Little has been yet written as to the resemblances of Blattidae to other

species of their own family, or to other creatures, but it is probable that

such similarities will be found to prevail to a considerable extent. W. A.

Forbes has called attention[161] to the larva of a Blattid from Brazil as

being remarkable for its superficial resemblance to an Isopod crustacean.

Some of the wingless forms have a great resemblance to the small rolling-up

Myriapods of the group Glomerides; _Pseudoglomeris fornicata_, of which we

figure the female (Fig. 131), has received its name from this resemblance.

The females of the S. African genus _Derocalymma_ possess this Glomerid

appearance, and have a peculiar structure of the prothorax, admitting of a

more complete protection of the head. Brunner states that the wingless

kinds of _Derocalymma_ roll themselves up like wood-lice. In many of the

forms of this tribe—Perisphaeriides—the males are winged, though the

females are so like Myriapods. According to de Saussure[162] the gigantic

_Megaloblatta rufipes_ bears an extreme resemblance in appearance to the

large cockroaches of the genus _Blabera_.

[Illustration: FIG. 130.—_Gromphadorhina portentosa_, × ⅔. Tribe

Perisphaeriides. (After Brunner.)]

[Illustration: FIG. 131.—_Pseudoglomeris fornicata_, ♀. Burma. Tribe

Perisphaeriides. (After Brunner.)]

Some of the species of _Holocompsa_ remind us strongly of Hemiptera of the

family Capsidae; they have an arrangement of colours similar to what

prevails in that group, and their tegmina and wings which, as being those

of Blattids may be said to be abnormally formed, resemble in texture and

the distribution of the venation those of the Hemiptera. These Insects are

closely allied to _Diaphana_, of which genus we have figured a species

(Fig. 122).

{236}There is very little evidence on which to base an estimate of the

number of species of Blattidae existing in the world at present. Probably

the number extant in collections may amount to 1000 or thereabouts, and the

total existing in the world may be as many as 5000. The species of

Blattidae cannot tolerate cold, and are consequently only numerous in

tropical regions. Europe possesses about twenty species, and in Britain

there are only three that are truly native; these are all small Insects

belonging to the genus _Ectobia_, and living out of doors, amongst leaves,

under bushes, and in various other places. We have, however, several other

species that have been introduced by the agency of man, and these all live

under cover, where there is artificial warmth and they are protected from

the inclemencies of the winter season. The commonest of these forms is

_Stilopyga orientalis_, the "black beetle" of our kitchens and bakehouses.

This Insect is said to have been brought to Europe from "Asia" about 200

years ago, but the evidence as to its introduction, and as to the country

of which it is really a native, is very slight. It is indeed said[163] that

_S. orientalis_ has been found in peat in Schleswig-Holstein. _Periplaneta

americana_ is a larger Insect, and is common in some places; it is

apparently the species that is most usually found on board ships, where it

sometimes multiplies enormously, and entirely devours stores of farinaceous

food to which it obtains access: it is known that sometimes a box or barrel

supposed to contain biscuits, on being opened is found to have its edible

contents entirely replaced by a mass of living cockroaches. Fortunately

_Periplaneta americana_ has not spread widely in this country, though it is

found in great numbers in limited localities; one of the best known of

which is the Zoological Gardens in the Regent's Park at London.

_Periplaneta australasiae_ is very similar to _P. americana_, but has a

yellow mark on the shoulder of each tegmen. This has obtained a footing in

some of the glass-houses in the Botanic Gardens at Cambridge and Kew; and

it is said to be fairly well established in Belfast. Another of our

introduced domestic cockroaches is _Phyllodromia germanica_, a much smaller

Insect than the others we have mentioned. It has only established itself at

a few places in this country, but it is extremely abundant in some parts of

Northern and Eastern Europe. It has been increasing in numbers in Vienna,

where, according to Brunner, it is {237}displacing _Stilopyga orientalis_.

In addition to these, _Rhyparobia maderae_ and species of the genus

_Blabera_ have been met with in our docks, and are possibly always to be

found there. They are Insects of much larger size than those we have

mentioned. We figure the alar organs of one of these species of _Blabera_

of the natural size: the species in this genus are extremely similar to one

another. Blaberae are known in the West Indies as drummers, it being

supposed that they make a noise at night,[164] but details in confirmation

of this statement are wanting.

[Illustration: FIG. 132.—Alar organs of _Blabera_ sp. A, tegmen; B, wing.]

It is a remarkable fact that no satisfactory reasons can be assigned for

the prevalence of one rather than another of these domestic cockroaches in

particular localities. It does not seem to depend at all on size, or on the

period of development, for the three species _Stilopyga orientalis_,

_Periplaneta americana_, and _Phyllodromia germanica_, which are the most

abundant, differ much in these respects, and replace one another in

particular localities, so that it does not appear that any one is gaining a

permanent or widespread superiority as compared with another. There are,

however, no sufficient records on these points, and further investigation

may reveal facts of which we are at present ignorant, and which will throw

some light on this subject. We may remark that Mr. Brindley has found it

more difficult to obtain hatching of the young from the egg-capsules of

_Periplaneta americana_ and _Phyllodromia germanica_ at Cambridge, than

from those of _Stilopyga orientalis_.

Although much work has been done on the embryology of Blattidae, the

subject is still very incomplete. The recent memoirs of Cholodkovsky[165]

on _Phyllodromia germanica_ contain so much of general interest as to the

development of the external parts of the body that we may briefly allude to

them. The earliest appearance of segmentation appears to be due to the

centralisation of numerous {238}cells round certain points in the ventral

plate. The segmentation of the anterior parts is first distinct, and the

appearance of the appendages of the body takes place in regular order from

before backwards, the antennae appearing first; the mandibles, however,

become distinct only subsequent to the maxillae and thoracic appendages.

