The species of _Miltogramma_—of which there are many in Europe and two in

England—live at the expense of Fossorial {509}Hymenoptera by a curious sort

of indirect parasitism. They are obscure little flies, somewhat resembling

the common House-fly, but they are adepts on the wing and have the art of

ovipositing with extreme rapidity; they follow a Hymenopteron as it is

carrying the prey to the nest for its young. When the wasp alights on the

ground at the entrance to the nest, the _Miltogramma_ swoops down and

rapidly deposits one or more eggs on the prey the wasp designs as food for

its own young. Afterwards the larvae of the fly eat up the food, and in

consequence of the greater rapidity of their growth, the young of the

Hymenopteron perishes. Some of them are said to deposit living larvae, not

eggs. Fabre has drawn a very interesting picture of the relations that

exist between a species of _Miltogramma_ and a Fossorial Wasp of the genus

_Bembex_[432]. We may remind the reader that this Hymenopteron has not the

art of stinging its victims so as to keep them alive, and that it

accordingly feeds its young by returning to the nest at proper intervals

with a fresh supply of food, instead of provisioning the nest once and for

all and then closing it. This Hymenopteron has a habit of catching the

largest and most active flies—especially Tabanidae—for the benefit of its

young, and it would therefore be supposed that it would be safe from the

parasitism of a small and feeble fly. On the contrary, the _Miltogramma_

adapts its tactics to the special case, and is in fact aided in doing so by

the wasp itself. As if knowing that the wasp will return to the

carefully-closed nest, the _Miltogramma_ waits near it, and quietly selects

the favourable moment, when the wasp is turning round to enter the nest

backwards, and deposits eggs on the prey. It appears from Fabre's account

that the _Bembex_ is well aware of the presence of the fly, and would seem

to entertain a great dread of it, as if conscious that it is a formidable

enemy; nevertheless the wasp never attacks the little fly, but allows it

sooner or later to accomplish its purpose, and will, it appears, even

continue to feed the fly-larvae, though they are the certain destroyers of

its own young, thus repeating the relations between cuckoo and sparrow.

Most of us think the wasp stupid, and find its relations to the fly

incredible or contemptible. Fabre takes a contrary view, and looks on it as

a superior Uncle Toby. We sympathise with the charming French naturalist,

without forming an opinion.

{510}Doubtless there are many other interesting features to be found in the

life-histories of Tachinidae, for in numbers they are legion. It is

probable that we may have 200 species in Britain, and in other parts of the

world they are even more abundant, about 1000 species being known in North

America.[433] The family Actiidae is at present somewhat doubtful.

According to Karsch,[434] it is a sub-family of Tachinidae; but the fourth

longitudinal vein, it appears, is straight.

FAM. 36. DEXIIDAE.—_These Insects are distinguished from Tachinidae by the

bristle of the antennae being pubescent, and the legs usually longer._ The

larvae, so far as known, are found in various Insects, especially in

Coleoptera, and have also been found in snails. There are eleven British

genera, and about a score of species.

FAM. 37. SARCOPHAGIDAE.—_Distinguished from Muscidae and Tachinidae by

little more than that the bristle of the antennae is feathery at the base

but hair-like and very fine at the tip._—_Sarcophaga carnaria_ is one of

the commonest British Insects; it is like the Blow-fly, though rather

longer, conspicuously grey and black, with the thorax distinctly striped,

and the pulvilli very conspicuous in the live fly. _Cynomyia mortuorum_ is

a bright blue fly rather larger than the Blow-fly, of which it is a

competitor; but in this country an unsuccessful one. The larvae of the two

Insects are found together, and are said to be quite indistinguishable.

_Cynomyia_ is said to lay only about half the number of eggs that the

Blow-fly does, but it appears earlier in the year, and to this is

attributed the fact that it is not altogether crowded out of existence by

the more prolific _Calliphora_. The species of Sarcophagidae are usually

viviparous, and one of them, _Sarcophila magnifica_ (_wohlfahrti_), has the

habit of occasionally depositing its progeny in the nostrils of mammals,

and even of human beings, causing horrible sufferings and occasionally

death: it is said to be not uncommon in Europe but does not occur in

Britain. The genus _Sarcophaga_ is numerous in species, and many of them

are beneficial. Sir Sidney Saunders found in the Troad that Locusts were

destroyed by the larvae of a _Sarcophaga_ living in their bodies; and

{511}Künckel has recently observed that in Algeria several species of this

genus attack Locusts and destroy large quantities by depositing living

larvae in the Orthoptera. In North America the Army-worm is decimated by

species of _Sarcophaga_.

Many of these Insects, when food is scarce, eat their own species with

eagerness, and it seems probable that this habit is beneficial to the

species. The parent-fly in such cases usually deposits more eggs than there

is food for, thus ensuring that every portion of the food will be rapidly

consumed, after which the partially-grown larvae complete their development

by the aid of cannibalism. It is thus ensured that the food will raise up

as many individuals as possible.

FAM. 38. MUSCIDAE.—_Bristle of antennae feathered._ This family contains

many of the most abundant flies, including the House-fly, Blue-bottles or

Blow-flies, Green-bottles, and other forms which, though very common, are

perhaps not discriminated from one another by those who are not

entomologists. The larvae live on carrion and decaying or excrementitious

matters. The common House-fly, _Musca domestica_, runs through its

life-history in a very short time. It lays about 150 very small eggs on

dung or any kind of soft damp filth; the larvae hatch in a day or two and

feed on the refuse; they may be full-grown in five or six days, and, then

pupating, may in another week emerge as perfect flies. Hence it is no

wonder that they increase to enormous numbers in favourable climates. They

are thought to pass the winter chiefly in the pupal state. The House-fly is

now very widely distributed over the world; it sometimes occurs in large

numbers away from the dwellings of man. Of Blow-flies there are two common

species in this country, _Calliphora erythrocephala_ and _C. vomitoria_.

The Green-bottle flies, of which there are several species, belonging to

the genus _Lucilia_, have the same habits as Blow-flies, though they do not

commonly enter houses. The larvae are said to be indistinguishable from

those of _Calliphora_.

The larvae of Eumyiid Muscidae are, when first hatched, metapneustic, but

subsequently an anterior pair of stigmata appears, so that the larva

becomes amphipneustic. They usually go through three stages, distinguished

by the condition of the posterior stigmata. In the early instar these have

a single heart-shaped fissure, in the second stage two fissures exist,

{512}while in the third instar there is a greater diversity in the

condition of the breathing apertures.

The various forms of Muscidae show considerable distinctions in the details

of their natural history, and these in certain species vary according to

the locality. This subject has been chiefly studied by Portschinsky, a

Russian naturalist, and a very interesting summary of his results has been

given by Osten Sacken,[435] to which the student interested in the subject

will do well to refer.

A few years ago a great deal of damage was caused in the Netherlands by

_Lucilia sericata_, a Green-bottle-fly, extremely similar to our common _L.

caesar_, which deposited its eggs in great quantities on sheep amongst

their wool. This epidemic was attributed to the importation of sheep from

England; but, according to Karsch, there is reason to suppose that the fly

was really introduced from Southern Europe or Asia Minor.[436]

The larvae of species of the genus _Lucilia_ sometimes attack man and

animals in South America, but fortunately not in this country. The larva of

_Lucilia_ (_Compsomyia_) _macellaria_ is called the screw-worm, and is the

best known of the forms that infest man, the larvae living in the nasal

fossae and frontal sinuses, and causing great suffering. The fly is common

in North America, but is said never to attack man farther north than in

Kansas. A little fly (_Stomoxys calcitrans_), very like the common

house-fly though rather more distinctly spotted with grey and black, and

with a fine, hard, exserted proboscis, frequently enters our houses and

inflicts a bite or prick on us. It is commonly mistaken for an ill-natured

house-fly that has taken to biting. It is frequently a source of irritation

to cattle. A closely allied fly, _Haematobia serrata_, is very injurious to

cattle in North America, but the same species causes no serious annoyance

in England. We may mention that the various attacks of Dipterous larvae on

man have received the general name "myiasis."

The Tse-tse fly (_Glossina morsitans_), another ally of _Stomoxys_, is not

very dissimilar in size and shape to the blow-fly.[437] {513}It bites man

and animals in South Africa, and if it have previously bitten an animal

whose blood was charged with the Haematozoa that really constitute the

disease called Nagana (fly-disease), it inoculates the healthy animal with

the disease; fortunately only some species are susceptible, and man is not

amongst them. It has recently been shown by Surgeon Bruce[438] that this

fly multiplies by producing, one at a time, a full-grown larva, which

immediately changes to a pupa, as do the members of the series Pupipara.

There are already known other Muscid flies with peculiarities in their

modes of reproduction, so that it is far from impossible that the various

conditions between ordinary egg-laying and full-grown larva- or

pupa-production may be found to exist. Although it has been supposed that

the Tse-tse fly is a formidable obstacle to the occupation of Africa by

civilised men, there is reason to suppose that this will not ultimately

prove to be the case. It only produces disease when this pre-exists in

animals in the neighbourhood; only certain species are liable to it; and

there is some evidence to the effect that even these may in the course of a

succession of generations become capable of resisting the disease

inoculated by the fly. As long ago as 1878 Dr. Drysdale suggested[439] that

this fly only produces disease by inoculating a blood-parasite, and all the

evidence that has since been received tends to show that his idea is

correct.

[Illustration: Fig. 244—The Tse-tse fly (_Glossina morsitans_). A, The fly

with three divisions of the proboscis projecting; B, adult larva; C, pupa.]

Although the facts we have mentioned above would lead to the supposition

that Muscidae are unmitigated nuisances, yet it is probable that such an

idea is the reverse of the truth, and that on the whole their operations

are beneficial. It would be difficult to overestimate their value as

scavengers. And in addition to this they destroy injurious creatures. Thus

in Algeria _Idia fasciata_, a fly like the House-fly, destroys the

{514}dreaded migratory Locust _Schistocerca peregrina_ in great quantities,

by the larvae eating the eggs of the Locust. The female of this fly, in

order to reach the desired food, penetrates from one to three inches below

the surface of the ground.

FAM. 39. OESTRIDAE (_Bot-flies_).—_Rather large or very large flies, with

extremely short antennae, bearing a segmented arista, the front of the head

prominent, the posterior part of the wings frequently rough, and with but

few veins: the mouth usually atrophied, the trophi being represented only

by tubercles; larvae living in Vertebrates, usually Mammals, though it is

possible that a few occur in Birds and even in Reptiles._ This is a family

of small extent, less than 100 species being known from all the world, yet

it is of much interest on account of the habits of its members, which,

though of large size, live entirely at the expense of living Vertebrates,

to the viscera or other structures of which they have definite relations,

varying according to the species. Some (_Gastrophilus_, etc.) live in the

alimentary canal; others (_Hypoderma_, etc.) are encysted in or under the

skin; while others (_Oestrus_, etc.) occupy the respiratory passages. As

many of them attack the animals used by man, and some of them do not spare

man himself, they have attracted much attention, and there is an extensive

literature connected with them; nevertheless the life-histories are still

very incompletely known. Indeed, the group is from all points of view a

most difficult one, it being almost impossible to define the family owing

to the great differences that exist in important points. Some think the

family will ultimately be dismembered; and Girschner has recently proposed

to treat it as a division of Tachinidae. The chief authority is Brauer, in

whose writings the student will find nearly all that is known about

Oestridae.[440] Some of them exist in considerable numbers (it is believed

that they are now not so common as formerly), and yet the flies are but

rarely met with, their habits being in many respects peculiar. Some of

them, for purposes of repose, frequent the summits of mountains, or towers,

or lofty trees. Some have great powers of humming; none of them are known

to bite their victims, indeed the atrophied mouth of most of the Oestridae

forbids such a proceeding.

{515}[Illustration: Fig. 245—_Cephalomyia maculata_, a Bot-fly of the

camel. Arabia. A, The fly with extended wings; B, under aspect of the head:

_a_, antenna; _b_, the obsolete mouth-parts.]

Some deposit their eggs on the hairs of the beasts from which the larvae

are to draw their nutriment, but others place their larvae, already

hatched, in the entrances of the nasal passages. They do not feed on the

blood or tissues of their victims, but on the secretions, and these are

generally altered or increased by the irritation induced by the presence of

the unwelcome guests. It would appear, on the whole, that their presence is

less injurious than would be expected, and as they always quit the bodies

of their hosts for the purposes of pupation, a natural end is put to their

attacks. We have ten species in Britain, the animals attacked being the ox,

the horse, the ass, the sheep, and the red deer; others occasionally occur

in connexion with animals in menageries. The eggs of _Gastrophilus equi_

are placed by the fly, when on the wing, on the hair of horses near the

front parts of the body, frequently near the knee, and, after hatching, the

young larvae pass into the stomach of the horse either by being licked off,

or by their own locomotion; in the stomach they become hooked to the walls,

and after being full grown pass out with the excreta: the Bots—as these

larvae are called—are sometimes very numerous in the stomach, for a fly

will lay as many as four or five hundred eggs on a single horse: in the

case of weakly animals, perforation of the stomach has been known to occur

in consequence of the habit of the Bot of burying itself to a greater or

less extent in the walls of the stomach. _Hypoderma bovis_ and _H. lineata_

attack the ox, and the larvae cause tumours in the skin along the middle

part of the back. It was formerly {516}inferred from this that the fly

places its eggs in this situation, and as the cattle are known to dread and

flee from the fly, it was supposed to be on account of the pain inflicted

when the egg was thrust through the skin. Recent observations have shown

that these views are erroneous, but much still remains to be ascertained.

