_, accidentally eaten by cows, horses, ducks,

and other domestic animals, cause severe colic, attempts to vomit,

paralysis of the hind legs, salivation, and stomatitis. On _postmortem_

there are to be found haemorrhagic gastro-enteritis, splenitis, and

nephritis. Kobert has recently investigated the subject and has found a

poisonous substance in the blood of not only the larvae but also the

pupae.

FOOTNOTES:

[A] This is diametrically opposed to the findings of Bordas (1905) in

the case of the European _Latrodectus 13-guttatus_, whose glands are

"much larger than those of other spiders." From a considerable

comparative study, we should also unhesitatingly make this statement

regarding the glands of our American species, _L. mactans_.

[B] Dr. E. H. Coleman (Kellogg, 1915) has demonstrated its virulence by

a series of experiments comparable with those of Kobert.

[C] According to Stiles, the species occurring in the Northwest which is

commonly identified as _D. venustus_ should be called _D. andersoni_

(see footnote, chapter 12).

[D] It should be remembered that in all the higher Hymenoptera the first

abdominal segment is fused with the thorax and that what is apparently

the sixth segment is, in reality, the seventh.

CHAPTER III

PARASITIC ARTHROPODA AFFECTING MAN

The relation of insects to man as simple parasites has long been

studied, and until very recent years the bulk of the literature of

medical entomology referred to this phase of the subject. This is now

completely overshadowed by the fact that so many of these parasitic

forms are more than simple parasites, they are transmitters of other

microscopic parasites which are pathogenic to man. Yet the importance of

insects as parasites still remains and must be considered in a

discussion of the relation of insects to the health of man. In taking up

the subject we shall first consider some general features of the

phenomenon of animal parasitism.

Parasitism is an adaptation which has originated very often among living

organisms and in widely separated groups. It would seem simple to define

what is meant by a "parasite" but, in reality, the term is not easily

limited. It is often stated that a parasite is "An organism which lives

at the expense of another," but this definition is applicable to a

predatory species or, in its broadest sense, to all organisms. For our

purpose we may say with Braun: "A parasite is an organism which, for the

purpose of obtaining food, takes up its abode, temporarily or

permanently, on or within another living organism".

Thus, parasitism is a phase of the broad biological phenomenon of

_symbiosis_, or living together of organisms. It is distinguished from

_mutualism_, or symbiosis in the narrow sense, by the fact that only one

party to the arrangement obtains any advantage, while the other is to a

greater or less extent injured.

Of parasites we may distinguish on the basis of their location on or in

the host, _ecto-parasites_, which live outside of the body; and

_endo-parasites_, which live within the body. On account of their method

of breathing the parasitic arthropods belong almost exclusively to the

first of these groups.

On the basis of relation to their host, we find _temporary parasites_,

those which seek the host only occasionally, to obtain food; and the

_stationary_ or _permanent_ parasites which, at least during certain

stages, do not leave their host.

_Facultative parasites_ are forms which are not normally parasitic, but

which, when accidentally ingested, or otherwise brought into the body,

are able to exist for a greater or less period of time in their unusual

environment. These are generally called in the medical literature

"pseudoparasites" but the term is an unfortunate one.

We shall now take up the different groups of arthropods, discussing the

more important of the parasitic forms attacking man. The systematic

relationship of these forms, and key for determining important species

will be found in Chapter XII.

ACARINA OR MITES

The ACARINA, or _mites_, form a fairly natural group of arachnids,

characterized, in general, by a sac-like, unsegmented body which is

generally fused with the cephalothorax. The mouth-parts have been united

to form a beak or rostrum.

The representatives of this group undergo a marked metamorphosis.

Commonly, the larvae on hatching from the egg, possess but three pairs of

legs, and hence are called _hexapod larvae_. After a molt, they transform

into nymphs which, like the adult, have four pairs of legs and are

called _octopod nymphs_. These after a period of growth, molt one or

more times and, acquiring external sexual organs, become adult.

Most of the mites are free-living, but there are many parasitic species

and as these have originated in widely separated families, the Acarina

form an especially favorable group for study of the origin of

parasitism. Such a study has been made by Ewing (1911), who has reached

the following conclusions:

"We have strong evidence indicating that the parasitic habit has

originated independently at least eleven times in the phylogeny of the

Ararina. Among the zoophagous parasites, the parasitic habit has been

developed from three different types of free-living Acarina: (a)

predaceous forms, (b) scavengers, (c) forms living upon the juices of

plants."