There are in the course of the development appendages to each segment of

the body (he counts eleven abdominal segments); the cerci develop in a

similar manner to the antennae; the first pair of abdominal appendages—at

first similar to the others—afterwards assume a peculiar stalked form. The

abdominal appendages subsequently disappear, with the exception of the

ninth pair, which form the ventral styles, and the eleventh pair, which

become the cerci. The last ventral segment is said to be formed by the

union of the tenth and eleventh embryonic ventral segments.

[Illustration: FIG. 133.—A, Tegmen(?) of _Palaeoblattina douvillei_; B, of

_Etoblattina manebachensis_. (After Brauer and Scudder.)]

As regards their Palaeontological forms Blattidae are amongst the most

interesting of Insects, for it is certain that in the Carboniferous epoch

they existed in considerable number and variety. A still earlier fossil has

been found in the Silurian sandstone of Calvados; it consists of a fragment

(Fig. 133, A), looking somewhat like an imperfect tegmen of a Blattid; it

was described by Brongniart under the name of _Palaeoblattina douvillei_,

and referred by him, with some doubt, to this family. Brauer has, however,

expressed the opinion[166] that the fragment more probably belonged to an

Insect like the mole-cricket, and in view of this discrepancy of

authorities we may be pardoned for expressing our own opinion to the effect

that the relic has no connexion with the Insecta. The figure given by

Scudder[167] has not, however, so uninsect-like an appearance as that we

have copied from Brauer. Whatever may prove to be the case with regard to

_Palaeoblattina_, it is certain, as we {239}have already said, that in the

Palaeozoic epoch Insects similar to our existing cockroaches were abundant,

their remains being found in plenty in the coal-measures both of Europe and

North America. Fig. 133, B, shows a fossil tegmen of _Etoblattina

manebachensis_ from the upper Carboniferous beds of Ilmenau in Germany. It

will be noticed that the disposition of the nervures is very much like that

which may be seen in some of our existing Blattidae (cf. the tegmen of

_Blabera_, Fig. 132, A), the vena dividens (_a_) being similarly placed, as

is also the mediastinal vein on the front part of the organ. The numerous

carboniferous Blattidae have been separated as a distinct Order of Insects

by Scudder under the name Palaeoblattariae, but apparently rather on

theoretical grounds than because of any ascertained important structural

distinctions. He also divided the Palaeoblattariae into two groups,

Mylacridae and Blattinariae, the former of which was supposed to be

peculiar to America. Brongniart has, however, recently discovered that in

the Carboniferous deposits of Commentry in France Mylacridae are as common

as in America. This latter authority also states that some of the females

of these fossil Blattidae are distinguished by the presence of an elongate

exserted organ at the end of the body. He considers this to have been an

ovipositor by which the eggs were deposited in trees or other receptacles,

after a manner that is common in certain Orthoptera at the present day. If

this view be correct these Carboniferous Insects must have been very

different from the Blattidae of our own epoch, one of whose marked

characteristics is the deposition of the eggs in a capsule formed in the

body of the parent.

In the strata of the secondary epoch remains of Blattidae have also been

discovered in both Europe and America, in Oolitic, Liassic, and Triassic

deposits. From the Tertiary strata, on the other hand, comparatively few

species have been brought to light. A few have been discovered preserved in

amber.

[Illustration: FIG. 134.—Front leg of _Periplaneta australasiae_.]

The classification of the Blattidae is attended with considerable

difficulty on account of the numerous wingless forms, and of the

{240}extreme difference in the organisation of the two sexes of many

species. It has, however, been brought to a fairly satisfactory state by

the reiterated labours of Brunner von Wattenwyl, and we reproduce his

recently perfected exposition of their characters. His first division is

made by means of a structure which is very easily observed, viz. whether

the femora are armed with spines, as in Fig. 134, or not. The terms used in

connexion with the wings and other parts of the body we have already

explained.

Brunner's system is adopted by de Saussure,[168] who, however, proposes to

replace the names Ectobiides and Oxyhaloides by Anaplectinae and

Plectopterinae. He also proposes to apply the generic name _Blatta_ to the

Insect that is now so frequently called _Phyllodromia germanica_ in

zoological works. If that view be adopted, Brunner's group Phyllodromiides

will be called Blattides.

Table of the tribes of Blattidae, after Brunner:—

1. Femora spiny beneath.[169]

2. The last ventral plate of the female large, without valves.

3. Supra-anal lamina of both male and female transverse, narrow.

Wings, when present, furnished with a triangular apical field.

Posterior femora unarmed beneath, or armed with two spines on the

anterior margin. Egg-capsules furnished with a longitudinal suture.

Tribe 1. ECTOBIIDES. [Anaplectinae Saussure.]

3′. Supra-anal lamina of each sex more or less produced, triangular,

or emarginate. Wings, when present, without apical field. Posterior

femora with both edges spiny.

4. Supra-anal lamina of each sex triangular, not notched. Cerci

projecting much beyond this lamina.

5. Pronotum and elytra smooth (_i.e._ without peculiarity of

surface other than punctuation). The radial nervure of the wing

giving off several parallel branches, pectinate on the anterior

margin (except in the genus _Abrodiaeta_). Tarsal joints without

pads. Tribe 2. PHYLLODROMIIDES. [Blattinae Saussure.]

5′. Pronotum and elytra holosericeous. Radial nervure of the

wings giving off irregular branches on the anterior margin (ulnar

vein many-branched). Tarsal joints furnished with pads. Tribe 3.

NYCTIBORIDES.

4′. Supra-anal lamina of males more or less four-sided, with obtuse

angles, of females broad, rounded, or lobed. Cerci not projecting

beyond the lamina. (Tarsal joints with distinct pads.) Ulnar

nervure of the wings giving off parallel branches towards the vena

dividens. Tribe 4. EPILAMPRIDES.