The details of oviposition are not yet fully known, but it appears that the

eggs are laid on the lower parts of the body, especially near the heels,

and that they hatch very speedily.[441] As the imago of _Hypoderma_ appears

for only a very short period in the summer, the time of the oviposition is

certain. The newly-disclosed larva is considerably different from the more

advanced instar found in the skin of the back; moreover, a long period of

many months intervenes between the hatching of the larva and its appearance

in the part mentioned. Brauer has shown that when the grub is first found

in that situation it is entirely subcutaneous. Hence it would be inferred

that the newly-hatched larva penetrated the skin probably near the spot it

was deposited on, and passed a period in subcutaneous wandering, on the

whole going upwards till it arrived at the uppermost part: that after

moulting, and in consequence of greater need for air, it then pierced the

skin, and brought its breathing organs into contact with the external air;

that the irritation caused by the admission of air induced a purulent

secretion, and caused the larva to be enclosed in a capsule. Dr. Cooper

Curtice has however found, in the oesophagus of cattle, larvae that he

considers to be quite the same as those known to be the young of

_Hypoderma_; and if this prove to be correct, his inference that the young

larvae are licked up by the cattle and taken into the mouth becomes

probable. The larva, according to this view, subsequently pierces the

oesophagus and becomes subcutaneous by passing through the intervening

tissues. The later history of the grub is briefly, that when full grown it

somewhat enlarges the external orifice of its cyst, and by contractions and

expansions of the body, passes to the surface, falls to the ground, buries

itself and becomes a pupa. If Dr. Curtice be correct, there should, of

course, be as many, if not more, larvae found in the oesophagus as in the

back of the animal; but, so far as is known, this is not the case, and we

shall not be surprised if the normal course of development be found

different from what Dr. Curtice supposes it to be. His {517}observations

relate to _Hypoderma lineata_. Our common British species is usually

supposed to be _H. bovis_; but from recent observations it seems probable

that most of the "Ox-warbles" of this country are really due to the larvae

of _H. lineata_.

The history of _Oestrus ovis_, which attacks the sheep, is also

incompletely known, but appears to be much simpler. This fly is viviparous,

and deposits its young larvae at the entrance of the nasal passages of the

sheep, thereby causing extreme annoyance to the animal. The larvae

penetrate to the frontal sinuses to complete their growth. The duration of

their lives is unknown, for it is commonly the case that larvae of various

sizes are found together. _Cephenomyia rufibarbis_ has recently been found

in Scotland. It attacks the Red deer, and its life-history is similar to

that of _Oestrus ovis_, though the larvae apparently prefer to attain their

full growth in the pharynx of the deer.

In reference to the Oestridae that attack man, we may merely mention that

the larva of the _Hypoderma_ of the ox is occasionally found in Europe

infesting human beings, but only as an extremely rare and exceptional

event; and that only those engaged in attending on cattle are attacked;

from which it is inferred that the flies are deceived by an odour emanating

from the garments. In America numerous cases are known of Oestrid larvae

being taken from the body of man, but information about them is very

scanty. It appears, however, that there are at least four species, one of

which, _Dermatobia noxialis_, is known as a fly as well as a larva. Whether

any of these are peculiar to man is uncertain.[442] There are several

larvae of Muscidae that have similar habits to the Oestridae; hence the

statements that exist as to larvae being found in birds and reptiles cannot

be considered to apply to members of the latter family until the larvae

have been studied by an expert.

The family Ctenostylidae has been established by Bigot for a South American

Insect, of which only a single individual exists in collections. It is

doubtful whether it can be referred to Oestridae.[443]

SERIES V. PUPIPARA

The four families included in this Series are, with the exception of the

Hippoboscidae, very little known. Most of {518}them live by sucking blood

from Mammals and Birds, and sometimes they are wingless parasites. The

single member of the family Braulidae lives on bees. The term Pupipara is

erroneous, and it would be better to revert to Réaumur's prior appellation

Nymphipara. Müggenburg has suggested that the division is not a natural

one, the points of resemblance that exist between its members being

probably the results of convergence. Recent discoveries as to the modes of

bringing forth of Muscidae give additional force to this suggestion. A

satisfactory definition of the group in its present extent seems

impossible.

FAM. 40. HIPPOBOSCIDAE.—_Wings very variable, sometimes present and large,

then with waved surface and thick nervures confined to the anterior and

basal part; sometimes mere strips, sometimes entirely absent._ Certain

members of this family are well known, the Forest-fly, or Horse-fly, and

the Sheep-tick belonging to it. The proboscis is of peculiar formation, and

not like that of other flies. Seen externally it consists of two elongate,

closely adapted, hard flaps; these are capable of diverging laterally to

allow an inner tube to be exserted from the head. The details and

morphology of the structure have recently been discussed by

Müggenburg.[444] _Melophagus ovinus_, commonly called the Sheep-tick, is

formed for creeping about on the skin of the sheep beneath the wool, and

may consequently be procured with ease at the period of sheep-shearing: it

has no resemblance to a fly, and it is difficult to persuade the

uninitiated that it is such. _Hippobosca equina_ (called in this country

the Forest-fly, perhaps because it is better known in the New Forest than

elsewhere), looks like a fly, but will be readily recognised by the two

little cavities on the head, one close to each eye, in which the antennae

are concealed, only the fine bristle projecting. Very little seems to be

known as to the Natural History of this fly. _Lipoptena cervi_ lives on the

Red deer; the perfect Insect has apparently a long life, and both sexes may

be found in a wingless state on the deer all through the winter. When first

disclosed in the summer they are however provided with wings, but when they

have found a suitable host they bite off, or cast, the wings. The female,

it appears, does this more promptly than the male, so that it is difficult

to get winged individuals of the former sex.[445]

{519}[Illustration: Fig. 246.—Diagrammatic section of the larva of

_Melophagus ovinus_. (After Pratt.) _a_, mouth; _b_, suctorial pouch; _c_,

imaginal disc for adult head; _d_, meso- and meta-notal discs; _e_,

anterior tracheal anastomosis; _f_, first muscular belt; _g_, transverse

tracheal branch; _h_, the dorsal tracheal tube; _i_, sex-organ; _k_,

Malpighian tube; _l_, terminal part of intestine; _m_, terminal chamber of

tracheal tube; _n_, stigmatic fossa; _o_, terminal part of intestine; _p_,

anus; _q_, anal disc; _r_, ventral tracheal tube; _s_, stomach; _t_,

nervous system; _u_, discs for the three pairs of legs of the imago; _v_,

ventral pouch; _w_, pharynx; _x_, suctorial lip.]

Most of the known Hippoboscidae live on birds, and are apparently specially

fond of the Swallow tribe. They are all winged, though in some species the

wings are very small. The bird-infesting Hippoboscidae have been very

little studied, and will probably form a distinct family; the antennae of

_Stenopteryx hirundinis_ are quite different from those of _Hippobosca_.

The development is remarkable, and has been studied by Leuckart[446] and by

Pratt[447] in the case of _Melophagus ovinus_. The ovaries are peculiarly

formed, and produce one large egg at a time; this passes into the dilated

oviduct, and there goes through its full growth and a certain amount of

development; it is then extruded, and undergoing little or no change of

form becomes externally hardened by the excretion of chitin, passing thus

into the condition of the Eumyiid pupa. Dufour thought that there is no

larval stage in this Insect, but it is quite clear from later researches

that he was wrong, and that a larval stage of a peculiar kind, but in some

respects resembling that of the Eumyiid Muscidae, occurs. The larva has no

true head, but the anterior part of the body is invaginated, and the most

anterior part again protrudes in the invagination, so that two little

passages appear on section (Fig. 246); the upper one leads to the stomach,

which is of very large size. The tracheal system is peculiar; it is

metapneustic, there being neither anterior nor lateral spiracles. Pratt

says that there is at first a single pair of terminal spiracles, and

subsequently three pairs, hence he considers that the terminal part of the

body corresponds to three segments. This is however probably a mistaken

view; it appears more probable that the so-called three pairs of stigmata

really correspond with the complex {520}condition of the stigmata in the

later instars of certain other Dipterous larvae. The _Melophagus_-larva is

nourished by secretion from certain glands of the mother-fly; this is

swallowed and the stomach is greatly distended by this milky fluid.

Probably it was this condition that induced Dufour to suppose the larva to

be only an embryo.

Some of the Hippoboscidae that live on birds take to the wing with great

readiness, and it is probable that these bird-parasites will prove more

numerous than is at present suspected.

We may here notice an animal recently described by Dr. Adensamer and called

_Ascodipteron_.[448] He treats it as the female imago of a Pupiparous

Dipteron. It was found buried in the skin of the wing of a bat of the genus

_Phyllorhina_, in the Dutch East Indies, only one individual being known.

It is entirely unsegmented, and externally without head. If Dr. Adensamer

should prove to be correct in his surmise the creature can scarcely be

inferior in interest to the Strepsiptera.

[Illustration: Fig. 247.—_Braula coeca._ × 18/1. (After Meinert.)]

FAM. 41. BRAULIDAE.—This consists only of a minute Insect that lives on

bees. The antennae are somewhat like those of the sheep-tick, though they

are not so completely concealed in the cavities in which they are inserted.

According to Müggenburg[449] a ptilinum exists, and he is also of opinion

that although the parts of the mouth differ very much from those of

Hippoboscidae they are essentially similar. Lucas says that _Braula_

specially affects the thorax of the bee: Müggenburg, that it is fond of the

queen-bee because of the exposed membranes between the body-segments that

exist in that sex. Whether this Insect is truly Pupiparous is unknown,

though Boise states that a pupa is deposited in the cell of the bee by the

side of the young larva of {521}the bee, and appears as the perfect Insect

in about twenty-one days. Müggenburg suggests that _Braula_ may be

oviparous, as he has never found a larva in the abdomen. Packard says that

on the day the larva hatches from the egg it sheds its skin and turns to an

oval puparium of a dark brown colour. The Insect is frequently though

inappropriately called bee-louse; notwithstanding its name it is not quite

blind, though the eyes are very imperfect.

FAM. 42. STREBLIDAE.— _Winged; possessing halteres; the head small, narrow

and free._ These very rare Diptera are altogether problematic. According to

Kolenati the larvae live in bats' excrement and the perfect Insects on the

bats.[450] If the former statement be correct the Insects can scarcely

prove to be Pupipara. The wing-nervuration is, in the figures of the

Russian author, quite different from that of Hippoboscidae. The Streblidae

have been associated by some entomologists with Nycteribiidae, and by

Williston with Hippoboscidae.

[Illustration: Fig. 248.—_Nycteribia_ sp., from _Xantharpyia straminea_.

Aden. A, Upper surface of female, with head in the position of repose; B,

under surface of male. x 12/1.]

FAMILY 43. NYCTERIBIIDAE.—The species of this family are found on bats;

they are apparently rare, and we have been able to examine only one

species. The form is very peculiar, the {522}Insects looking as if the

upper were the under surface. They are wingless, with a narrow head, which

reposes on the back of the thorax. The prothorax appears to be seated on

the dorsum of the mesothorax. According to Müggenburg there is no trace of

a ptilinum. A brief note on the metamorphosis[451] by Baron Osten Sacken

indicates that the mature larva differs from that of _Melophagus_ in the

arrangement of the stigmata; they appear to be dorsal instead of terminal.

There are apparently no characters of sufficient importance to justify the

association of these Insects with the other divisions of Pupipara; the sole

ground for this connection being the supposed nature of the life-history of

the larva.

[Illustration: Fig. 249—Anterior part of the body of _Nycteribia_ sp.,

found on _Xantharpyia straminea_ by Colonel Yerbury at Aden. A, Upper

surface of female, with head extended; B, under surface of male, with head

extended; C, claws of a foot.]

SUB-ORDER APHANIPTERA or SIPHONAPTERA (_Fleas_)

FAM. PULICIDAE.—_Wingless, with the body laterally compressed, so that the

transverse diameter is small, the vertical one great. The head indistinctly

separated from the body, small, with short thick antennae placed in

depressions somewhat behind and above the unfaceted eyes. These are always

minute, and sometimes wanting._

{523}[Illustration: Fig. 250—_Hystrichopsylla talpae._ Britain. (After

Ritsema.)]

[Illustration: Fig. 251.—Mouth-parts of a flea, _Vermipsylla alakurt_ ♂.

_H._ Unpaired pricking organ; _Lp._ labial palp; _Md._ mandible; _Mx._

maxilla; _Mxp._ maxillary palp. (After Wagner.)]