Ewing also showed that among the living forms of Acarina we can trace

out all the stages of advancing parasitism, semiparasitism, facultative

parasitism, even to the fixed and permanent type, and finally to

endoparasitism.

Of the many parasitic forms, there are several species which are serious

parasites of man and we shall consider the more important of these.

Infestation by mites is technically known as _acariasis_.

[Illustration: 43. Effect of the harvest mites on the skin of man.

Photograph by J. C. Bradley.]

The Trombidiidae, or Harvest Mites

In many parts of this country it is impossible for a visitor to go into

the fields and, particularly, into berry patches and among tall weeds

and grass in the summer or early fall without being affected by an

intolerable itching, which is followed, later, by a breaking out of

wheals, or papules, surrounded by a bright red or violaceous aureola,

(fig. 43). It is often regarded as a urticaria or eczema, produced by

change of climate, an error in diet, or some condition of general

health.

Sooner or later, the victim finds that it is due to none of these, but

to the attacks of an almost microscopic red mite, usually called

"jigger" or "chigger" in this country. As the term "chigger" is applied

to one of the true fleas, _Dermatophilus penetrans_, of the tropics,

these forms are more correctly known as "harvest mites." Natives of an

infested region may be so immune or accustomed to its attacks as to be

unaware of its presence, though such immunity is by no means possessed

by all who have been long exposed to the annoyance.

[Illustration: 44. Harvest mites. (Larvae of Trombidium). After C. V.

Riley.]

The harvest mites, or chiggers, attacking man are larval forms,

possessing three pairs of legs (fig. 44). Their systematic position was

at first unknown and they were classed under a special genus _Leptus_, a

name which is very commonly still retained in the medical literature. It

is now known that they are the larval forms of various species of the

genus _Trombidium_, a group of predaceous forms, the adults of which

feed primarily on insects and their eggs. In this country the species

best known are those to be found late in summer, as larvae at the base of

the wings of houseflies or grasshoppers.

There is much uncertainty as to the species of the larvae attacking man

but it is clear that several are implicated. Bruyant has shown that in

France the larvae _Trombidium inapinatum_ and _Trombidium holosericeum_

are those most frequently found. The habit of attacking man is abnormal

and the larvae die after entering the skin. Normally they are parasitic

on various insects.

Most recent writers agree that, on man, they do not bore into the skin,

as is generally supposed, but enter a hair follicle or sebaceous gland

and from the bottom of this, pierce the cutis with their elongate

hypopharynx. According to Braun, there arises about the inserted

hypopharynx a fibrous secretion--the so-called "beak" which is, in

reality, a product of the host. Dr. J. C. Bradley, however, has made

careful observations on their method of attack, and he assures us that

the mite ordinarily remains for a long time feeding on the surface of

the skin, where it produces the erythema above described. During this

time it is not buried in the skin but is able to retreat rapidly into it

through a hair follicle or sweat gland. The irritation from the mites

ceases after a few days, but not infrequently the intolerable itching

leads to so much scratching that secondary infection follows.

Relief from the irritation may be afforded by taking a warm salt bath as

soon as possible after exposure or by killing the mites by application

of benzine, sulphur ointment or carbolized vaseline. When they are few

in number, they can be picked out with a sterile needle.

Much may be done in the way of warding off their attacks by wearing

gaiters or close-woven stockings extending from ankle to the knee. Still

more efficacious is the sprinkling of flowers of sulphur in the

stockings and the underclothes from a little above the knee, down. The

writers have known this to make it possible for persons who were

especially susceptible to work with perfect comfort in badly infested

regions. Powdered naphthalene is successfully used in the same way and

as Chittenden (1906) points out, is a safeguard against various forms of

man-infesting tropical insect pests.

The question of the destruction of the mites in the field is sometimes

an important one, and under some conditions, is feasible. Chittenden

states that much can be accomplished by keeping the grass, weeds, and

useless herbage mowed closely, so as to expose the mites to the sun. He

believes that in some cases good may be done by dusting the grass and

other plants, after cutting, with flowers of sulphur or by spraying with

dilute kerosene emulsion in which sulphur has been mixed. More recently

(1914) he calls attention to the value of cattle, and more especially

sheep, in destroying the pests by tramping on them and by keeping the

grass and herbage closely cropped.