{241}2′. The last ventral plate of the female furnished with valves.

Tribe 5. PERIPLANETIDES.[170] (Fig. 119, _Periplaneta australasiae_.)

1′. Femora unarmed beneath. (In the tribe Panesthiides the anterior

femora are frequently armed with two spines.)

2. Supra-anal lamina of each sex more or less produced, posterior

margin notched.

3. A distinct pad between the claws. Tribe 6. PANCHLORIDES.

3′. No pad between the claws, or only an excessively small one.

4. Wings with a folded fan-like anal field. Pronotum smooth. Tribe

7. BLABERIDES. (Fig. 132, _Blabera_ sp. wings.)

4′. Anal field of the wing with a single fold. Pronotum more or

less pilose. Tribe 8. CORYDIIDES. (Fig. 128, _Corydia petiveriana_.

Fig. 118, _Heterogamia aegyptiaca_.)

2′. Supra-anal lamina of each sex, short, transverse, posterior margin

straight or rounded.

3. Subgenital lamina of the male somewhat produced, furnished with a

single style. Tarsal claws with a distinct pad (except in the genus

_Paranauphoeta_).

4. Anterior portion of the wings pointed, either the apical field

of the wing very much produced, or the wings twice as long as the

tegmina, folded in repose. Tribe 9. OXYHALOIDES. [Plectopterinae

Saussure.] (Fig. 129, _Hypnorna amoena_.)

4′. Anterior portion of wing, when present, rounded, with no apical

field. Tribe 10. PERISPHAERIIDES. (Fig. 130, _Gromphadorhina

portentosa_; Fig. 131, _Pseudoglomeris fornicata_.)

3′. Subgenital lamina of males extremely small, without styles. No

pad between claws. Tribe 11. PANESTHIIDES.

To the above tribes another one—GEOSCAPHEUSIDES—has been recently added by

Tepper,[171] for an extraordinary Australian Insect of fossorial habits,

with front legs formed somewhat like those of _Gryllotalpa_.

{242}CHAPTER X

ORTHOPTERA _CONTINUED_—MANTIDAE—SOOTHSAYERS

FAM. IV. MANTIDAE—SOOTHSAYERS OR PRAYING INSECTS.

_Orthoptera with exserted but deflexed head and elongate prothorax, the

first pair of legs largely developed, raptorial, the coxae elongate,

free, femora and tibiae armed with spines: second and third pair of legs

simple and similar; the tarsi five-jointed, without a pad (arolium)

between the claws; a pair of jointed cerci near the extremity of the

body._

The Mantidae are an extensive family of Orthoptera, showing extreme variety

in the shapes and outlines of the body, and characterised by the very

remarkable front legs; the function of these legs being to seize and hold

their prey, which consists of living Insects, Mantidae being carnivorous

and highly voracious.

The labium is deeply divided, each half exhibiting a very near approach to

the structure of a maxilla; there is a large membranous lingua reposing on

the inner face of the lower lip. The head is quite free from the thorax,

its front part being deflexed, and even somewhat inflexed, so that the

mouth is directed downwards and somewhat backwards: it is very mobile,

being connected to the thorax by a comparatively slender neck, which is,

however, concealed by the pronotum. There are two large, prominent eyes,

the antennae are frequently very slender, but they sometimes differ

according to sex, and in some genera are pectinate in the male; just above

and between their insertion are three ocelli placed in a triangle, two

above, one below; between the antennae and the clypeus there is an interval

called the scutellar space. In some forms of Mantidae the head assumes most

extraordinary shapes; the eyes may become {243}elongate and horn-like;

there may be a projection between them bearing the ocelli, and attaining

occasionally a great length; the scutellar space also may have a remarkable

development, the whole thus forming a peculiar ornamental structure, as in

Fig. 136.

[Illustration: FIG. 135.—_Deroplatys sarawaca_, female. Borneo. (After

Westwood.)]

The prothorax is elongate, but there are a few genera, _e.g._

_Eremiaphila_, in which it is exceptionally short, and there are several

others in which the elongate form is more or less masked by foliaceous

expansions of the sides. The pronotum shows near the front a transverse

depression or seam, which marks the position of an internal chitinous

ridge. The anterior legs are {244}inserted near the front of the

prosternum, which extends less far forwards than the pronotum does; the

posterior part of the prosternum is very elongate, and is completely

separated from the anterior part by the base of the coxae and the membranes

attached to them; the pronotum and sternum are closely connected at the

sides till near the posterior part where they diverge, the space so formed

being occupied by a membrane in which the prothoracic stigma is situated.

The mesothorax is as long as broad, and the front wings are attached to the

whole length of the sides; the mesosternum is a triangular piece pointed

behind, and bearing very large side-pieces, to the hinder portion of which

the middle coxae are attached; these latter are large and quite free, and

repose on the metasternum which they cover; the mesothoracic stigma may be

detected as a slit situated on a slight prominence just behind and a little

below the membranous hind-margin of the tegmen. The metathorax differs

comparatively little in size and structure from the mesothorax; the

membranous hind wings are attached to the sides of the notum along nearly

the whole length of the latter. The abdomen is moderately long; in each sex

ten dorsal plates may be detected, and there is a pair of ringed cerci

projecting from beneath the sides of the tenth plate. The number of ventral

plates is more difficult to verify, the first one being much reduced; eight

other plates can be demonstrated in the male and six in the female.

[Illustration: FIG. 136.—Head of _Harpax variegatus_, seen from the front.]