We all know that the Flea is so flat, or compressed sideways, that it does

not mind the most severe squeeze. This condition is almost peculiar to it;

a great flattening of the body is common in Insects—as is seen in another

annoying Insect, the bed-bug—but the compression, in the flea, is in the

reverse direction. In other respects the external anatomy of the flea shows

several peculiarities, the morphological import of which has not yet been

elucidated. The head is of very peculiar shape, small, with the antennae

placed in an unusual position; the clypeus is said to be entirely absent,

the front legs are articulated in such a manner that they have a large

additional basal piece—called by some anatomists the ischium—and in

consequence appear to be placed far forwards, looking as if they were

attached to the head; the meso- and meta-thorax have certain flaps that

have been considered to be homologues of wings; and the maxillary palpi are

attached to the head in such a way that they appear to play the part of the

antennae of other Insects (Fig. 250), and were actually considered to be

the antennae by Linnaeus, as well as others; the mouth-parts themselves are

differently constructed from those of any other Insects.[452] The maxillae

and labium are considered to be not only present, but well developed, the

former possessing palpi moderately well developed, while the labial palps

are very large and of highly peculiar form, being imperfectly transversely

jointed and acting as sheaths; the mandibles are present in the form of a

pair of elongate, slender organs, with serrated edges; and there is an

unpaired, elongate pricking-organ, thought by some to be a hypopharynx, and

by others a labrum.

{524}[Illustration: Fig. 252—Larva of _Pulex serraticeps_, the dog- and

cat-flea. (After Künckel.)]

The antennae are of unusual form, consisting of two basal joints, and,

loosely connected therewith, a terminal mass of diverse form and more or

less distinctly, though irregularly, segmented. The full number of ten

stigmata exists, Wagner giving three thoracic, with seven abdominal, placed

on segments 2-8 of the abdomen; but Packard thinks the supposed

metathoracic stigma is really the first abdominal. Fleas undergo a very

complete metamorphosis; the larvae are wormlike, resembling those of

Mycetophilid Diptera (Fig. 252). The egg of the cat's flea is deposited

among the fur of the animal, but (unlike the eggs of other parasites)

apparently is not fastened to the hair, for the eggs fall freely to the

ground from infested animals; the young larva when hatched bears on the

head a curious structure for breaking the egg-shell. It has the mouth-parts

of a mandibulate Insect and is peripneustic, having ten pairs of stigmata.

It subsequently becomes of less elongate form. Flea-larvae are able to

nourish themselves on almost any kind of refuse animal matter, Laboulbène

having reared them on the sweepings of apartments; they may perhaps

sometimes feed on blood; at any rate the contents of the alimentary canal

appear red through the transparent integuments. When full grown the larva

makes a cocoon, and frequently covers it with pieces of dust. The perfect

flea appears in a week or two thereafter; the pupa has the members free.

The food of the larvae of fleas has been much discussed and a variety of

statements made on the subject. It has been stated that the mother-flea

after being gorged with blood carries some of it to the young, but Künckel

has shown that there is very little foundation for this tale. Enormous

numbers of fleas are sometimes found in uninhabited apartments to which

animals have previously had access, and these fleas will attack in numbers

and with great eagerness any unfortunate person who may enter {525}the

apartment. The cat-flea can pass through its growth and metamorphosis with

excessive rapidity, the entire development of a generation in favourable

conditions extending but little beyond a fortnight.[453]

About a hundred kinds of fleas are known, all of which live on mammals or

birds. _Hystrichopsylla talpae_ (Fig. 250) is one of the largest, it occurs

on the Mole. It was found by Ritsema in the nests of _Bombus subterraneus_

(and was described under the name of _Pulex obtusiceps_). As these nests

are known to be harried by Voles, and as this flea has also been found on

Field-mice, it is probable that the parasites are carried to the nests by

the Voles. The species that chiefly infests man is _Pulex irritans_, an

Insect that is nearly cosmopolitan, though arid desert regions are

apparently unsuitable to it. _Pulex avium_ occurs on a great variety of

birds. _P. serraticeps_ infests the dog and the cat, as well as a variety

of other Mammals. It is a common opinion that each species of Mammal has

its own peculiar flea, but this is far from correct. Fleas pass readily

from one species of animal to another; the writer formerly possessed a cat

that was a most determined and successful hunter of rabbits, and she

frequently returned from her excursions swarming with fleas that she had

become infested with when in the rabbits' burrows; her ears were on some

occasions very sore from the flea-bites. Some of the fleas of other animals

undoubtedly bite man. There appears, however, to be much difference in the

liability of different individuals of our own species to the bites of

fleas. _Sarcopsylla penetrans_ differs in habits from other fleas, as the

female buries the anterior parts of her body in the flesh of man or other

Vertebrates, and the abdomen then becomes enormously enlarged and distended

and undergoes a series of changes that are of much interest.[454] While in

this position the Insect discharges a number of eggs. This species

multiplies sufficiently to become a serious pest in certain regions, the

body of one man having been known to be affording hospitality to 300 of

these fleas. _Sarcopsylla penetrans_ is known as the Sand-flea, or chigger,

and by numerous other names. Originally a native of tropical America it has

been carried to other parts of the world. Another _Sarcopsylla_, _S.

gallinacea_, attaches itself to the eyelids {526}of the domestic fowl in

Ceylon, and an allied form, _Rhynchopsylla pulex_, fastens itself to the

eyelids and other parts of the body of birds and bats in South America. In

Turkestan _Vermipsylla alakurt_ attacks cattle—ox, horse, camel,

sheep—fastening itself to the body of the animal after the fashion of a

tick. Retaining this position all through the winter, it becomes distended

somewhat after the manner of the Sand-flea, though it never forms a

spherical body. The parts of the mouth in this Insect (Fig. 251) are

unusually long, correlative with the thickness of the skins of the animals

on which it lives. Grassi considers that the dog's flea, _Pulex

serraticeps_, acts as the intermediate host of Taenia.

Great difference of opinion has for long prevailed as to whether fleas

should be treated as a Sub-Order of Diptera or as a separate Order of

Insects. Wagner and Künckel, who have recently discussed the question,

think they may pass as aberrant Diptera, while Packard,[455] the last

writer on the subject, prefers to consider them a separate Order more

closely allied to Diptera than to any other Insects. Although widely known

as Aphaniptera, several writers call them Siphonaptera, because Latreille

proposed that name for them some years before Kirby called them

Aphaniptera. Meinert considers them a separate Order and calls it Suctoria,

a most unfortunate name.

ORDER VIII. THYSANOPTERA.

_Small Insects, with a palpigerous mouth placed on the under side of the

head and apposed to the sternum so as to be concealed. With four slender

wings, fringed with long hairs on one or both margins, or with rudiments

of wings, or entirely apterous. Tarsi of one or two joints, terminated by

a vesicular structure. The young resemble the adult in general form, but

there is a pupal stadium in which the Insect is quiescent and takes no

food._

The tiny Insects called Thrips are extremely abundant and may often be

found in profusion in flowers. Their size is only from 1/50 to ⅓ of an inch

in length; those of the latter magnitude are in fact giant species, and so

far as we know at present are found only in Australia (Fig. 253). As

regards the extent {527}of the Order it would appear that Thysanoptera are

insignificant, as less than 150 species are known. Thrips have been,

however, very much neglected by entomologists, so it will not be a matter

for surprise if there should prove to be several thousand species. These

Insects present several points of interest; their mouth-organs are unique

in structure; besides this, they exhibit so many points of dissimilarity

from other Insects that it is impossible to treat them as subdivisions of

any other Order. They have, however, been considered by some to be aberrant

Pseudoneuroptera (cf. Vol. V.), while others have associated them with

Hemiptera. Both Brauer and Packard have treated Thysanoptera as a separate

Order, and there can be no doubt that this is correct. Thysanoptera have

recently been monographed by Uzel in a work that is, unfortunately for most

of us, in the Bohemian language.[456]

[Illustration: Fig. 253—_Idolothrips spectrum._ Australia.]

The antennae are never very long, and are 6 to 9-jointed. The head varies

much, being sometimes elongate and tubular, but sometimes short; it has,

however, always the peculiarity that the antennae are placed quite on its

front part, and that the mouth appears to be absent, owing to its parts

being thrust against the under side of the thorax and concealed. Their most

remarkable peculiarity is that some of them are asymmetrical: Uzel looks on

the peculiar structure, the "Mundstachel," _m_, _m_ {528}(Fig. 254) found

on the left side of the body, as probably an enormous development of the

epipharynx. Previous to the appearance of Uzel's work, Garman had, however,

correctly described the structure of the mouth;[457] he puts a different

interpretation on the parts; he points out that the mandibles (_j_),

so-called by Uzel, are attached to the maxillae, and he considers that they

are really jointed, and that they are lobes thereof; while the Mundstachel

or piercer is, he considers, the left mandible; the corresponding structure

of the other side being nearly entirely absent. He points out that the

labrum and endocranium are also asymmetrical. We think Garman's view a

reasonable one, and may remark that dissimilarity of the mandibles of the

two sides is usual in Insects, and that the mandibles may be hollow for

sucking, as is shown by the larvae of Hemerobiides. There are usually three

ocelli, but they are absent in the entirely apterous forms.

[Illustration: Fig. 254—Face (with base of the antennae) of _Aeolothrips

fasciata_. (After Uzel.) _a_, Labrum; _b_, maxilla with its palp (_c_);

_bl_, terminal part of vertex near attachment of month-parts; _d_, membrane

between maxilla and mentum; _e_, mentum ending in a point near _f_; _g_,

membrane of attachment of the labial palp _h_; _i_, ligula; _j_, _j_ the

bristle-like mandibles; _k_, the thicker base of mandible; _l_, chitinous

lever; _m_, mouth-spine, with its thick basal part _n_, and _o_, its

connection with the forehead, _r_, _r_; _p_, foramen of muscle; _s_ and

_t_, points of infolding of vertex; _u_, a prolongation of the gena.]

The wings appear to spring from the dorsal surface of the body, not from

the sides; the anterior pair is always quite separated from the posterior;

the wings are always slender, sometimes very slender; in other respects

they exhibit considerable variety; sometimes the front pair are different

in colour and consistence from the other pair. The abdomen has ten

segments, the last of which is often tubular in form. The peculiar

vesicular structures by which the feet are terminated are, during movement,

alternately distended and emptied, and have two hooks or claws on the

sides. The stigmata are extremely peculiar, there being four pairs, the

first being the mesothoracic, 2nd {529}metathoracic, 3rd on the second

abdominal segment, 4th on the eighth abdominal segment.[458] There are four

Malpighian tubes, and two or three pairs of salivary glands. The dorsal

vessel is said to be a short sack placed in the 7th and 8th abdominal

segments. The abdominal ganglia of the ventral chain are concentrated in a

single mass, placed in, or close to, the thorax; the thorax has two other

approximated ganglia, as well as an anterior one that appears to be the

infra-oesophageal.

The metamorphosis is also peculiar; the larva does not differ greatly in

appearance from the adult, and has similar mouth-organs and food-habits.

The wings are developed outside the body at the sides, and appear first,

according to Heeger, after the third moult. The nymph-condition is like

that of a pupa inasmuch as no nourishment is taken, and the parts of the

body are enclosed in a skin: in some species there is power of movement to

a slight degree, but other species are quite motionless. In some cases the

body is entirely bright red, though subsequently there is no trace of this

colour. Jordan distinguishes two nymphal periods, the first of which he

calls the pronymphal; in it the Insect appears to be in a condition

intermediate between that of the larva and that of the true nymph; the old

cuticle being retained, though the hypodermis is detached from it and forms

a fresh cuticle beneath it. This condition, as Jordan remarks, seems

parallel to that of the male Coccid, and approaches closely to complete

metamorphosis; indeed the only characters by which the two can be

distinguished appear to be (1) that the young has not a special form; (2)

that the wings are developed outside the body.

Thrips take their food, it is believed, in the same manner as Aphidae, by

suction; but the details of the process are not by any means certain, and

examination of the stomach is said to have resulted in finding pollen

therein. Walsh thought that Thysanoptera pierce and suck Aphidae. An

elaborate inquiry by Osborn[459] failed to elicit satisfactory confirmation

of Walsh's idea, though Riley and Pergande support it to some extent;

Osborn concludes that the ordinary food is not drawn directly from sap, but

consists of exudation or pollen, the tissues {530}of the plant being

pierced only when a supply of food from the usual sources falls short.

Members of this family have been reputed as being very injurious to

cultivated plants, especially to cereals, and it is said that as a result

the harvests in Europe have been seriously diminished. Several species may

take part in the attacks. These appear to be directed chiefly against the

inflorescence. Lindeman thought that _Limothrips denticornis_ (= _Thrips

secalina_), and _Anthothrips aculeata_ (= _Phloeothrips frumentarius_),

were the most destructive species in an attack of Thrips on corn that he

investigated in Russia. Uzel suggests that injuries due to other causes are

sometimes ascribed to Thrips.[460] In hot-houses these Insects are well

known, and sometimes occasion considerable damage to foliage. The German

horticulturalists call them black-fly, in distinction from Aphidae or

green-fly. Some Thysanoptera live under bark, and even in fungi, and in

Australia they form galls on the leaves of trees. This observation is due

to Mr Froggatt, and is confirmed by specimens he sent to the writer.

Vesicular bodies in the leaves of _Acacia saligna_ were traversed on one

side by a longitudinal slit, and on a section being made, nothing but

Thrips, in various stages of growth, was found inside them. A second kind

of gall, forming masses of considerable size on the twigs of _Callistemon_,

is said by Mr Froggatt to be also due to Thrips, as is a third kind on

_Bursaria spinosa_. It is curious that Thrips' galls have not been observed

in other parts of the world.