IXODOIDEA OR TICKS

Until recently, the ticks attracted comparatively little attention from

entomologists. Since their importance as carriers of disease has been

established, interest in the group has been enormously stimulated and

now they rank second only to the mosquitoes in the amount of detailed

study that has been devoted to them.

[Illustration: 45_a_. Argus persicus. Capitulum of male. After Nuttall

and Warburton.]

The ticks are the largest of the Acarina. They are characterized by the

fact that the hypostome, or "tongue" (fig. 45) is large and file-like,

roughened by sharp teeth. They possess a breathing pore on each side of

the body, above the third or fourth coxae (fig. 45_b_).

[Illustration: 45_b_. Left spiracle of nymph of _Argas persicus_. After

Nuttall and Warburton.]

There are two distinct families of the IXODOIDEA, differing greatly in

structure, life-history and habits. These are the ARGASIDAE and the

IXODIDAE. We shall follow Nuttall (1908) in characterizing these two

families and in pointing out their biological differences, and shall

discuss briefly the more important species which attack man. The

consideration of the ticks as carriers of disease will be reserved for a

later chapter.

Argasidae

In the ticks belonging to the family ARGASIDAE, there is comparatively

little sexual dimorphism, while this is very marked in the Ixodidae. The

capitulum, or so-called "head" is ventral, instead of terminal; the

palpi are leg-like, with the segments subequal; the scutum, or dorsal

shield, is absent; eyes, when present, are lateral, on supracoxal folds.

The spiracles are very small; coxae unarmed; tarsi without ventral

spurs, and the pulvilli are absent or rudimentary.

In habits and life history the Argasidae present striking

characteristics. In the first place, they are long-lived, a factor which

counts for much in the maintenance of the species. They are intermittent

feeders, being comparable with the bed-bug in this respect. There are

two or more nymphal stages, and they may molt after attaining maturity.

The female lays comparatively few eggs in several small batches.

Nuttall (1911) concludes that "The Argasidae represent the relatively

primitive type of ticks because they are less constantly parasitic than

are the Ixodidae. Their nymphs and adults are rapid feeders and chiefly

infest the habitat of their hosts. * * * Owing to the Argasidae infesting

the habitats of their hosts, their resistance to prolonged starvation

and their rapid feeding habits, they do not need to bring forth a large

progeny, because there is less loss of life in the various stages, as

compared with the Ixodidae, prior to their attaining maturity."

[Illustration: 46. Argus persicus. Dorsal and ventral aspects. (x4).

After Hassell.]

Of the Argasidae, we have in the United States, several species which

have been reported as attacking man.

_Argas persicus_, the famous "Miana bug" (fig. 46), is a very widely

distributed species, being reported from Europe, Asia, Africa, and

Australia. It is everywhere preeminently a parasite of fowls. According

to Nuttall it is specifically identical with _Argas americanus_ Packard

or _Argas miniatus_ Koch, which is commonly found on fowls in the United

States, in the South and Southwest. Its habits are comparable to those

of the bed-bug. It feeds intermittently, primarily at night, and instead

of remaining on its host, it then retreats to cracks and crevices.

Hunter and Hooker (1908) record that they have found the larva to remain

attached for five or eight days before dropping. Unlike the Ixodidae, the

adults oviposit frequently.

[Illustration: 47. Otiobius (Ornithodoros) megnini, head of nymph. After

Stiles.]

[Illustration: 48. Otiobius (Ornithodoros) megnini, male. (_a_) dorsal,

(_b_) ventral aspect. After Nuttall and Warburton.]

The most remarkable feature of the biology of this species is the great

longevity, especially of the adult. Hunter and Hooker report keeping

larvae confined in summer in pill boxes immediately after hatching for

about two months while under similar conditions those of the Ixodid,

_Boophilus annulatus_ lived for but two or three days. Many writers have

recorded keeping adults for long periods without food. We have kept

specimens in a tin box for over a year and a half and at the end of that

time a number were still alive. Laboulliene kept unfed adults for over

three years. In view of the effectiveness of sulphur in warding off the

attacks of Trombidiidae, it is astonishing to find that Lounsbury has

kept adults of _Argas persicus_ for three months in a box nearly filled

with flowers of sulphur, with no apparent effect on them.