The anterior legs are formed in a remarkable manner in the Mantidae, and

are, in fact, the most characteristic feature of the family. Attached near

the front of the thorax there is a very long coxa, to the apex of which is

articulated the triangular trochanter; this bears the elongate femur, which

is furnished on its lower face with sharp spines and teeth; the tibia which

follows is much shorter and smaller than the femur; its lower face bears

also an armature of teeth, and it is so articulated with {245}the femur

that it can be completely closed thereon, its teeth fitting in among those

of the femur (Fig. 137, B); the latter has one or more longer spines

overlapping the apical part of the tibia when contracted. The tarsus is

slender, five-jointed, without pad. The other two pairs of legs are simple;

the hinder usually a little the longer, and in some species that possess

powers of leaping (_Ameles_), with the femora a little thicker at the base.

[Illustration: FIG. 137.—Front leg of _Empusa pauperata_, female: A, with

tibia extended and tarsus wanting; B, more magnified (the basal parts

removed), showing the mode of closure.]

The alar organs of the Mantidae are as regards the nervures and areas

fairly similar to those of the Blattidae. The tegmina are usually narrow,

and exhibit three well-marked areas; the one in front or external

(according as the wing is expanded or closed) is the mediastinal area; it

is usually more elongate and occupies a larger portion of the surface of

the tegmen than in Blattidae. The middle area, forming the larger part of

the wing, is occupied by the branches of the radial and ulnar nervures. The

third area, the anal, possesses a sort of appendage in the form of a small

space of a more delicately membranous nature at the inner part of the base.

The tegmina are often more or less leaf-like in texture and consistence;

this character is as a rule not very marked, but there are a few species

with the tegmina very like foliage, this being more marked in the female;

in some, if not in all, of these cases the mediastinal area is considerably

increased. One tegmen overlaps the other, as in Blattidae, but to a less

extent, and the correlative asymmetry is but slight: there is frequently a

pallid spot close to the main vein on the principal area, nearer to the

base than to the extremity. The hind wings are more ample than the front,

and of much more delicate consistence; they possess numerous veins

converging to the base; the anterior part of the wing is firmer in

consistence, and its veins are more numerously furcate; there are many more

or less distinct minute cross-veinlets, and an elegant tinting is not

infrequent. They close in a fan-like manner, transverse folding being

unknown in the family.

{246}But little has been written on the internal anatomy of the Mantidae.

Dufour has described only very partially that of _M. religiosa_. The

salivary glands are largely developed, salivary receptacles exist; the

alimentary canal possesses eight elongate coecal diverticula placed on the

chylific ventricle; there are about one hundred Malphigian tubules. In each

ovary there are about 40 egg-tubes, and they are joined at their bases in

clusters of about half a dozen; each cluster has a common sinus; these

sinuses are placed at intervals along a tube, which is one of two branches

whose union forms the oviduct; there are a large number of "serific glands"

of two kinds in the female. The testes are unusually complex in their

structure.

According to Schindler[172] the Malphigian tubes in _Mantis_ are not

inserted, as usual, at the base of the intestine, but on the intestine

itself at about one-third of its length from the base. There is some doubt

about this observation. Schindler considers the fact, if it be such,

unique.

The eggs of the Mantidae are deposited in a singular manner: the female,

placing the extremity of the body against a twig or stone, emits some

foam-like matter in which the eggs are contained. This substance dries and

forms the ootheca; whilst attaining a sufficient consistence it is

maintained in position by the extremity of the body and the tips of the

elytra, and it is shaped and fashioned by these parts. The eggs are not, as

might be supposed, distributed at random through the case, but are lodged

in symmetrically-arranged chambers, though how these chambers come into

existence by the aid of so simple a mode of construction does not appear.

The capsule is hard; it quite conceals the eggs, which might very naturally

be supposed to be efficiently protected by their covering: this does not,

however, appear to be the case, as it is recorded that they are subject to

the attacks of Hymenopterous parasites. The time that elapses after the

eggs are laid and before they hatch varies greatly according to

circumstances. In France, _Mantis religiosa_ deposits its eggs in

September, but they do not hatch until the following June; while in E.

India the young of another species of _Mantis_ emerge from the eggs about

twenty days after these have been deposited. Trimen has recorded some

particulars as to the formation of its egg-case by a _Mantis_ in S. Africa.

This {247}specimen constructed four nests of eggs at intervals of about a

fortnight, and Trimen states that the four were "as nearly as possible of

the same size and of precisely similar shape." He also describes its mode

of feeding, and says that it was fond of house-flies, and would eat

"blue-bottles," i.e. _Musca vomitoria_, but if while eating one of the

latter a house-fly were introduced, the "blue-bottle" was generally

dropped, even though it might be in process of being devoured. The young

have to escape from the chambers in which they are confined in these

egg-cases; they do so in a most curious manner; not by the use of the feet,

but by means of spines directed backwards on the cerci and legs, so that

when the body is agitated advance is made in only one direction. The eggs

last deposited are said to be the first to hatch. On reaching the exterior

the young Mantids do not fall to the ground, but remain suspended, after

the manner of spiders, to the ootheca by means of two threads attached to

the extremities of the cerci; in this strange position they remain for some

days until the first change of skin is effected, after which they commence

the activity of their predatory life.

[Illustration: FIG. 138.—Egg-case of _Mantis_ with young escaping: A, the

case with young in their position of suspension; B, cerci magnified,

showing the suspensory threads. (After Brongniart.)]