Thysanoptera are devoured by small bugs of the genus _Triphleps_, as well

as by beetles; a small Acarid attacks them by fixing itself to the body of

the Thrips. Nematode worms and their eggs were found by Uzel in the

body-cavity. He found no less than 200 Nematodes in one Thrips, and noticed

that they had entirely destroyed the ovaries. Woodpeckers, according to

him, tear off the bark of trees and eat the Thysanoptera that are concealed

thereunder, though one would have surmised that these minute Insects are

too small to be game for such birds. They have, it appears, no special

protection, except that one species (a larva of _Phloeothrips_ sp.) is said

to emit a protective fluid.

Parthenogenesis seems to be frequent amongst Thysanoptera, {531}and is

found in concurrence with diversity as to winged and wingless females of

the same species, so as to have given rise to the idea that the phenomena

in this respect are parallel with those that are more widely known as

occurring in Aphidae. Under certain circumstances few or no males are

produced (one of the circumstances, according to Jordan, being season of

the year), and the females continue the species parthenogenetically. In

other cases, though males are produced they are in very small numbers. Some

species of Thysanoptera are never winged; in others the individuals are

winged or wingless according to sex. But there are other cases in which the

female is usually wingless, and is exceptionally winged. The winged

specimens in this case are, it is thought, of special use in disseminating

the species. Jordan has suggested that these phenomena may be of a regular

nature, but Uzel does not take this view. Another condition may be

mentioned, in which the species is usually wingless, but winged individuals

of the male as well as of the female sex occasionally appear. _Thrips lini_

apparently makes regular migrations, feeding at one time underground on the

roots of flax, and then changing to a life in the open air on other plants.

Numerous forms of Thysanoptera, belonging to both of the great divisions of

the Order, have been found fossil in Europe and North America, but all are

confined to deposits of the Tertiary epoch.

Of the 135 species known to Uzel, 117 are European; they are divided into

two Sub-Orders. 1, Terebrantia, in which the females are provided with an

external toothed ovipositor, of two valves; 2, Tubulifera, in which there

is no ovipositor, and the extremity of the body is tubular in both sexes.

The British species are about 50 in number, and were described by Haliday

about 60 years ago;[461] of late they have been very little studied.

The name Physopoda or Physapoda is used for this Order, instead of

Thysanoptera, by several naturalists.

{532}CHAPTER VIII

HEMIPTERA—OR BUGS

ORDER IX. HEMIPTERA.

_Mouth consisting of a proboscis or mobile beak (usually concealed by

being bent under the body), appearing as a transversly-jointed rod or

grooved sheath, in which are enclosed long slender setae (like

horse-hairs). Wings (nearly always) four; the anterior frequently more

horny than the posterior pair, and folding flat on the back, their apical

portions usually more membranous than the base_ (Heteroptera); _or the

four wings may cover the abdomen in a roof-like manner, and those of the

anterior pair may not have the basal and apical parts of different

consistences_ (Homoptera); _sometimes all four of the wings are

transparent. The young resembles the adult in general form; the wings are

developed outside the body, by growth, at the moults, of the sides of the

hinder portions of the meso- and meta-notum; the metanotal prolongations

being more or less concealed by the mesonotal._

The Hemiptera or Bugs are perhaps more widely known as Rhynchota. In

deciding whether an Insect belongs to this Order the student will do well

to examine in the first place the beak, treating the wings as subordinate

in importance, their condition being much more variable than that of the

beak. The above definition includes no reference to the degraded Anoplura

or Lice. These are separately dealt with on p. 599; they are absolutely

wingless, and have an unjointed proboscis not placed beneath the body, the

greater part of it being usually withdrawn inside the body of the Insect.

The Hemiptera are without exception sucking Insects, and {533}the

mouth-organs of the individual are of one form throughout its life. In this

latter fact, coupled with another, that the young are not definitely

different in form from the adult, Bugs differ widely from all other Insects

with sucking-mouth. They agree with the Orthoptera in the facts that the

mouth does not change its structure during the individual life, and that

the development of the individual is gradual, its form, as a rule, changing

but little. In respect of the structure of the mouth, Orthoptera and

Hemiptera are the most different of all the Orders. Hence, Hemiptera is

really the most isolated of all the Orders of Insects. We shall

subsequently see that, like Orthoptera, the Order appeared in the

Palaeozoic epoch. Although a very extensive Order, Hemiptera have for some

incomprehensible reason never been favourite objects of study. Sixty years

ago Dufour pointed out that they were the most neglected of all the great

Orders of Insects, and this is still true; our acquaintance with their

life-histories and morphology especially being very limited.

[Illustration: Fig. 255—_Eusthenes pratti_ (Pentatomidae). China. A, Nymph:

_a_, case of anterior, _b_, of posterior wing; _c_, orifices of

stink-glands; B, the adult Insect.]

There is probably no Order of Insects that is so directly connected with

the welfare of the human race as the Hemiptera; indeed, if anything were to

exterminate the enemies of Hemiptera, we ourselves should probably be

starved in the course of a few months. The operations of Hemiptera,

however, to a large extent escape observation, as their mouth-setae make

merely pricks that do not attract notice in plants; hence, it is probable

that {534}injuries really due to Hemiptera are frequently attributed to

other causes.

In the course of the following brief sketch of the anatomy and development

of Hemiptera, we shall frequently have to use the terms Heteroptera and

Homoptera; we may therefore here mention that there are two great divisions

of Hemiptera having but little connection, and known by the above names:

the members of these two Sub-Orders may in most cases be distinguished by

the condition of the wings, as mentioned in the definition at the

commencement of this chapter.

EXTERNAL STRUCTURE.—The mouth-parts consist of an anterior or upper and a

posterior or lower enwrapping part, and of the organs proper, which are

four hair-like bodies, dilated at their bases and resting on a complex

chitinous framework. The lower part forms by far the larger portion of the

sheath and is of very diverse lengths, and from one to four-jointed: it is

as it were an enwrapping organ, and a groove may be seen running along it,

in addition to the evident cross-segmentation. The upper covering part is

much smaller, and only fills a gap at the base of the sheath; it can

readily be lifted so as to disclose the setae; these latter organs are

fine, flexible, closely connected, rods, four in number, though often

seeming to be only three, owing to the intimate union of the components of

one of the two pairs; at their base the setae become broader, and are

closely connected with some of the loops of the chitinous framework that is

contained within the head. Sometimes the setae are much longer than the

sheath; they are capable of protrusion. Although varying considerably in

minor points, such as the lengths of the sheath and setae, and the number

of cross-joints of the sheath, these structures are so far as is known

constant throughout the Order. There are no palpi, and the only additions

exceptionally present are a pair of small plates that in certain forms

(aquatic family Belostomidae) lie on the front of the proboscis near the

tip, overlapping, in fact, the last of the cross-articulations.

Simple as is this system of trophi its morphology is uncertain, and has

given rise to much difference of interpretation. It may be granted that the

two portions of the sheath are respectively upper lip, and labium; but as

to the other parts wide difference of opinion still prevails. On the whole

the view most generally accepted, to the effect that the inner pair of the

setae correspond {535}in a broad sense with maxillae of mandibulate

Insects, and the outer pair with mandibles, is probably correct. Mecznikow,

who studied the embryology,[462] supports this view for Heteroptera, but he

says (_t.c._ p. 462), that in Homoptera the parts of the embryo

corresponding with rudimentary maxillae and mandibles disappear, and that

the setae are subsequently produced from peculiar special bodies that are

at first of a retort-shaped form; the neck of the retort becoming

afterwards more elongate to form the seta; also that in the Heteropterous

genus _Gerris_ the embryology in general resembles that of Homoptera, but

the development of the setae is like that of other Heteroptera (_t.c._ p.

478). This discontinuity in the development of the Homopterous mouth has

since been refuted by Witlaczil,[463] who found that the retort-shaped

bodies really arise from the primary segmental appendages after they have

sunk into the head. We are therefore justified in concluding that the

mouth-parts are at first similarly developed in all Hemiptera, and that

this development is of a very peculiar nature.

[Illustration: Fig. 256—Mouth-parts of Hemiptera. (After Wedde.) A, Section

of the head and proboscis of _Pyrrhocoris apterus_: _dr_, gland; _i.g_,

infra-oesophageal ganglion; _lb_, labium; _lr_, labrum; _m_, muscles; _m_^1

muscle (depressor of labium); _m_^2, muscle of syringe; _ph_, pharynx; _s_,

setae; _s.g_, supra-oesophageal ganglion; _sp. dr_, salivary gland; _spr_,

syringe: B, transverse section of proboscis of _Pentatoma rufipes_, at

third joint of sheath: _m_, _m_, muscles; _md_, mandibular seta; _mx_,

maxillary setae; _n_, nerve; _p_, the sheath or labium; _tr_, trachea.]

Smith is convinced that there are no traces of mandibular structure in any

Hemiptera.[464] On the other hand, numerous entomologists have supposed

they could homologise satisfactorily various parts of the Hemipterous

trophi with special parts of the {536}maxillae and labium of mandibulate

Insects. This point has recently been discussed by Marlatt[465] and by

Heymons.[466] From the latter we gather that the mode of growth is peculiar

by the extension backwards of some of the sclerites, and their becoming

confounded with parts of the wall of the head. From all this it appears

that at present we cannot correctly go farther than saying that the trophi

of Hemiptera are the appendages of three head-segments, like those of other

Insects. The views of Savigny, Léon,[467] and others to the effect that

labial palpi, and even other parts of the labium of Mandibulata can be

satisfactorily identified are not confirmed by Heymons.

Underneath the pharynx, in the head, there is a peculiar structure for

which we have as yet no English term. It was apparently discovered by

Landois and Paul Mayer,[468] and has been called "Wanzenspritze," which we

translate as syringe. It may be briefly described as a chamber, into which

the salivary ducts open, prolonged in front to the neighbourhood of the

grooves of the setae in the rostrum; behind, it is connected with muscles;

it has no direct connection with the pharynx, and though it was formerly

supposed to be an organ of suction, it seems more probable that it is of

the nature of a force-pump, to propel the products of some of the bug's

glands towards the tips of the setae.

The rostrum being extended from its position of repose, the tip of the

sheath is brought into contact with the object to be pierced, the surface

of which is probably examined by means of sensitive hairs at the extremity

of the sheath; these therefore functionally replace to some extent the

palpi of other Insects. As a rule the sheath does not penetrate (though

there is reason for believing that in various of the animal-feeding bugs it

does so), but the setae are brought into action for piercing the skin of

the plant; they are extremely sharp, and the outer pair are usually barbed,

so that when once introduced a hold is easily maintained. This being

established it is thought that the salivary pump comes into play, and that

a fluid is injected into the object pierced so as to give rise to

irritation or congestion, and thus keep up a supply of fluid at the point

operated on: this fluid extends along the grooved setae by capillary

attraction, and the {537}rapidity of the current is increased by a pumping

action of the pharynx, and possibly by movements of the setae themselves.

Though the setae are often extremely elongate—sometimes several times the

length of the body—they are nearly always slender, and there is no reason

to suppose that a perfect, or air-tight, tube is formed; hence it is

probable that capillary attraction is really the chief agent in the

ingestion of the fluid. The slight diversity of structure of the

Hemipterous trophi is in very striking contrast with what we find in

mandibulate Insects, and in the less purely suctorial Insects, such as

Diptera and some divisions of Hymenoptera. Schiödte in commenting on this

has suggested that it is probably due to the small variety of actions the

rostrum is put to.[469]

[Illustration: Fig. 257—_Saccoderes tuberculatus_ Gray. Brazil. (Fam.

Reduviidae.) (Antennae absent in the specimen represented.)]

The head exhibits great variety of form; in the Homoptera the front part is

deflexed and inflexed, so that it is placed on the under surface, and its

anterior margin is directed backwards; it is often peculiarly inflated; in

the Lantern-flies or Fulgoridae (Fig. 282) to an incomprehensible extent.

In the great Water-bugs, Belostomidae, there is on the under surface a deep

pocket for each antenna, beautifully adapted to the shape of the

curiously-formed appendage (Fig. 279). The prothorax is always very

distinct, frequently large, and in many of the Heteroptera (Fig. 257), as

well as in the Homopterous family, Membracidae (Fig. 283), assumes the most

extraordinary shapes. Both meso- and meta-thorax are well developed. The

former is remarkable for the great size of the scutellum; in some cases

(Plataspides, Scutellerides) this forms a large process, {538}that entirely

covers and conceals the alar organs, so that the Insect has all the

appearance of being apterous. The exact composition of the abdomen has not

been satisfactorily determined, opinions varying as to whether the segments

are nine, ten, or eleven in number. The difficulty of determining the point

is due to two facts: viz. the extreme modification of the terminal segments

in connection with the genital appendages, and the prominence of the

extremity of the alimentary canal. If this terminal projection is to be

treated as a segment, it would appear that eleven segments exist, at any

rate in some cases; as the writer has counted ten distinct segments in a

young Coreid bug, in addition to the terminal tube. This tube in some of

the male Heteroptera is very subject to curious modifications, and has been

called the rectal cauda. Verhoeff considers that ten segments were

invariably present in the females examined by him in various families of

Heteroptera and Homoptera.[470] In Aphidae (a division of Homoptera),

Balbiani considers there are eleven abdominal segments present; but he

treats as a segment a projection, called the cauda, situate over the anus;

this structure does not appear to be homologous with the rectal cauda we

have just mentioned. In Coccidae the number of abdominal segments is

apparently reduced. Schiödte states[471] that the older authorities are

correct in respect of the stigmata; there are, he says, in Heteroptera

invariably ten pairs; one for each thoracic segment; and seven abdominal,

placed on the ventral face of the pleural fold of the abdomen. In some

cases there are additional orifices on the external surface that have been

taken for stigmata, though they are really orifices of odoriferous glands;

these openings may exist on the metasterna or on the dorsal surface of the

abdomen. The lateral margins of the abdomen are frequently greatly

developed in Heteroptera, and are called "connexivum;" the upper and lower

surfaces of the body meeting together far within the marginal outline. Dr

Anton Dohrn many years ago[472] called attention to the extremely

remarkable structure of the terminal segments in many male Hemiptera; and

the subject has been subsequently very imperfectly treated by the present

writer and other entomologists, but it has never received the attention it

deserves.