We have already called attention to the occasional serious effects of

the bites of this species. While such reports have been frequently

discredited there can be no doubt that they have foundation in fact. The

readiness with which this tick attacks man, and the extent to which old

huts may be infested makes it especially troublesome.

_Otiobius (Ornithodoros) megnini_, the "spinose ear-tick" (figs. 47,

48), first described from Mexico, as occurring in the ears of horses, is

a common species in our Southwestern States and is recorded by Banks as

occurring as far north as Iowa.

The species is remarkable for the great difference between the spiny

nymph stage and the adult. The life history has been worked out by

Hooker (1908). Seed ticks, having gained entrance to the ear, attach

deeply down in the folds, engorge, and in about five days, molt; as

nymphs with their spinose body they appear entirely unlike the larvae. As

nymphs they continue feeding sometimes for months. Finally the nymph

leaves the host, molts to form the unspined adult, and without further

feeding is fertilized and commences oviposition.

The common name is due to the fact that in the young stage the ticks

occur in the ear of their hosts, usually horses or cattle. Not

uncommonly it has been reported as occurring in the ear of man and

causing very severe pain. Stiles recommends that it be removed by

pouring some bland oil into the ear.

Banks (1908) reports three species of _Ornithodoros_--_O. turicata_,

_coriaceus_ and _talaje_--as occurring in the United States. All of these

attack man and are capable of inflicting very painful bites.

Ixodidae

The ticks belonging to the family IXODIDAE (figs. 49 and 50) exhibit a

marked sexual dimorphism. The capitulum is anterior, terminal, instead

of ventral as in the Argasidae; the palpi are relatively rigid (except in

the subfamily Ixodinae), with rudimentary fourth segment; scutum present;

eyes, when present, dorsal, on side of scutum. The spiracles are

generally large, situated well behind the fourth coxae; coxae generally

with spurs; pulvilli always present.

In habits and life history the typical Ixodidae differ greatly from

the Argasidae. They are relatively short-lived, though some recent

work indicates that their longevity has been considerably

under-estimated. Typically, they are permanent feeders, remaining on the

host, or hosts, during the greater part of their life. They molt twice

only, on leaving the larval and the nymphal stages. The adult female

deposits a single, large batch of eggs. Contrasting the habits of the

Ixodidae to those of the Argasidae, Nuttall (1911) emphasizes that

the Ixodidae are more highly specialized parasites. "The majority are

parasitic on hosts having no fixed habitat and consequently all stages,

as a rule, occur upon the host."

[Illustration: 49. Ixodes ricinus; male, ventral aspect. After Braun and

Luehe.]

As mere parasites of man, apart from their power to transmit disease,

the Ixodidae are much less important than the Argasidae. Many are

reported as occasionally attacking man and of these the following native

species may be mentioned.

[Illustration: 50. Ixodes ricinus, var. scapularis, female. Capitulum

and scutum; ventral aspect of capitulum; coxae; tarsus 4; spiracle;

genital and anal grooves. After Nuttall and Warburton.]

_Ixodes ricinus_, the European castor bean tick (figs. 49, 50), is a

species which has been often reported from this country but Banks (1908)

has shown that, though it does occur, practically all of the records

apply to _Ixodes scapularis_ or _Ixodes cookei_. In Europe, _Ixodes

ricinus_ is very abundant and very commonly attacks man. At the point

of penetration of the hypostome there is more or less inflammation but

serious injury does not occur unless there have been introduced

pathogenic bacteria or, unless the tick has been abruptly removed,

leaving the capitulum in the wound. Under the latter circumstances,

there may be an abscess formed about the foreign body and occasionally,

serious results have followed. Under certain conditions the tick, in

various stages, may penetrate under the skin and produce a tumor, within

which it may survive for a considerable period of time.

_Ixodes cookei_ is given by Banks as "common on mammals in the Eastern

States as far west as the Rockies." It is said to affect man severely.

_Amblyomma americanum_, (fig. 158c), the "lone star tick," is widely

distributed in the United States. Its common name is derived from the

single silvery spot on the scutum of the female. Hunter and Hooker

regard this species as, next to _Boophilus annulatus_, the most

important tick in the United States. Though more common on cattle, it

appears to attack mammals generally, and "in portions of Louisiana and

Texas it becomes a pest of considerable importance to moss gatherers and

other persons who spend much time in the forests."