Dr. Pagenstecher has given an account[173] of the development of _Mantis

religiosa_, from which it would appear that the statements of Fischer and

others as to the number of moults are erroneous, owing to the earliest

stages not having been observed. When the young _Mantis_ emerges from the

egg it bears little resemblance to the future Insect, but looks more like a

tiny pupa; the front legs, that will afterwards become so remarkable, are

short and not different from the others, and the head is in a curious

mummy-like state, with the mouth-parts undeveloped and is inflexed on the

breast: there are, he says, nine abdominal segments. The first ecdysis soon

takes place and the creature is thereafter recognisable as a young

_Mantis_. Pagenstecher's specimens at first would only eat Aphididae, but

at a later stage of the {248}development they devoured other Insects

greedily: the number of ecdyses is seven or eight. The ocelli appear for

the first time when the wing rudiments do so; the number of joints in the

antennae increases at each moult. Dr. Pagenstecher considers that this

Insect undergoes its chief metamorphosis immediately after leaving the egg,

the earlier condition existing apparently to fit the Insect for escaping

from the egg-case. In the immature stage of the Mantidae the alar organs

appear (Fig. 139) as adjuncts of the sides of the meso- and meta-notum,

projecting backwards and very deeply furrowed and ribbed in a wing-like

manner. According to Pagenstecher, this wing-like appearance only commences

in the fifth stadium, but he has not given particulars of the conditions of

these parts in the preceding instars. According to de Saussure[174] the

wings of the females of some species remain permanently in this undeveloped

or nymphal state.

[Illustration: FIG. 139.—Tegmina (_t_) and wings (_w_) of immature

_Mantis_.]

[Illustration: FIG. 140.—_Iris oratoria_, female. South Europe. Natural

size.]

The Mantidae, as a rule, have a quiet unobtrusive mien, and were it not for

their formidable front legs would look the picture of innocence; they,

however, hold these legs in such manner as to greatly detract from the

forbidding appearance thereof, stretching them out only partially so as to

give rise to an appearance of supplication or prayer;[175] this effect is

increased by their holding themselves in a semi-erect position, standing on

the hind and middle legs with the upper parts of the body directed somewhat

forwards, hence they are called by various names indicating prayer or

supplication, and it is said that in some countries they are considered

sacred. Some of the older {249}writers went so far as to say that a

_Mantis_ would indicate the road a child should take by stretching out one

of its arms in the right direction. The traveller Burchell, speaking of a

species since described by Westwood under the name of _Tarachodes

lucubrans_, says: "I have become acquainted with a new species of _Mantis_,

whose presence became afterwards sufficiently familiar to me by its never

failing, on calm warm evenings, to pay me a visit as I was writing my

journal, and sometimes to interrupt my lucubrations by putting out the

lamp. All the _Mantis_ tribe are very remarkable Insects; and this one,

whose dusky sober colouring well suits the obscurity of night, is certainly

so, by the very late hours it keeps. It often settled on my book, or on the

press where I was writing, and remained still, as if considering some

affair of importance, with an appearance of intelligence which had a

wonderful effect in withholding my hand from doing it harm. Although

hundreds have flown within my power, I never took more than five. I have

given to this curious little creature the name of _Mantis lucubrans_; and

having no doubt that he will introduce himself to every traveller who comes

into this country [Southern Africa] in the months of November and December,

I beg to recommend him as a harmless little companion, and entreat that

kindness and mercy may be shown to him." This appearance of innocence and

quietness must have struck all who have seen these Insects alive;

nevertheless, it is of the most deceptive character, for the creature's

activity consists of a series of wholesale massacres carried on day after

day, the number of victims it sacrifices being enormous. The _Mantis_ does

not even spare its own kind; it is well known that the female not

unfrequently devours its own mate. A very different picture to that of

Burchell has been drawn by Potts, who observed the habits of a species in

New Zealand.[176] He informs us that when about making an attack it

approaches its intended prey with slow, deliberate movements, its anterior

limbs folded in an innocent fashion, now and then raising itself or lifting

the prothorax in a stealthy quiet manner, perhaps to judge accurately of

its distance; when near enough, with one swift dart the victim is secured.

The prey is held {250}firmly in the formidable trap formed by the anterior

leg, and is thus brought near the mouth. The _Mantis_ usually commences its

feast by taking off some portions of the head of its wretched victim, and

displays an absolute indifference to its struggling or kicking; the

mandibles having seized a portion of the food, the legs holding it move

away, thus leaving a fragment in the mouth. Portions only of a captured

Insect are consumed, much being cast away; and Mr. Potts states that he has

seen one of these voracious creatures kill and devour parts of fourteen

small flies within a very brief space of time. This voracity and waste of

animal food is very remarkable when we recollect that many Insects have

such perfect powers of assimilation that during their whole period of

growth they only consume a mass of food—and that vegetable—but little

larger in size than the bulk they themselves attain. This fact is well

known in the case of _Bruchus_, _Caryoborus_, and other seed-feeding

Insects. Burmeister has stated good grounds for believing that some of the

larger Mantidae do not confine themselves to Insect diet, but attack and

devour small Vertebrates.[177] He has given a circumstantial account of a

case at Buenos Ayres, where a small bird was secured by the wingless female

of a large _Mantis_, which had commenced devouring its head when the

observer took possession of the creature and its booty. Dubois states[178]

that when a decapitated, but living, _Mantis_ was suspending itself to a

roll of drapery by its four posterior legs, a person could detach with the

fingers the left anterior leg (of the four) and the right posterior, or

conversely the left posterior and right anterior, without the interference

producing any action on the part of the creature; but if one of the other

legs was also interfered with, which would necessarily have changed the

position of the body, then immediately one of the two unoccupied legs was

placed by the creature in a proper position to assure its stability. This

reflex action altogether resembled in appearance a conscious action, and

was as effectually performed.

The combination in Mantidae of voracious and destructive instincts with

helpless and inert attitudes gives rise to the idea that these latter are

adopted for the purpose of deceiving the living prey and of thus more

easily obtaining the means of subsistence. {251}It appears, however, more

probable that the helpless attitudes have no such origin, but are due to

the structure and form of the creature. The front legs being wonderfully

well formed for raptorial purposes, have no capacity for locomotion or for

supporting the Insect in the usual manner, so that the body has to be borne

by the hinder two pairs of legs; at the same time the raptorial pair of

limbs—which, it will be recollected, are of great size and attached to the

anterior part of an unusually long prothorax—have to be held in such a

position as will not derange the equilibrium maintained by the posterior

part of the body; moreover, these large raptorial legs are entirely

exserted, and have no trace of any articulatory cavity that might act as a

mechanical aid to their support. Thus they could not be held extended

without great muscular exhaustion; hence we can well believe that the

sedentary and helpless attitudes of the creature are not the results of any

guile.