{539}In the females of numerous Heteroptera and Homoptera (Capsidae,

Cicadidae, etc.) there is a well-developed ovipositor, that serves both as

a cutting instrument to make slits in the stems of plants, and as a

director to introduce the eggs therein. Verhoeff considers that it always

consists of two pairs of processes (though one pair may be very small), one

from the eighth abdominal segment, the other from the ninth.[473]

The antennae usually have very few joints, often as few as four or five,

their maximum number of about twenty-five being attained in the males of

some Coccidae, this condition being, however, present in but few of even

this family. In _Belostoma_ (Fig. 279) they assume extremely curious forms,

analogous to what we find in the Coleopterous genus _Hydrophilus_. In

addition to the compound eyes, there are usually ocelli, either two or

three in number, but wanting in many cases. The usual number of joints of

the tarsi is three, but in Coccidae there is only one joint.

[Illustration: Fig. 258.—Alar organs of a Capsid bug (_Capsus laniarius_).

A, Elytron: A, clavus; B, corium; C, cuneus; D, membrane; E, E, cell of the

membrane; B, hind-wing.]

The wings (Fig. 258) exhibit much diversity. The anterior pair usually

differ greatly from the posterior; they are called elytra, hemi-elytra or

tegmina. This difference in the two pairs is the rule in the first of the

great divisions of the Order, and the name Heteroptera is derived from the

fact. In this Sub-Order the front wings close over the back, and are more

or less horny, the apical part being, however, membranous. Systematists

make use of the wings for the purpose of classification in Heteroptera, and

distinguish the following parts, "clavus," "corium," "membrane," the corium

being the larger horny division, the clavus the part lying next the

scutellum and frequently very sharply distinguished from the corium; the

membrane is the apical part. The outer or costal part of the wing is also

often sharply delimited, and is called the "embolium;" in the great family

Capsidae and a few others, the outer apical part of the {540}corium is

differentiated from the rest of the surface, and is termed the "cuneus." In

Plataspides, one of the divisions in which the alar organs are entirely

covered by the scutellum, they are modified in a very remarkable manner. In

the Homoptera the divisions named above do not exist, and the wings in

repose are placed in a different position, as stated in our definition of

the Order. It is said to be very difficult to homologise the wing-nervures

of Hemiptera, and nothing appears to be known as to the mode of their

development.

The alar organs in Hemiptera exhibit a very frequent form of variation

within the limits of the same species; this has not yet been

elucidated.[474] In some cases in the Heteroptera nearly all the

individuals of a generation may have the wings aborted; sometimes this

occurs as a local variation. In Aphidae the occurrence of winged and

wingless individuals is very common, and has even become an important

factor in their extraordinary life cycles. (See _Chermes_, etc.,

subsequently.)

INTERNAL ANATOMY.—The alimentary canal presents considerable diversity and

some remarkable features. There is a slender tube-like oesophagus and a

large crop. It is difficult to assign any of the parts posterior to this to

the divisions usual in other Insects, and it is said that the distinction

of parts histologically is as vague as it is anatomically. In the

Heteroptera the Malpighian tubes open into two (or one) vesicular

dilatations seated immediately in front of the short rectum: between this

point and the crop there may be a very elongate, slender portion with one

or more dilatations, these parts apparently replacing the true or chylific

stomach. There is no gizzard. In the Homoptera the relations of the

divisions of the alimentary canal are even more puzzling; the canal is

elongated and forms coils, and these are connected with tissues and tunics

so as to make their dissection extremely difficult. List says that there

are great differences in the alimentary canal among the members of the one

family Coccidae. There are usually four Malpighian tubes, but in Coccidae

there is only one pair, and in Aphidae none. The excretory cells of these

tubes are in Hemiptera of remarkably large size. There is a large

development of salivary glands, at least two pairs existing. There can be

little doubt that some of their products are used for purposes of

injection, as {541}already described, though Künckel came to the conclusion

that the saliva when placed in living plants is totally innocuous.[475]

The ganglia of the nervous system are all concentrated in the thorax and

head. In some cases (in various Homoptera) the infra-oesophageal ganglion

is placed at a distance from the supra-oesophageal ganglion, and may even

be united with the thoracic mass of ganglia (_Orthezia_, etc.); in this

case the chitinous framework of the mouth-parts is interposed between the

supra- and the infra-oesophageal ganglia. In _Pentatoma_ all the three

ganglionic masses are brought into close proximity, but in _Nepa_ the

thoracic mass of ganglia and the infra-oesophageal ganglion are widely

separated.

The ovarian tubes vary greatly in number: according to List in _Orthezia

cataphracta_ the number differs considerably in different individuals, and

even in the two ovaries of the same individual, the number being usually

two. The testes are not placed in a common tunic, though they are

frequently approximated or even contiguous.[476]

The smell of bugs is notorious. In many species it is not unpleasant,

though as a rule it is decidedly offensive. It is a remarkable fact that

the structures connected with the production of this odour are different in

many cases in the young and in the adult. The odour emitted by the latter

proceeds from a sac seated at the base of the abdomen, and opening

exteriorly by means of an orifice on each side of the metasternum; while in

the young there are two glands situated more dorsally and a little more

backwards, and opening on two of the dorsal plates of the abdomen (Fig.

255, A).[477] In the young the dorsum of the abdomen, where the

stink-glands open, is exposed, but this part in the adult is covered by the

wings. The odorific apparatus is specially characteristic of Heteroptera,

and Künckel states that there is so much variety that generic and even

specific characters might be drawn from conditions of the stink-glands. As

a rule they are most constantly present in the plant-feeding forms; in some

essentially carnivorous forms (Reduviidae, Nepidae, {542}Notonectidae) they

are entirely absent. The offensive matter emitted by _Notonecta_ is of a

different nature, and is probably anal in origin.

METAMORPHOSIS OR POSTEMBRYONIC DEVELOPMENT.—In the language of the

systematists of metamorphosis, Hemiptera are said to be Homomorpha

Paurometabola—that is, the young differ but little from the adult.

According to Brauer's generalisations they are Menorhynchous,

Oligonephrous, Pterygogenea, _i.e._ they have a sucking mouth that does not

change during life, few Malpighian tubes, and are winged in the adult

state. It is generally admitted that the Homoptera do not completely agree

with Heteroptera in respect of the metamorphosis, it being more marked in

the former, and in Coccidae attaining (as we shall mention when discussing

that family) nearly if not quite the condition of complete metamorphosis of

a peculiar kind. Unfortunately we are in almost complete ignorance as to

the details of the life-histories and development of Heteroptera, so that

we can form no generalised opinion as to what the post-embryonic

development really is in them, but there are grounds for supposing that

considerable changes take place, and that these are chiefly concentrated on

the last ecdysis. The young of some bugs bear but little resemblance to the

adult; the magnificently-coloured species of _Eusthenes_ (Fig. 255), before

they attain the adult condition are flat, colourless objects, almost as

thin as a playing-card; it is well known that the extraordinary structures

that cover and conceal the body in Plataspides, Scutellerides, Membracides,

etc., are developed almost entirely at the last moult: it is not so well

known that some of these changes occur with much rapidity. A very

interesting account of the processes of colour-change, as occurring in

_Poecilocapsus lineatus_ at the last ecdysis, has been given by

Lintner,[478] and from this it appears that the characteristic coloration

of the imago is entirely developed in the course of about two hours,

forming a parallel in this respect with Odonata. When we come to deal with

Aphidae we shall describe the most complex examples of cycles of

generations that exist in the whole of the animal kingdom.

FOSSIL HEMIPTERA.—Hemiptera are believed to have existed in the Palaeozoic

epoch, but the fossils are not numerous, and opinions differ concerning

them. _Eugereon hockingi_, a {543}Permian fossil, was formerly supposed to

be a Homopterous Insect, but it is very anomalous, and its claim to a

position in Hemiptera is denied by Brauer,[479] who considers it to be

Orthopterous. It is now generally recognised that this fossil requires

complete reconsideration. Another Permian fossil, _Fulgorina_, is admitted

to be Homopterous by Scudder, Brauer and Brongniart. Scudder thinks the

Carboniferous _Phthanocoris_ was an Archaic Heteropterous Insect, and if

correct this would demonstrate that both of the two great Sub-Orders of

Hemiptera existed in Palaeozoic times. Brauer, however, is inclined to

refer this fossil to Homoptera, and Brongniart[480] speaks of it as being

without doubt a Fulgorid. _Dictyocicada_, _Rhipidioptera_ and

_Meganostoma_, from the Carboniferous shales of Commentry, have also been

referred to Fulgoridae by Brongniart, but the evidence of their alliance

with this group is far from satisfactory. In the Secondary epoch numerous

Hemiptera existed, and are referred to several of the existing families.

They come chiefly from the Oolite. In the Eocene of the Isle of Wight a

fossil has been discovered that is referred to the existing Homopterous

genus _Triecphora_.

We are not entitled to conclude more from these facts than that Homoptera

probably appeared before Heteroptera, and date back as far as the

Carboniferous epoch.

CLASSIFICATION AND FAMILIES.—No complete catalogue of Hemiptera exists, but

one by M. Severin is in course of publication. It is probable that there

are about 18,000 species at present described, two-thirds of this number

being Heteroptera. In Britain we have about 430 species of Heteroptera and

600 of Homoptera. The classification of the Order is not in a very advanced

condition. The following table exhibits the views of Schiödte[481] in a

modified form:—

Front of head not touching the coxae. I. Heteroptera.

Front of head much inflexed so as to be in contact with the coxae.

II. Homoptera.

Sub-Order I. Heteroptera.

Posterior coxae nearly globose, partly embedded in cavities, and having

a rotatory movement. Mostly terrestrial forms. 1. Trochalopoda.

Posterior coxae not globose, larger, and not embedded; their articulation

with sternum almost hinge-like. Posterior aspect of hind femur usually

more or less modified for the reception of the tibia when closed on{544}

it: mostly aquatic forms. 2. Pagiopoda.

Division 1. Trochalopoda.

This division includes the majority of the families of Heteroptera—viz.

the whole of the terrestrial families except Saldidae, and it also

includes Nepidae, a family of water-bugs.

Division 2. Pagiopoda.

This includes the six purely aquatic families of Heteroptera, except

Nepidae, which appear to have very little connection with the other

aquatic bugs. The only terrestrial Insects included in the family are the

Saldidae; in these the femora are not modified as they are in the aquatic

forms. Hemiptera that live on the surface of water, not in the water, are

classed with the terrestrial species. With these exceptions this

arrangement agrees with that of GYMNOCERATA and CRYPTOCERATA as usually

adopted,[482] and therefore followed in the following pages. Schiödte's

characters, moreover, do not divide his two divisions at all sharply.

Sub-Order II. Homoptera.

Tarsi usually three-jointed Series Trimera.

" " two-jointed " Dimera.

" " of one joint " Monomera.

The classification of Homoptera is in a most unsatisfactory state;[483]

no two authors are agreed as to the families to be adopted in the series

Trimera. We have recognised only five—viz. Cicadidae, Fulgoridae,

Membracidae, Cercopidae, and Jassidae. The Dimera consists of Psyllidae,

Aphidae, Aleurodidae; and the Monomera of Coccidae only. It is usual to

associate the Dimera and Monomera together under the name of either

Phytophthires or Sternorhyncha, but no satisfactory definition can be

given of these larger groups, though it seems probable that the families

of which they are composed are natural and distinct.

Sub-Order I. HETEROPTERA.

SERIES 1. GYMNOCERATA.

The majority of the terrestrial families of Heteroptera form the series

Gymnocerata, in which the antennae are conspicuous, and can be moved about

freely in front of the head, while in {545}Cryptocerata they are hidden.

The series Gymnocerata includes all the terrestrial Heteroptera, and the

two families, Hebridae and Hydrometridae, which live on the surface of the

water or in very damp places; while Cryptocerata includes all the forms

that live under water.

[Illustration: Fig. 259—_Phloea corticata._ South America.]

FAM. 1. PENTATOMIDAE.—_Scutellum very large, at least half as long as the

abdomen, often covering the whole of the after-body and alar appendages.

Antennae often five-jointed. Proboscis-sheath four-jointed. Ocelli two.