_Amblyomma cajennense_, noted as a pest of man in central and tropical

America, is reported from various places in the south and southwestern

United States.

_Dermacentor variabilis_ is a common dog tick of the eastern United

States. It frequently attacks man, but the direct effects of its bite

are negligible.

The "Rocky Mountain spotted fever tick" (_Dermacentor andersoni_

according to Stiles, _D. venustus_ according to Banks) is, from the

viewpoint of its effects on man, the most important of the ticks of the

United States. This is because, as has been clearly established, it

transmits the so-called "spotted fever" of man in our northwestern

states. This phase of the subject will be discussed later and it need

merely be mentioned here, that this species has been reported as causing

painful injuries by its bites. Dr. Stiles states that he has seen cases

of rather severe lymphangitis and various sores and swellings developing

from this cause. In one case, of an individual bitten near the elbow,

the arm became very much swollen and the patient was confined in bed for

several days. The so-called tick paralysis produced by this species is

discussed in a preceding chapter.

There are many other records of various species of ticks attacking man,

but the above-mentioned will serve as typical and it is not necessary to

enter into greater detail.

TREATMENT OF TICK BITES--When a tick attaches to man the first thing to

be done is to remove it without leaving the hypostome in the wound to

fester and bring about secondary effects. This is best accomplished by

applying to the tick's body some substance which will cause it to more

readily loosen its hold. Gasoline or petroleum, oil or vaseline will

serve. For removing the spinose ear-tick, Stiles recommends pouring some

bland oil into the ear. Others have used effectively a pledget of cotton

soaked in chloroform.

In general, the treatment recommended by Wellman for the bites of

_Ornithodoros moubata_ will prove helpful. It consists of prolonged

bathing in very hot water, followed by the application of a strong

solution of bicarbonate of soda, which is allowed to dry upon the skin.

He states that this treatment is comforting. For severe itching he

advises smearing the bites with vaseline, which is slightly impregnated

with camphor or menthol. Medical aid should be sought when complications

arise.

The DERMANYSSIDAE are Gamasid mites which differ from others of the group

in that they are parasitic on vertebrates. None of the species normally

attack man, but certain of them, especially the poultry mite, may be

accidental annoyances.

[Illustration: 51. Dermanyssus gallinae, female. After Delafond.]

_Dermanyssus gallinae_ (fig. 51), the red mite of poultry, is an

exceedingly common and widespread parasite of fowls. During the day it

lives in cracks and crevices of poultry houses, under supports of

roosts, and in litter of the food and nests, coming out at night to

feed. They often attack people working in poultry houses or handling

and plucking infested fowls. They may cause an intense pruritis, but

they do not produce a true dermatosis, for they do not find conditions

favorable for multiplication on the skin of man.

Tarsonemidae

The representatives of the family TARSONEMIDAE are minute mites, with the

body divided into cephalothorax and abdomen. There is marked sexual

dimorphism. The females possess stigmata at the anterior part of the

body, at the base of the rostrum, and differ from all other mites in

having on each side, a prominent clavate organ between the first and

second legs. The larva, when it exists, is hexapodous and resembles the

adult. A number of the species are true parasites on insects, while

others attack plants. Several of them may be accidental parasites of

man.

[Illustration: 52. Pediculoides ventricosus, female. After Webster.]

[Illustration: 53. Pediculoides ventricosus, gravid female. (x80).

After Webster.]

_Pediculoides ventricosus_ (fig. 52 and 53) is, of all the

Tarsonemidae reported, the one which has proved most troublesome to

man. It is a predaceous species which attacks a large number of insects

but which has most commonly been met with by man through its fondness

for certain grain-infesting insects, notably the Angoumois grain moth,

_Sitotroga cerealella_, and the wheat straw-worm, _Isosoma grande_. In

recent years it has attracted much attention in the United States and

its distribution and habits have been the object of detailed study by

Webster (1901).

[Illustration: 54. Pediculoides ventricosus, male. After Braun.]

There is a very striking sexual dimorphism in this species. The

non-gravid female is elongate, about 200u by 70u (fig. 52), with the

abdomen slightly striated longitudinally. The gravid female (fig. 53)

has the abdomen enormously swollen, so that it is from twenty to a

hundred times greater than the rest of the body. The species is

viviparous and the larvae undergo their entire growth in the body of the

mother. They emerge as sexually mature males and females which soon

pair. The male (fig. 54) is much smaller, reaching a length of only 320u

but is relatively broad, 80u, and angular. Its abdomen is very greatly

reduced.