A _Mantis_ has been recorded as bearing a close resemblance to a Phasmid of

the genus _Bacillus_ and having only small front legs; it was suggested by

Bates[179] that the Mantis would probably be found to feed on the

_Bacillus_. Though the case is of considerable interest, no further

information about it has been obtained.

[Illustration: FIG. 141.—_Mantoida luteola_ Westw., male. Santarem.]

The simplest forms of the family are found in the groups Amorphoscelides

and Orthoderides. From our figure of one of these (Fig. 141, _Mantoida

luteola_ ♂), it will be seen that the peculiarities of the family can

scarcely be detected, the raptorial legs being very little developed and

the prothorax short. The sexes, too, differ but little in these simple

forms. Most of them are very rare in collections, but Wood-Mason

states[180] that _Amorphoscelis annulicornis_ is frequently found about

Calcutta on the trunks of trees, to the bark of which it is so similar that

it is only discovered with difficulty. In its rapid movements it resembles

the cockroaches or _Machilis_, more than it does the more differentiated

forms of its own group.

{252}In the genus _Pyrgomantis_ (Fig. 142, _P. singularis_, female) the

male has the tegmina and wings of normal size, while in the female they are

rudimentary.

[Illustration: FIG. 142.—_Pyrgomantis singularis_, female. S. Africa.

(After Westwood.)]

[Illustration: FIG. 143.—Outline of _Chaeradodis cancellata_ ♀, nymph.

(After Wood-Mason.)]

The variety of shape and external appearance in this family is very great;

de Saussure considers it to be a mimetic group. In certain species some

parts of the body—more especially the tegmina—have very much the appearance

of foliage, and usually in such cases this appearance is confined to the

female, the males in this family having, as we have said, the organs of

flight more transparent and colourless; in the former sex the alar organs,

when present, are frequently but little adapted for flying. In some species

the prothorax is expanded at the sides (Fig. 135, _Deroplatys sarawaca_;

and Fig. 143, _Choeradodis cancellata_), and in such cases the outline of

the natural thorax—if we may use such an expression—may be detected

occupying the middle of the unusual expansion. The European _Mantis

religiosa_ varies much in colour; in some examples the tegmina are

leaf-green, while in others they are brown or gray. There is some evidence

extant making it probable that in some species the colour of an individual

changes at different times—Colonel Bowker saying of {253}_Harpax ocellata_

that it "beats the Chameleon hollow in changing colour."

Some of the species of the old genus _Eremiaphila_ (Fig. 144) are of very

unusual form. De Saussure considers that some species of this genus are

more highly modified than any other animals for maintaining their existence

in desert regions. They are said to be found in places where no vegetation

exists, and to assimilate in appearance with the sandy soil, the species

varying in colour, so that the individuals agree in tint with the soil on

which they dwell. These Insects are referred to the group Orthoderides, and

have a short prothorax, the alar organs being unsuited for flight. What

they live on is not actually known; although other Insects are the natural

food of Mantids, it is said that these desert-frequenting species occur in

spots where no other Insect life is known to exist. Lefebvre[181] met with

these Eremiaphilas in the desert between the Nile and the Northern Oasis,

El Bahryeh, but was quite unable to discover their mode of subsistence.

These Insects are very rare in collections, and the information we possess

about them is very meagre.

[Illustration: FIG. 144.—_Eremiaphila turcica._ (After Westwood.)]

Mr. Graham Kerr found on the Pilcomayo river a species of Mantidae living

on branches of trees amongst lichens, which it so exactly resembled that it

was only detected by the movement of a limb; it was accompanied by a

Phaneropterid grasshopper, which bore a similar resemblance to the lichens.

One of the rarest and most remarkable forms of Mantidae is the genus

_Toxodera_, in which the eyes project outwards as pointed cones (Fig. 145).

These Insects offer an interesting problem for study, since we are entirely

ignorant about them. Brunner places the Toxoderae in his tribe Harpagides,

but with the remark that "these Insects of antediluvian shapes differ

essentially from all other Mantidae."

Wood-Mason informs us[182] that the young of _Hymenopus bicornis_

{254}beautifully simulate blossoms of different colours. And it has been

stated by Dr. Wallace, on the authority of a communication made to him by

Sir Charles Dilke, that a small _Mantis_ found in Java exactly resembles a

pink Orchis-flower, and this species "was not only said to attract Insects,

but even the kind of Insects (butterflies) which it allures and devours was

mentioned." We do not know of what species or genus this Insect may be, but

_Hymenopus bicornis_ is a peculiar form of the tribe Harpagides, and has,

together with its younger state, been figured long ago by Caspar Stoll in

his quaint and interesting old book.[183] Though it has very peculiar

foliaceous expansions on the two hinder pairs of legs, these dilatations

are very different from those seen in the curious _Gongylus gongylodes_,

the female of which we figure (Fig. 146). This latter, according to the

information we shall quote, is also a "floral simulator." Specimens of _G.

gongylodes_ were shown to the members of the Asiatic Society of Bengal in

1877 by Dr. J. Anderson,[184] who at the same gave some information about

them which we shall reproduce in full, because, incomplete as it is, it is

apparently almost the sole piece of definite information we possess as to

this curious Insect, or any of its congeners:—

[Illustration: FIG. 145.—_Toxodera denticulata_, male. Java. (After

Serville.)]