Each tarsal claw with an appendage._—This, the largest and most important

family of the Heteroptera, includes upwards of 4000 species, and an immense

variety of forms. It is divided into no less than fourteen sub-families.

The species of one of these, Plataspides, are remarkable for their short,

broad forms, and the peculiar condition of the alar organs, which are so

completely concealed by the great scutellum that it is difficult to believe

the Insects are not entirely apterous. The head is usually inconspicuous

though broad, but in a few forms it is armed with horns. Though this

sub-family includes upwards of 200 species, and is very widely distributed

in the Old World, it has no representatives in America. The Scutellerides

also have the body covered by the scutellum, but their organs of flight are

less peculiar than they are in the Plataspides; the Insects of this

sub-family are highly remarkable on account of their varied and frequently

vivid coloration; some of them are metallic, and the colour of their

integuments differs greatly in some cases, according to whether the

specimen is wet or dry; hence the appearance after death is often very

different from that of the living specimen. These Insects are extremely

numerous in species. The sub-family Phloeides (Fig. 259), on the contrary,

includes only three or four South American species: they have no

resemblance at all to other Pentatomidae; they are flat, about an inch

long, and look like scales of bark, in this respect agreeing with _Ledra_

and some other Homoptera. The South American sub-family Cyrtocorides (Fig.

260) is of {546}equally small extent; the species are of strange irregular

shapes, for which we can find no reason. The Tessaratomides includes many

of the largest Hemiptera-Heteroptera, some of its members attaining two

inches in length.

The great family Pentatomidae, containing about 400 species, is represented

in Britain by about 36 native species, the most interesting of which are

perhaps those of the genus _Acanthosoma_. De Geer noticed long ago that the

female of _A. griseum_ exhibits great solicitude for its young, and his

statement has since been confirmed by Mr. Parfitt and the Rev. J. Hellins,

who found that the mother not only protects the eggs but also the young,

and that for a considerable time after hatching.[484]

[Illustration: Fig. 260—_Cyrtocoris monstrosus._ South America, × 3.]

Very little is known as to the life-histories of Pentatomidae. In some

cases the young are very different in appearance from the adults. The

peculiar great scutellum is not developed till the mature condition is

reached. But little attention has been given to the habits of Pentatomidae;

it is generally considered that they draw their nutriment from plants; the

American _Euthyrhynchus floridanus_ has, however, been noticed to suck the

honey-bee, and we think it probable that a good many Pentatomids will be

found to attack Insects.

The term Pentatomidae as applied to this family is of modern origin: in

most books the equivalent group is called Scutata, or Scutati, and the term

Pentatomidae is restricted in these works to the sub-family called

Pentatomides in the system we adopt.

FAM. 2. COREIDAE.—_Scutellum not reaching to the middle of the body;

proboscis-sheath four-jointed; ocelli present; antennae generally elongate

and four-jointed, inserted on the upper parts of the sides of the head;

femora not knobbed at the tip._—The members of this great family are easily

recognised by the above characters; formerly it was called Supericornia in

connection with the characteristic position of the antennae. About 1500

species are known, and they are arranged in no less than twenty-nine

sub-families. Many of them are Insects of large size, and they frequently

have a conspicuous disc, or dilatation, on one of the joints of the

antennae.

{547}[Illustration: Fig. 261.—_Diactor bilineatus._ South America. × 3/2.

Fig. 262—_Phyllomorpha laciniata_, carrying some of its eggs. Spain.]

Another very curious and, as yet, inexplicable peculiarity very commonly

met with among them, is that the hind legs may be of great size and

deformed; either the femora or the tibiae, or both, being very much

distorted or armed with projections. Brilliant colour is here comparatively

rare, the general tone being indefinite tints of browns, greys, or smoky

colours. The South American genus _Holymenia_ (_Copius_ of older authors)

consists of slender forms, having the elytra transparent even on the basal

part like Homoptera; this and some other peculiarities give the species of

this genus a certain resemblance to Insects of other Orders; Westwood says

that _Diateina holymenoides_ (Diptera) greatly resembles a bug of the genus

_Holymenia_. The tropical American genus _Diactor_ consists of a few

species of elegant colour having the hind legs very peculiarly shaped, the

tibiae being flattened and expanded in a sail-like manner, and ornamented

with agreeable colours different {548}from those on the rest of the body;

they are made more conspicuous by the femora being remarkably long and

thin; it is probable that they are used as ornaments. The subfamily

Phyllomorphides consists of about a dozen species, and is found in several

of the western parts of the Eastern hemisphere, one species, _P.

laciniata_, occurring in Southern Europe. This Insect is of very delicate

texture, and the sides of the body are directed upwards and deeply divided

so that a sort of basin is formed, of which the dorsum of the body is the

floor; the Insect is very spinose, and is thus enabled to carry its eggs,

the spines helping to retain them in position on the back. It is said to be

the male that thus carries the eggs. This species is able to stridulate,

and when doing so vibrates its antennae with excessive rapidity. We have

only about a score of species of Coreidae in Britain, and none of the

remarkable forms of the family are among them.

FAM. 3. BERYTIDAE.—_Very slender Insects with the first joint of the

antennae and the femora thickened at the tips._—This small family was not

distinguished from Coreidae by the older authors. It consists of about

fifty species, eight of which are found in Britain.

FAM. 4. LYGAEIDAE.—_The characters are the same as those mentioned for

Coreidae, except as regards the insertion of the antennae; the upper

surface or face of the head is not so flat, but is transversely convex, so

that seen in profile the antennae appear to be inserted well down on the

sides of the head._—The name Infericornia was formerly applied to these

Insects. They are on the average of smaller size than the members of the

Coreidae or Pentatomidae, and are much less conspicuous in colour and form;

a good many of the larger Lygaeids are, however, variegate with black,

yellow, and red. The family is very numerous in species, about 1400 being

known; they are arranged in thirteen sub-families; we have about sixty

species in Britain, nearly all small. _Eremocoris_ lives, when immature, in

the nests of the wood-ant, according to Wasmann. The family includes some

notorious Insect-pests. The Chinch-bug, _Blissus leucopterus_, commits very

serious ravages on corn and grasses in North America. The Cotton-stainer,

_Dysdercus suturellus_ is also very injurious to cotton in certain parts of

the New World: its growth has been described by Riley,[485] who thinks a

dye valuable for {549}commercial purposes might be procured from the

Insect. This bug has recently developed the habit of sucking oranges, and

has thus become injurious in Florida, as the fruit readily decays after it

has been punctured by these Insects. The phenomenon of "micropterism" is

exhibited by numerous Lygaeids, as well as by Pyrrhocoridae.

FAM. 5. PYRRHOCORIDAE.—_Distinguished from Lygaeidae only by the absence of

ocelli_, and not recognised as a distinct family by all Hemipterists. About

300 species are included. Our only British member is the notorious

_Pyrrhocoris apterus_; it is, however, very rare in this country, though it

abounds on the Continent, and has been the object of investigation by

embryologists and others. It displays in a most marked manner the curious

dimorphism as to the alar organs that is so common in certain divisions of

Hemiptera; the elytra and wings being sometimes normally developed, while

in other cases the wings are entirely absent, and the horny, basal part of

the elytra only is present. In some localities, and in some years, only the

micropterous form is found, while on other occasions there may be a large

percentage of the macropterous form. The abundance of this Insect has

enabled the French chemist Physalix to obtain an amount of its colouring

matter sufficient for analysis; as the result he procured a substance,

insoluble in water, very closely allied to carotine.[486] The Oriental

Insect _Lohita grandis_ is one of the most remarkable of Bugs, the male of

the Sumatran variety being over two inches in length, having enormously

long antennae, and the abdomen extended to about twice the normal length,

while the other sex is in the usual condition in these respects. The

species is said to be injurious to the cotton-plant in India.

FAM. 6. TINGIDAE.—_Tarsi two-jointed. Elytra more or less reticulate,

consisting of strong, irregular, thick lines forming a framework of cells,

the enclosed part of the cell being of different texture and frequently

transparent; antennae with terminal joint more or less knob-like, the

preceding joint very long; ocelli wanting; pronotum prolonged behind,

covering the scutellum; front coxae placed at the lack of the thorax._—This

is the first of a series of families with only two joints to the feet.

These little bugs are very remarkable objects, and exhibit much variety in

their peculiar {550}sculpture, which in numerous forms attains a condition

of elegance well worthy of attention. There are nearly 300 species known,

and in Britain we have about a score. The characters we have given above do

not apply to the genus _Piesma_, though it is usually placed in this

family; its scutellum is not covered, and ocelli are present. Although but

little is known as to the nature of the lives of Tingidae, yet it was

pointed out long ago by Réaumur that a species of the family (probably _C.

clavicorne_, Fig. 263), lives in deformations of the flowers of the Labiate

plant now called _Teucrium chamaedrys_; Frauenfeld has more recently

confirmed this observation, and shown that the closely allied _C. teucrii_

affects the flowers of _T. montanum_ in a similar manner.[487]

[Illustration: Fig. 263—_Copium clavicorne._ Europe. (After Rübsaamen.)]

[Illustration: Fig. 264—_Aradus orientalis._ Siam.]

FAM. 7. ARADIDAE.—_Very flat, broad; scutellum exposed, large or moderate;

abdomen broader than the alar organs, which it frequently encases like a

broad frame. Front coxae placed in the middle of the prosternum._—These

very flat Insects, of obscure colour, have frequently very peculiar

sculpture. They live under bark, or on fungi growing from bark, and are

supposed to draw their nutriment from the fungi, though but little is

actually known as to their natural history. The family is almost

cosmopolitan, and includes about 300 species, of which five occur in

England. The small sub-family Isoderminae consists of a few species that

are placed only provisionally in Aradidae; they differ from the normal

members by there being no groove on the {551}breast, so that the rostrum is

free. Of the five species, three occur in Chili and Patagonia, two in

Tasmania, and one in Australia.

FAM. 8. HEBRIDAE.—_Minute bugs, of semiaquatic habits, clothed beneath with

a dense, minute, silvery pubescence; antennae five-jointed; legs of not

more than average length; elytra in larger part membranous._—This small

family consists altogether of only about a dozen species; we have two

species of the genus _Hebrus_ in Britain; they are usually found in very

wet moss.

[Illustration: Fig. 265.—_Halobates sobrinus._ Under surface of a female

carrying eggs. Pacific Ocean (Marquesas).]

FAM. 9. HYDROMETRIDAE.—_Form very diverse; antennae four-jointed, tarsi

two-jointed. Coxae usually widely separated. Either wingless or with elytra

of one texture throughout, having no membranous part. Under surface with a

minute velvet-like pubescence. In many forms the legs are of great

length._—Although of comparatively small extent—scarcely 200 species being

at present known—this family is of great interest from the habit possessed

by its members of living on the surface of water. In the case of the

notorious genus _Halobates_ (Fig. 265) the Insects can even successfully

defy the terrors of Neptune and live on the ocean many hundreds of miles

from land. There is great variety of form among Hydrometridae. The European

and British genus _Mesovelia_ is of short form, and but little dissimilar

from ordinary land-bugs, with which, indeed, it is connected by means of

the genus _Hebrus_, already noticed. _Mesovelia_ represents the sub-family

Mesoveliides, which, though consisting of only four species, occurs in both

hemispheres, and in the tropics as well as in the temperate regions. Our

species, _M. furcata_, walks on the surface of the water, the movements of

its legs and the position of its coxae being those of land-bugs. Another

British Insect—the highly remarkable _Hydrometra stagnorum_—is of

excessively slender form, with long thin legs, by aid of which it

{552}walks on the surface-film of water, above which its body is held well

separated. It is easily drowned, and if submerged it has great difficulty

in escaping from the water. This genus represents the sub-family

Hydrometrides, and is apparently almost cosmopolitan. _Velia currens_ is

another common British Insect; it loves the eddies and currents of

backwaters on burns and streams, and is very abundant in Scotland. An

American ally, _Rhagovelia plumbea_, appears to be not uncommon on the

surface of the ocean in the Gulf of Mexico, near the shores. The great

majority of the family belong to the division Gerrides, of which the

curious, long Insects that float so lazily and skim so easily on the

surface of quiet streams are typical. The species of the genus now called

_Gerris_, but formerly known as _Hydrometra_ are apparently distributed all

over the world; we have ten in Britain. They have very long legs, and on

being alarmed move away with the greatest ease.

The genus _Halobates_ includes at present fifteen species. They are found

on the ocean, where the surface-water is warm, in various parts of the

world. They are destitute of any trace of alar organs, the meso- and

meta-thorax are closely united and large, while the abdomen is very small,

so that the body is of oval form; the middle legs are thrown so far back

that they are placed immediately over the posterior pair. When the sea is

calm these Insects skim over the surface with rapidity, but disappear as

soon as it becomes agitated. They are believed to feed on small animals

recently deceased; Witlaczil says on the juices of jelly-fish. The young

are frequently met with, and there can be no doubt that the whole

life-cycle may be passed through by the Insect far away from land. The

Italian ship _Vettor Pisani_ met with a bird's feather floating on the

ocean off the Galapagos Islands, covered with eggs which proved to be those

of _Halobates_ in an advanced stage of development. It was formerly

believed that the female carries the eggs for some time after their

exclusion, and although this has since been denied, it is nevertheless an

undoubted fact, for it was observed by Mr. J. J. Walker,[488] to whom we

are indebted for a specimen having the eggs still attached to the body, as

shown in Fig. 265. Mr. Walker believes the bugs shelter themselves when the

sea is at all rough by keeping at a sufficient distance {553}below the

surface; they can dive with facility, and are gregarious. They are

frequently found close to the shore, and Mr. Walker has even met with them

on land. The stink-glands of other Hemiptera are said by Nassonoff to be

replaced in _Halobates_ by peculiar ventral glands. An allied genus,

_Halobatodes_, was supposed to be oceanic, but this is not the case, some

of the species having been found recently in fresh water in India, and

others in estuaries at Port Darwin. A remarkable allied form, _Hermatobates

haddoni_, was recently discovered by Professor Haddon in Torres Straits.