As far back as 1850 it was noted as causing serious outbreaks of

peculiar dermatitis among men handling infested grain. For some time the

true source of the difficulty was unknown and it was even believed that

the grain had been poisoned. Webster has shown that in this country (and

probably in Europe as well) its attacks have been mistaken for those of

the red bugs or "chiggers" (larval Trombiidae). More recently a number of

outbreaks of a mysterious "skin disease" were traced to the use of straw

mattresses, which were found to be swarming with these almost

microscopic forms which had turned their attentions to the occupants of

the beds. Other cases cited were those of farmers running wheat through

a fanning mill, and of thrashers engaged in feeding unthrashed grain

into the cylinder of the machine.

[Illustration: 55. Lesions produced by the attacks of Pediculoides

ventricosus. After Webster.]

The medical aspects of the question have been studied especially by

Schamberg and Goldberger and from the latter's summary (1910) we derive

the following data. Within twelve to sixteen hours after exposure,

itching appears and in severe cases, especially where exposure is

continued night after night by sleeping on an infested bed, the itching

may become almost intolerable. Simultaneously, there appears an eruption

which characteristically consists of wheals surrounded by a vesicle

(fig. 55). The vesicle as a rule does not exceed a pin head in size but

may become as large as a pea. Its contents rapidly become turbid and in

a few hours it is converted into a pustule. The eruption is most

abundant on the trunk, slight on the face and extremities and almost

absent on the feet and hands. In severe cases there may be

constitutional disturbances marked, at the outset, by chilliness,

nausea, and vomiting, followed for a few days by a slight elevation of

temperature, with the appearance of albumin in the urine. In some cases

the eruption may simulate that of chicken-pox or small-pox.

Treatment for the purpose of killing the mites is hardly necessary as

they attach feebly to the surface and are readily brushed off by

friction of the clothes. "Antipruritic treatment is always called for;

warm, mildly alkaline baths or some soothing ointment, such as zinc

oxide will be found to fulfil this indication." Of course, reinfestation

must be guarded against, by discarding, or thoroughly fumigating

infested mattresses, or by avoiding other sources. Goldberger suggests

that farm laborers who must work with infested wheat or straw might

protect themselves by anointing the body freely with some bland oil or

grease, followed by a change of clothes and bath as soon as their work

is done. We are not aware of any experiments to determine the effect of

flowers of sulphur, but their efficiency in the case of "red bugs"

suggests that they are worth a trial against _Pediculoides_.

Various species of TYROGLYPHIDAE (fig. 150_f_) may abound on dried fruits

and other products and attacking persons handling them, may cause a

severe dermatitis, comparable to that described above for _Pediculoides

ventricosus_. Many instances of their occurrence as such temporary

ectoparasites are on record. Thus, workers who handle vanilla pods are

subject to a severe dermatitis, known as vanillism, which is due to the

attacks of _Tyroglyphus siro_, or a closely related species. The

so-called "grocer's itch" is similarly caused by mites infesting various

products. Castellani has shown that in Ceylon, workers employed in the

copra mills, where dried cocoanut is ground up for export, are much

annoyed by mites, which produce the so-called "copra itch." The skin of

the hands, arms and legs, and sometimes of the whole body, except the

face, is covered by fairly numerous, very pruriginous papules, often

covered by small, bloody crusts due to scratching. The condition is

readily mistaken for scabies. It is due to the attacks of _Tyroglyphus

longior castellanii_ which occur in enormous numbers in some samples of

the copra.

Sarcoptidae

The SARCOPTIDAE are minute whitish mites, semi-globular in shape, with a

delicate transversely striated cuticula. They lack eyes and tracheae. The

mouth-parts are fused at the base to form a cone which is usually

designated as the head. The legs are short and stout, and composed of

five segments. The tarsi may or may not possess a claw and may terminate

in a pedunculated sucker, or simple long bristle, or both. The presence

or absence of these structures and their distribution are much used in

classification. The mites live on or under the skin of mammals and

birds, where they produce the disease known as scabies, mange, or itch.

Several species of the Sarcoptidae attack man but the most important of

these, and the one pre-eminent as the "itch mite" is _Sarcoptes

scabiei_.