"These Insects all came from the same locality, having been {255}forwarded

to Mr. Buckland by Mr. Larymore of the Central Jail at Midnapur. Mr.

Larymore had procured them from the neighbouring country district, where

Santál women and children had hunted them out and brought them in, hanging

on branches or twigs of a bush, somewhat like a wild plum-tree. They are

also said to be found upon rose-bushes, and in connexion with this it was

observed that, in Midnapur, they were known as rose-leaf Insects, from the

circumstance that when the Insect is more developed and furnished with

wings, the foliaceous appendages are said greatly to increase in size, and

exactly to resemble rose-leaves. Dr. Anderson, however, was disposed to

think that more than one species might probably occur in the Midnapur

district, and that these Insects with the larger foliaceous expansions

might be distinct from the species now before the Society.

[Illustration: FIG. 146.—_Gongylus gongylodes_, female. East India.]

{256}"Mr. Buckland had made over these Insects to Dr. Anderson, and since

that time they have been regularly fed upon house-flies and grasshoppers;

the latter, however, appear to be rather too strong for them, and they

therefore prefer the flies. They have been tried with small fragments of

plaintain and custard-apple, which they not only eat, but the juice of

which they seem to suck with considerable avidity, Dr. Anderson, however,

thought that it was the moisture of these fruits that was the chief

attraction to these Insects, for the entire character of their organisation

indicated a raptorial habit.

"Dr. Anderson went on to say that he had succeeded in identifying the three

larger Insects by means of a single dried specimen in the Indian Museum,

which, however, was fully mature and provided with wings. These remarkable

Insects proved to be the pupae of a peculiar species of _Mantis_ which was

known to Aldrovandus, who figured it more than a century and a half before

the first appearance of the Systema Naturae of Linnaeus, to whom it was

known as _Gryllus gongylodes_, and also as _Mantis gongylodes_; and since

the time of Aldrovandus it had been figured in a variety of works on

Natural History, but apparently in every instance from mature, and

seemingly dried specimens, so that the colours of the Insect during life

had never been correctly described.

"So much by way of introduction to these remarkable pupal Mantises, the

recognised scientific name of which is _Gongylus gongylodes_ L.

"The reason which induced Dr. Anderson to bring them to the notice of the

Society had now to be pointed out. On looking at the Insects from above,

they did not exhibit any very striking features beyond the leaf-like

expansion of the prothorax and the foliaceous appendages to the limbs, both

of which, like the upper surface of the Insect, are coloured green, but on

turning to the under surface the aspect is entirely different. The

leaf-like expansion of the prothorax; instead of being green, is a clear,

pale lavender-violet, with a faint pink bloom along the edges of the leaf,

so that this portion of the Insect has the exact appearance of the corolla

of a plant, a floral simulation which is perfected by the presence of a

dark, blackish brown spot in the centre, over the prothorax, and which

mimics the opening to the tube of a corolla. A favourite position of this

Insect is to hang head {257}downwards among a mass of green foliage, and,

when it does so, it generally remains almost motionless, but, at intervals,

evinces a swaying movement as of a flower touched by a gentle breeze; and

while in this attitude, with its fore-limbs banded violet and black, and

drawn up in front of the centre of the corolla, the simulation of a

papilionaceous flower is complete. The object of the bright colouring of

the under surface of the prothoracic expansion is evident, its purpose

being to act as a decoy to Insects, which, mistaking it for a corolla, fly

directly into the expectant, serrated, sabre-like, raptorial arms of the

simulator. It is no new fact that many Insects resemble the leaves of

plants and trees, and that they manifest forms and colours which serve to

protect them in the struggle for existence, but so far as Dr. Anderson had

ascertained, this was the first recorded instance of an Insect simulating

the corolla of a flower for the evident purpose of attracting Insects

towards it for its sustenance. It is even more remarkable than this, for it

is a localised adaptation for such a purpose, a portion of the Insect being

so modified in form and colour that the appearance of the corolla of a

plant is produced, in conjunction with the remainder of the long attenuated

prothorax, which at a distance resembles the flower stem; the anterior

limbs when in repose even adding to and heightening the deception."

That we should have no more precise information as to a large Insect of

such remarkable habits and appearance, and one that has been known to

naturalists for upwards of three centuries, is a matter for regret. Careful

observation as to the habits, food, and variation of these floral

simulators, and as to whether they seek for spots specially suitable to

their coloration, would be of great interest. A European congener of this

Insect, _Empusa pauperata_, has small foliaceous expansions on the legs,

but its habits have not been noticed in detail.

The very curious Insect represented in Fig. 147, _Stenophylla cornigera_,

is a member of the tribe Vatides; the form of the cerci at the end of the

body is very peculiar. This extremely rare, if not absolutely unique,

Insect is a native of the interior of Brazil.

Dufour has recorded that _Mantis religiosa_ possesses the power of

producing a mournful sound by rubbing the extremity of the body against the

wings; it is stated that a hissing sound is {258}produced by other species,

and Wood-Mason has suggested[185] that a special structure exists on the

tegmina for the purpose.

There are probably about 600 species of Mantidae known; they are

distributed over all the warmer parts of the earth, but there are none in

the cooler regions. Europe possesses some twelve or fourteen species, most

of them confined to the Mediterranean sub-region; a single species, _Mantis

religiosa_, is frequently found in Central France, and has been recorded as

occurring as far north as Havre. Although no species is a native of

Britain, it is not difficult to keep them alive here. Denny records[186]

that an egg-case of a _Mantis_ was sent from Australia to England, and that

the hatching of the eggs was completed after its arrival. The young fed

readily on flies, and we are informed that in the neighbourhood of

Melbourne, where this _Mantis_ is plentiful, specimens are placed by the

citizens on the window-blinds of their houses, so that the rooms may be

cleared from flies by means of the indefatigable voracity of the _Mantis_.