Apart from the oceanic life, _Halobates_ is by no means the most

extraordinary of the Hydrometridae. The Javanese _Ptilomera laticaudata_

repeats some of its peculiarities, and is of larger size, with the sexes

very different. The most remarkable of the family is perhaps the

fresh-water genus _Rheumatobates_ (Fig. 266), in which the males have

peculiar prehensile antennae that look like legs. These curious Insects

inhabit North America and the West Indies.

[Illustration: Fig. 266—_Rheumatobates bergrothi._ × 10. West Indies.

(After Meinert.)]

We may here notice an enigmatic Insect called _Hemidiptera haeckeli_ by

Léon. From the single specimen known it is concluded that the Insect has

only one pair of wings, and that they are attached to the metathorax. It

is, however, possible, as {554}suggested by Bergroth,[489] that the

anterior pair have been detached by some accident.

FAM. 10. HENICOCEPHALIDAE.—_Head swollen behind the eyes so as to form a

sort of globe, on the anterior part of which the ocelli are placed. Rostrum

extremely short. Elytra rather large, of one consistence throughout;

conspicuously veined._—There is only one genus; it is very widely

distributed, about a dozen species being known; one of these occurs in the

south of Europe. These curious little bugs appear to be most nearly allied

to the Reduviidae. According to Westwood and others they are somewhat

gregarious; a Tasmanian species dances in the air after the fashion of

midges or May-flies, and dispenses an agreeable, musk-like odour.

[Illustration: Fig. 267—_Carcinocoris binghami_ (Phymatidae). Burma.]

FAM. 11. PHYMATIDAE.—_Front legs of peculiar structure, short and stout,

with long coxae, short thick femora, and tibiae curvate, pointed;

frequently without tarsi._—The Insects of this family are believed to be

predaceous, the structure of the legs being such as is called raptorial,

and one species, _Phymata erosa_, being known to capture and suck

honey-bees in North America. There are only about seventy species of

Phymatidae known. We have {555}none in Britain, though there are a few in

Southern Europe; one of these, _P. crassipes_, extends as far north as

Paris. The distinction of the family from Reduviidae is doubtful.[490]

There are a few very rare forms (Fig. 267) in which the front tibia is

articulated to the femur in such a way that a pair of pincers is formed:

the tarsus is in this form, as well as in some other Phymatidae, absent.

[Illustration: Fig. 268—_Ghilianella filiventris._ Brazil. A, the female

Insect. B, extremity of the body of the male.]

FAM. 12. REDUVIIDAE.—_Head more or less elongate, very movable, eyes placed

much in front of the thorax, ocelli, when present, behind the eyes.

Proboscis short, or moderately short, not extending on to the breast, in

repose curved under the head so as to form a loop therewith. Elytra, when

present, consisting of three divisions. Tarsi three-jointed._—This is one

of the largest and most important families of Hemiptera. Upwards of 2000

species are already known; the habits seem to be chiefly of a predaceous

nature, the creatures drawing their nutriment from the animal rather than

from the vegetable kingdom, and their chief prey being in all probability

other kinds of Insects. There is, perhaps, no family of Insects exhibiting

a greater variety of form and colour. The Emesids are amongst the most

delicate of Insects, equalling in this respect the {556}daddy-long-leg

flies; they are, however, highly predaceous; their front legs are

peculiarly formed for capturing and holding their prey, and have long

coxae, like _Mantis_, so that these Insects are commonly mistaken for small

or young Mantises, from which their sucking proboscis at once distinguishes

them. This curious starved-looking form of bug reaches its maximum of

peculiarity in the South American genus _Ghilianella_ (Fig. 268). According

to Pascoe the linear form enables the young larva to be carried about by

the mother, the long slender abdomen of the larva being curled around the

thorax of the parent. _Ploiaria pallida_, from Woodlark Island, is an

Insect of excessive fragility and elegance, with the long thin legs

coloured with alternate patches of black on a white ground, giving rise to

a very curious appearance remarkably analogous to what we find in some of

the equally delicate daddy-long-leg flies.

[Illustration: Fig. 269—_Nabis lativentris_, young. Cambridge. A, Insect

seen from above; B, profile.]

We have three species of Emesides in Britain, but most of our Reduviidae

belong to the sub-family Nabides. These approximate to ordinary bugs in

appearance and characters more than do any other of the Reduviidae. One of

our indigenous Nabides is of great interest from the curious resemblance it

has to an ant (Fig. 269). The likeness is brought about by the sides of the

base of the abdomen being very pallid in colour, except a dark mark in the

middle; this mark is in shape like the pedicel of an ant. Viewed in profile

it is found that on the base of the abdomen there is an elevation like the

"scale" in this position in {557}ants, and that the abdomen is extremely

ant-like in form. This resemblance is quite parallel with that of an

Orthopteron to an ant (see Vol. V. p. 323); the Insect is by no means

uncommon, and it is strange that this curious case of resemblance should

hitherto have escaped notice. The bug runs about on plants and flowers, and

is frequently in company with ants, but we do not know whether it preys on

them. Not the least remarkable of the facts connected with this Insect is

that the resemblance is confined to the earlier instars; the adult bug not

being like an ant. We may here mention that there are numerous bugs that

closely resemble ants, and that on the whole there is reason to believe

that the resembling forms are actually associated during life, though we

really know very little as to this last point.

[Illustration: Fig. 270—_Ptilocnemus sidnicus._ Australia. (After Mayr.)]

[Illustration: Fig. 271—_Myiodocha tipulina._ China.]

The little sub-family Holoptilides, with twenty-five species, but widely

distributed in the Eastern hemisphere, is remarkable on account of the

feathered {558}antennae and legs of its members (Fig. 270). Altogether

fourteen sub-families are recognised, the most extensive one being

Harpactorides, including a great variety of remarkable forms; in the South

American genus _Notocyrtus_ (better known as _Saccoderes_, Fig. 257), the

prothorax is swollen and covers the body to a greater or less extent in the

fashion of a hood. In _Yolinus_ and _Eulyes_ the coloration is the most

conspicuous system that could be devised, the sides of the abdomen

(connexivum) being expanded into bright-red lobes on which are placed

patches of polished-black. The most remarkable form of Reduviid is,

perhaps, one from China (Fig. 271) of considerable size, of great

fragility, and greatly resembling, like some Emesides, a daddy-long-legs

fly, though it does not belong to the Emesides. It is an altogether

anomalous form. According to Seitz there is found on the Corcovado in

Brazil a Reduviid that exactly resembles one of the dark stinging-wasps of

the genus _Pepsis_, and the bug makes the same sort of movements as the

wasp does, though these are of a kind quite different from those of

ordinary bugs.[491]

[Illustration: Fig. 272—Eggs of _Endochus cingalensis_. "The eggs are

attached to a leaf and to each other by a viscid substance; eggs red, the

cover pale yellow, with the club white at the tip."—MS. note of E. E.

Green.]

Although the attacks of Reduviidae on animals are usually confined to the

smaller and more defenceless kinds, yet this is by no means invariably the

case; there are in fact numerous species that do not hesitate to attack man

himself. Several species of _Reduvius_ do this in Southern Europe, and are

frequently met with in houses. _R. personatus_ is the only species of the

genus in England; though far from common anywhere, it is sometimes found in

houses, and is said to destroy the common bed-bug; it is able to pass its

whole existence in our habitations, for the young are found as frequently

as the adult, and are usually concealed by a quantity of dusty matter, or

refuse, adhering to the body. This habit of covering the body with some

foreign substance is natural to the Insect, the young that are found on

trees being covered with matter derived therefrom. Darwin has given us an

account of {559}the Benchucha,[492] a bug an inch long, which in South

America attacks human beings after the fashion of the common bed-bug. In

this case no ill-effects follow the attack, but in the case of _Conorhinus

sanguisuga_ in Arizona, great pain and inflammation ensue and may end in

the gathering and discharge of pus.

Not the least remarkable of characters of _Reduviidae_ is the form of the

eggs of some of the species (Fig. 272, and Vol. V. Fig. 78, C); the egg

bearing a peculiar operculum, the purpose of which is at present quite

mysterious.

FAM. 13. AËPOPHILIDAE.—A single species forms this family. It is of

considerable interest, as it is incapable of flight, passing a large part

of its life covered by the sea. _Aëpophilus bonnairei is a small Insect

with quite short head, without ocelli, and with the organs of flight

represented by a pair of very short elytra, with rounded hind-margins._ It

is found on the shores of Western France, and, as a great rarity, on our

own south coast. It no doubt sucks small soft animals. In the Channel

Islands it occurs in spots where it is nearly always covered by a

considerable depth of water.

FAM. 14. CERATOCOMBIDAE.—_Minute bugs with ocelli and elytra. Rostrum free.

Head not broad, somewhat prolonged in front; eyes close to the thorax.

Elytra usually without a distinctly separated membrane. Tarsi

three-jointed._—This family includes at present only a few, minute, fragile

bugs, that have often been classified with Cimicidae or Anthocoridae. We

have only two British species, one of which, _Dipsocoris alienus_, is

common amongst the damp shingle at the margins of the burns and waters of

Scotland.

FAM. 15. CIMICIDAE.—_Ocelli absent; elytra very short and broad, so that

the broad abdomen is left uncovered. Head short and broad. Rostrum received

in a groove beneath the head. Tarsi three-jointed._—Although this family

consists of only a dozen species, it is the most notorious of all the

Order, as it includes the detestable _Cimex lectularius_ or common Bed-bug.

This Insect is now peculiar to the habitations of man, and is said not to

trouble savage races; or rather it is supposed to be present only when the

habitations have a certain degree of comfort and permanence. It has no

fixed period of the year for its development, but the generations succeed

one another so long as the temperature {560}is sufficiently elevated;

during too cold weather the Insects merely become stupefied, their lives

being as it were interrupted till warmth returns. It is a favourite food

with other Insects, and is destroyed by cockroaches and ants as well as by

_Reduvius_; the small black ant _Monomorium_ will, it is said, clear a

house of the bed-bug in a few days. Nothing is really known as to the

origin of this Insect; it is now very widely distributed. The other species

of the family frequent birds and bats, and are very similar to the common

bug. The genus to which the bed-bug belongs is in many works called

_Acanthia_ instead of _Cimex_. Other authors apply the term _Acanthia_ to

_Salda_, but it is better to allow the name _Acanthia_ to fall into disuse.

FAM. 16. ANTHOCORIDAE.—_Minute bugs, usually with ocelli and with elytra;

the latter occasionally abbreviated, but usually fully developed, with

membranous tip. Head prolonged in the middle in front much beyond the

insertion of the antennae; eyes not far from the thorax. Rostrum

free._—These small and obscure Insects appear to be rather numerous in

species, and to be chiefly connected with woods and forests. Some of the

species live in ants' nests. We have 27 British species belonging to 11

genera. About 200 species of the family are known. The members of the

sub-family Microphysides are remarkable from the great dissimilarity of the

sexes, for which it is not possible to assign any reason.

[Illustration: Fig. 273—_Polyctenes fumarius._ (After Westwood.)]

FAM. 17. POLYCTENIDAE.—_Proboscis-sheath three-jointed, tarsi four-jointed,

antennae four-jointed. Tegmina quite short, of one consistence._—The four

or five anomalous species forming this family are parasites on bats of the

genus _Molossus_, and have been found in both the Eastern and Western

hemispheres. Westwood, who first described {561}them,[493] treated them as

aberrant Anoplura or Lice, but there do not appear to be any sufficient

grounds for removing these parasites from Hemiptera-Heteroptera. The

condition of their alar organs reminds one of what exists in _Cimex_ and

_Aëpophilus_, and the mouth is not known to possess any very peculiar

structure. We have had no opportunity of making a thorough examination of

_Polyctenes_, and therefore speak with some diffidence.

[Illustration: Fig. 274—_Helopeltis_ sp. East India.]

[Illustration: Fig. 275—Section of a stem with egg of a Capsid bug allied

to _Helopeltis_ (Moesa-blight). × 58. (After Dudgeon.)]

FAM. 18. CAPSIDAE.—_Moderate-sized or small bugs, of delicate consistence,

without ocelli; the elytra and wings usually large in proportion to the

body, the former with two cells (occasionally only one) in the membrane.

Antennae four-jointed, the second joint usually very long, the terminal two

more slender than the others. The proboscis not received in a groove.