The female of _Sarcoptes scabiei_, of man, is oval and yellowish white;

the male more rounded and of a somewhat reddish tinge, and much smaller.

The body is marked by transverse striae which are partly interrupted on

the back. There are transverse rows of scales, or pointed spines, and

scattered bristles on the dorsum.

[Illustration: 56_a_. Sarcoptes scabiei, male. (x100). After

Furstenberg.]

The male (fig. 56) which is from 200-240u in length, and 150-200u in

breadth, possesses pedunculated suckers on each pair of legs except the

third, which bears, instead, a long bristle. The female (fig. 56)

300-450u in length and 250-350u in breadth, has the pedunculated suckers

on the first and second pairs of legs, only, the third and fourth

terminating in bristles.

[Illustration: 56_b_. Sarcoptes scabiei, female. (x100.) After

Furstenberg.]

The mite lives in irregular galleries from a few millimeters to several

centimeters in length, which it excavates in the epidermis (fig. 57). It

works especially where the skin is thin, such as between the fingers, in

the bend of the elbows and knees, and in the groin, but it is by no

means restricted to these localities. The female, alone, tunnels into

the skin; the males remain under the superficial epidermal scales, and

seldom are found, as they die soon after mating.

As she burrows into the skin the female deposits her eggs, which measure

about 150 x 100u. Furstenberg says that each deposits an average of

twenty-two to twenty-four eggs, though Gudden reports a single burrow as

containing fifty-one. From these there develop after about seven days,

the hexapod larvae. These molt on the sixteenth day to form an octopod

nymph, which molts again the twenty-first day. At the end of the fourth

week the nymphs molt to form the sexually mature males and the so-called

pubescent females. These pair, the males die, and the females again cast

their skin, and become the oviparous females. Thus the life cycle is

completed in about twenty-eight days.

The external temperature exercises a great influence on the development

of the mites and thus, during the winter, the areas of infestation not

only do not spread, but they become restricted. As soon as the

temperature rises, the mites increase and the infestation becomes much

more extensive.

[Illustration: 57. Sarcoptes scabiei. Diagrammatic representation of the

course in the skin of man.]

In considering the possible sources of infestation, and the chances of

reinfestation after treatment, the question of the ability of the mite

to live apart from its host is a very important one. Unfortunately there

are few reliable data on this subject. Gerlach found that, exposed in

the dry, warm air of a room they became very inactive within twenty-four

hours, that after two days they showed only slight movement, and that

after three or four days they could not be revived by moisture and

warming. The important fact was brought out that in moist air, in folded

soiled underwear, they survived as long as ten days. Bourguignon found

that under the most favorable conditions the mites of _Sarcoptes scabiei

equi_ would live for sixteen days.

The disease designated the "itch" or "scabies," in man has been known

from time immemorial, but until within less than a hundred years it was

almost universally attributed to malnutrition, errors of diet, or "bad

blood." This was in spite of the fact that the mite was known to Mouffet

and that Bonomo had figured both the adult and the egg and had declared

the mite the sole cause of the disease. In 1834 the Corsican medical

student, Francis Renucci, demonstrated the mite before a clinic in Saint

Louis Hospital in Paris and soon thereafter there followed detailed

studies of the life history of the various itch mites of man and

animals.

[Illustration: 58. Scabies on the hand. From portfolio of Dermochromes

by permission of Rebman & Co., of New York. Publishers.]

The disease is a cosmopolitan one, being exceedingly abundant in some

localities. Its spread is much favored where large numbers of people are

crowded together under insanitary conditions and hence it increases

greatly during wars and is widely disseminated and abundant immediately

afterwards. Though more commonly to be met with among the lower classes,

it not infrequently appears among those of the most cleanly, careful

habits, and it is such cases that are most liable to wrong diagnosis by

the physician.

Infection occurs solely through the passage, direct or indirect, of the

young fertilized females to the skin of a healthy individual. The adult,

oviparous females do not quit their galleries and hence do not serve to

spread the disease. The young females move about more or less at night

and thus the principal source of infestation is through sleeping in the

same bed with an infested person, or indirectly through bedclothes, or

even towels or clothing. Diurnal infestation through contact or clothing

is exceptional. Many cases are known of the disease being contracted

from animals suffering from scabies, or mange.