Scutellum exposed, moderately large. Tarsi three-jointed. Female with an

ovipositor capable of exsertion._—This family is one of the most extensive

of the Hemiptera; we have about 170 species in Britain, where they are most

abundant in the south. The exotic species have been but little collected.

Their colours are usually delicate rather than vivid, and are never

metallic. They frequent plants of all kinds, and many of them skip by the

aid of their wings with great agility in the sunshine. The majority

probably suck the juices of the plants, but some are known to prey on other

Insects. The species of the Indian genus _Helopeltis_ (Fig. 274) are

remarkable by possessing a knobbed spine projecting straight up from the

scutellum, making the individual look as if it were a specimen with a pin

through {562}it: they attack the tea-plant and do considerable damage. They

are known as Mosquito-blight. The egg is of comparatively large size, and

is placed by the bug in the stems of the tea-plant, but attached to one end

of the egg are two long slender threads that project externally. A similar

egg (Fig. 275) and method of oviposition have been described by Mr. Dudgeon

as occurring in another species of Capsidae, called Moesa-blight, in

India.[494]

FAM. 19. SALDIDAE.—_Head short and broad, with large, prominent eyes.

Ocelli present. Proboscis not applied to under surface of head or breast in

repose. Scutellum large, not covered. Elytra covering the upper surface of

the abdomen, formed of three distinct parts. Tarsi three-jointed._—These

little bugs run with velocity over mud in damp places, or live in wet moss;

some of them can jump; they are all of dark or obscure colour. There are

only three genera: _Salda_, of which we have numerous British species,

being the principal one.

SERIES 2. CRYPTOCERATA.

The remaining families of Heteroptera are of aquatic habits, and form in

nearly all works a separate division called Hemiptera Cryptocerata (or

Hydrocorisae, or Hydrocores), distinguished by the antennae being

apparently absent; they are, however, really present, being situate on the

under side of the head, to which they are closely pressed, or in some cases

placed in a pocket in front of each eye. There are six of these families.

Schiödte is doubtless correct in treating this division as an unnatural

one; it is, however, generally adopted, and is convenient for the purposes

of nomenclature and arrangement.

FAM. 20. GALGULIDAE or PELOGONIDAE.—_Form short and broad; head very broad,

with prominent eyes, ocelli present. Hind legs thin, formed for

running._—The Insects of this family are but little known; they are only

sub-aquatic in habits, frequenting damp places at the margins of streams

and waters. The presence of ocelli distinguishes them from other

water-bugs, with which indeed the Galgulidae appear to be but little

related. There are only about twenty species of the family known. We

possess none in Britain; but one, _Pelogonus marginatus_, occurs {563}in

South Europe. The other members of the family are very widely scattered

over the surface of the earth.

FAM. 21. NEPIDAE.—_Abdomen furnished behind with a long slender siphon;

front legs more or less elongate for capturing prey, placed quite at the

front edge of the prothorax._—This family consists of two interesting but

very dissimilar genera, _Nepa_ and _Ranatra_. Both are widely distributed

over the earth, and are rather numerous in species.[495] We have one

species of each genus in Britain. _Nepa cinerea_, the common

"water-scorpion," is one of the commonest of Insects in Southern Britain,

living concealed in shallow waters when nearly or quite stagnant. _Ranatra

linearis_ (Fig. 276) is much less common, and appears to be getting rarer;

it is not recorded from farther north than Cambridge.

[Illustration: Fig. 276.—_Ranatra linearis_, with the two portions, _a_, of

the respiratory siphon separated. Cambridge.]

The nature of the respiratory arrangements in these Insects is of

considerable interest; the long tube at the extremity of the body consists

of two parts (as shown in Fig. 276) brought together in the middle, one

from each side. Lacaze-Duthiers states that the processes are elongated

pleurae, but in the young it is far from clear that this is the case.

However that may be, they seem to convey air to the true breathing organs,

situate inside the cleft on the apical part of the abdomen itself; but

details as to the way in which transfer of air is effected along this

{564}very protracted passage are not forthcoming. The development in _Nepa_

has been studied to a certain extent. The apical stigmata are the only pair

of the abdominal stigmata that exist in the imago of _Nepa_, the other six

pairs being obliterated; the third, fourth, and fifth, according to

Schiödte, in a very peculiar manner: hence, as Martin says,[496] the

respiratory system is metapneustic. In an earlier stage of the life,

however, these six pairs of stigmata exist in functional activity placed in

a groove on the under surface of the body; so that the condition is that

termed peripneustic, and remains so till the final moult, when the long

siphon appears. In the early life there is a short prolongation from the

end of the body in connection with the pair of grooves alluded to, but it

is a single unpaired organ, and does little therefore to explain the

appearance of the siphon, which must, at present, be considered as being

suddenly developed at the last moult.

[Illustration: Fig. 277—Egg of _Nepa cinerea_. (After Korschelt.)]

The eggs of Nepidae are remarkable objects; that of the common

water-scorpion bears seven filaments at one end (Fig. 277); while that of

_Ranatra_ is more elongate, and bears only two, very elongate, threads.

These eggs are deposited in the stems of water-plants, being introduced

therein, so that the body of the egg is concealed while the threads

project: those of _Ranatra_ are placed in stems floating on the water, and

in consequence of the threads the stems look as if they were infested by

some fungus. The structure and formation of the eggs have been investigated

with considerable detail by Korschelt.[497] He looks on the filaments as

pneumatic, and considers that they supply a coating of air to the body of

the egg; they consist of a spongy mass encircled by two layers of

egg-shell, both of these latter being peculiar in structure; the spongy

mass is continuous with a layer of the same kind of substance placed on the

interior of the shell of the body {565}of the egg. It will be recollected

that we have described (p. 562) an egg, apparently of the same nature,

deposited by Capsids in the stems of land plants, so that it is very

doubtful whether the threads are really connected with the aquatic

development of the embryo in Nepidae. But the most interesting feature

connected with these eggs is, according to Korschelt, the mode of

development of the filaments, which is _sui generis_; the shell of the egg

is developed in the ordinary manner as an exudation or excretion from

epithelial cells; but the shell of the filament is formed as an

intracellular product; a mode of chitin-formation that appears to be

peculiar to this structure. Korschelt remarks that "it is in the highest

degree worthy of attention how by any process of development through a

large number of successive generations so complex a condition could be

established as the result of adaptation to external conditions; and this

becomes even more interesting when we remember that highly peculiar special

processes and departures from the usual modes of tissue-formation are

necessary to permit the development of this apparatus."[498]

FAM. 22. NAUCORIDAE.—_No ocelli, and no terminal process to the body; front

legs inserted on or near the front of the prosternum. Anterior femora

usually broad and flat._—The members of this family are truly aquatic, and

swim readily in the water. The family is small, including about nine genera

and thirty species, but, like many water-Insects, the genera are widely

distributed. We have two in Britain—one of them, _Naucoris_, common; the

other, _Aphelocheirus_, rare.

FAM. 23. BELOSTOMIDAE.—_No ocelli, and no long terminal tube to the body;

front legs inserted near the front of the prosternum. Posterior tibiae not

spiny; flattened and provided with swimming hairs._—Although these Insects

have been classified with Nepidae they have but little relation therewith;

on the other hand, the distinctions from Naucoridae are far less important.

The family includes some of the largest Insects. The South American

_Belostoma grande_ attains a length of four or four and a half inches.

Notwithstanding their considerable size Belostomidae exist in very large

numbers in some localities, and frequently destroy young fish by aid of the

powerful though short rostrum.

{566}[Illustration: Fig. 278—_Zaitha anura_, carrying eggs on its back.

West Indies.]

[Illustration: Fig. 279—Antenna of _Belostoma_ sp. A, One side of the under

surface of the head, with antenna, _b_, extended; B, with the antenna

retracted, _a_, Side of head; _c_, pocket for antenna; _d_, position of the

eyes. The corresponding joints of the antenna are numbered 1, 2, 3, 4 in

each figure.]

They appear to be unable to resist the attraction of artificial light, and

are consequently sometimes destroyed in large numbers. It has long been

known that species of the genera _Diplonychus_ and _Zaitha_ carry their

eggs on their backs. There is no special receptacle for the purpose, but

the eggs are kept in their peculiar position by means of a cement insoluble

in water. It has been stated by Dimmock that they are placed in position by

means of a long, flexible ovipositor. Schmidt, however, found that a

specimen of _Diplonychus_, bearing eggs and examined by him, was a male,

and he subsequently found that this was the case with other egg-bearing

individuals of other species, so that the mode in which the eggs are placed

in this position and the object of so curious a habit, remain uncertain.

The species of _Belostoma_ are highly remarkable on account of the curious

and complex structure of their antennae, in respect of which the nearest

analogy is to be found in the large Coleoptera of the genus _Hydrophilus_.

A very deep, ear-like pocket, exactly suited to the form of the antennae,

exists on the under side of the head; hence in repose no sign of the

peculiar shape of the antennae exists. When the antennae are placed in this

ear-like pocket only the one side of the basal joints is exposed, the long

processes being received into the deep pocket. In _Hydrophilus_ the antenna

is used as an accessory organ of respiration, and it will be interesting to

learn whether this is also the case in _Belostoma_. Belostomidae have

patches of air-carrying pubescence, analogous with those of _Hydrophilus_,

on the under sides of the body, elytra and wings, but we do not {567}know

how they are charged. Another extremely interesting analogy is found in the

manner in which the elytra are locked to the body; a projection from the

thoracic side-pieces, forming a long pouch, into which a fold on the inner

side of the elytra fits, the two being subsequently locked by the action of

some special projections. This arrangement is similar to that which exists

in the anomalous family of water-beetles Pelobiidae. In order to make this

mechanism more perfect the side-pieces in _Belostoma_ form free processes.

Martin has informed us that the young have the metasternal episternum

prolonged to form a lamella that he thinks may be for respiratory

purposes.[499] About twelve genera and upwards of fifty species of

Belostomidae are known. None exist in our isles, but several species extend

their range to Southern Europe. In the waters of the warm regions of the

continents of both the Old and New Worlds they are common Insects, but as

yet they have not been found in Australia.

FAM. 24. NOTONECTIDAE.—_Prosternum short, so that the legs are placed near

the back part of it as well as near the front; back of the head overlapped

by the front of the pronotum._—The water-boatmen are extremely common in

our ponds, where they may be seen rising to the surface and raising the

posterior extremity of the body for breathing. They swim on their backs

instead of in the usual position, and have an elaborate arrangement of long

hairs on the body to assist them to carry about an air-supply. They are

said to be lighter than the water, and to have some difficulty in keeping

away from the surface. _Notonecta glauca_ is the only British species, but

we have a second minute Insect, _Plea minutissima_, belonging to the

family. It lies in the mud at the bottom of shallow waters, and may

sometimes be fished up in great numbers. It is considered by some authors

to form a distinct family. The oviposition of _Notonecta_ has been observed

by Regimbart; the eggs are inserted into the stems of aquatic plants.

FAM. 25. CORIXIDAE.—_Prosternum short, as in Notonectidae; summit of the

head free from the thorax._—We have numerous species of the genus Corixa in

Britain; and others extremely similar in appearance occur in various parts

of the world. The head is remarkably free, and capable of great rotation.

On dissection it is found to be attached to the thorax only by a

{568}narrow area; in this respect it differs widely from _Notonecta_, which

possesses an extremely large occipital foramen, and the head of which

possesses but little freedom of movement. The extremely short proboscis is

more or less retractile, and therefore frequently appears absent. A second

British genus consists of a single species, _Sigara minutissima_. These

Insects, unlike _Notonecta_, are quite at home beneath the water, where

they scurry about with extreme rapidity, and occur sometimes in enormous

numbers. In Mexico the eggs of _Corixa americana_ and of _C. femorata_ are

used as food, and are said to be very nice. The Insects themselves are used

as food in both Mexico and Egypt. The species of this family can make a

noise beneath the water by rubbing the front feet against the

proboscis.[500] The males have a very complex asymmetry of the terminal

segments, and in some species possess on one side of the dorsal surface a

curious asymmetrical organ consisting of rows of very closely-packed,

intensely black, comb-like plates, called by Buchanan White a strigil. This

organ seems to be similar to the peculiar structures found on the terminal

segments of certain species of Scutellerides.

Sub-Order II. HOMOPTERA.[501]

FAM. 1. CICADIDAE.—_Head with three ocelli, placed triangularly on the

summit between the compound eyes; antennae consisting of a short basal

joint, surmounted by a hair-like process divided into about five segments.

Front femora more or less thick, armed with teeth. Peduncle (or basal

joints) of antennae without sensitive organs._—This important family

consists chiefly of large Insects, few being as small as one inch across

the expanded wings, while in some the expanse is as much as seven inches.

As a rule the four wings are transparent and shining, with the nervures

remarkably distinct and dark coloured; but there are numerous forms where

the whole creature, including the wings, is highly pigmented in a showy

manner; frequently in black and yellow. Cicadas are said to be without any

special protection, and to be destroyed in considerable numbers by birds

and other animals. The body is broad and robust, and is never shaped into

the extravagant forms we meet with in some of the other families of

Homoptera.

{569}[Illustration: Fig. 280—_Cicada septendecim._ North America. (After

Riley.) A, Larva; B, nymph; C, nymph skin after emergence of the imago, D;

E, section of twig with series of eggs; F, two eggs magnified.]