[Illustration: FIG. 147.—_Stenophylla cornigera._ Brazil. (After

Westwood.)]

The geological record as to Mantidae is very meagre and unsatisfactory. The

genus _Mantis_ is said to occur in amber, and Heer has referred to the same

genus an ill-preserved fossil from the upper Miocene beds of Central

Europe; a fragment {259}of a hind wing found in the Jurassic strata of

Siberia has been assigned to the family; and until recently _Lithomantis_

from the Carboniferous beds of Scotland was considered to belong to

Mantidae. Scudder, however, has rejected it therefrom, placing it in the

Neuropteroid division of Palaeodictyoptera, and Brongniart, adding another

species to the genus from the Carboniferous strata in France, proposed to

treat the two as a distinct family, which he called Palaeomantidae.[187]

This naturalist has, however, since renewed his study[188] of these

Insects, has become convinced that they have no relations with existing

Mantidae, and has consequently removed them to the family Platypterides in

the Order Neuroptera.

Six tribes of Mantidae are recognised by Brunner and de Saussure.

Table of the tribes of Mantidae:—

1. Anterior tibiae with the outer edge unarmed beneath or only furnished

with very minute tubercles. (Pronotum not longer than the anterior

coxae.) Tribe 1. AMORPHOSCELIDES. (Fig. 141, _Mantoidea luteola_.)

1′. Anterior tibiae with the outer edge spinose beneath.

2. Anterior femora having the inner edge armed beneath with equal

spines, or with spines in which only the alternate are smaller.

Antennae of the male simple, rarely unipectinate.

3. Tibiae and also the intermediate and hind femora even above.

4. Legs and body with no lobe-like processes. (Antennae simple in

each sex.)

5. Pronotum not forming any dilatation above the insertion of the

coxae, its lateral margins straight or (in the genus

_Choeradodis_) strongly dilated with the anterior margin not

rounded. Tribe 2. ORTHODERIDES. (Fig. 142, _Pyrgomantis_; Fig.

143, _Choeradodis_; Fig. 144, _Eremiaphila turcica_.)

5′. Pronotum dilated above the insertion of the coxae, there with

the lateral margins broadened in a round manner, the anterior

margin rounded. Tribe 3. MANTIDES. (Fig. 140, _Iris oratoria_.)

4′. Legs or body furnished with lobes. (Posterior femora or

segments of the body with lobes, or vertex of the head conically

prolonged.) Tribe 4. HARPAGIDES. (Fig. 136, _Harpax variegatus_;

Fig. 135, _Deroplatys sarawaca_.)

3′. Tibiae as well as the intermediate and hind femora carinate

above. (Pronotum elongate, with the posterior part, behind the

transverse groove, three times as long as the anterior part.) Tribe

5. VATIDES. (Fig. 147, _Stenophylla cornigera_.)

2′. Anterior femora beneath, with the inner edge armed between the

longer teeth with shorter teeth, usually three in number. Antennae of

the male bipectinate. (Vertex conically prolonged.) Tribe 6. EMPUSIDES.

(Fig. 146, _Gongylus gongylodes_.)

{260}CHAPTER XI

ORTHOPTERA _CONTINUED_—PHASMIDAE—WALKING-LEAVES—STICK-INSECTS

FAM. V. PHASMIDAE—STICK AND LEAF INSECTS.

_Head exserted; prothorax small, not elongate; mesothorax very elongate;

the six legs differing but little from one another, the front pair not

raptorial, the hind pair not saltatorial. The cerci of the abdomen not

jointed, consisting of only one piece; the tarsi five-jointed. Tegmina

usually small, or entirely absent, even when the wings are present and

ample. The sexes frequently very dissimilar. Absence of alar organs

frequent._

These Insects are amongst the most curious of natural objects. They are

frequently of large size, some attaining 9 inches in length (Fig. 162,

_Palophus centaurus_, one-half natural length). Their variety of form could

scarcely be surpassed; their resemblance to products of the vegetable

kingdom is frequently very great: some of the more linear species (Fig.

148, _Lonchodes nematodes_) look like sticks or stems of grass; some have a

moss-like appearance, while others resemble pieces of lichen-covered bark.

The members of the tribe Phylliides are leaf-like. A certain number of

other Phasmids are covered with strong spines, like thorns (Fig. 149). The

plant-like appearance is greatest in the female sex. When there is a

difference between the two sexes as to the organs of flight, these are more

fully developed in the male.

{261}[Illustration: FIG. 148.—_Lonchodes nematodes._ Malay Archipelago.

(After Westwood.)]

The antennae are usually many-jointed, but the number of joints varies from

8 to more than 100; the head is exserted; the eyes are more or less

prominent; ocelli are present in some cases. The prothorax is always small,

and it is a remarkable fact that it undergoes but little elongation even in

those species that are most linear and elongate in form (see Fig. 148,

_Lonchodes nematodes_), and that have the meso- and metathoraces extremely

long; it is very simple in structure, consisting apparently merely of a

dorsal and of a sternal plate, nearly the whole of the side being occupied

by the large space in which the coxae are inserted; the edges of the

pronotum are not free. The mesothorax is frequently six times as long as

the prothorax, though in the leaf-like and a few other forms it does not

possess this great extension; still it is always of large size relatively

to the other two thoracic segments. This is peculiar inasmuch as in other

groups where the mesothorax is relatively large there are powerful

mesothoracic wings; whereas the Phasmidae are remarkable for the

obsolescence of the mesothoracic alar appendages. The middle legs and the

tegmina or elytra, when present, are attached only to the posterior part of

the mesothorax; the notum and the sternum are separated by two narrow slips

on each side, the epimeron and episternum. The metathorax is formed like

the mesothorax, except that the posterior part of the dorsal surface is

considered to consist of the first ventral segment consolidated with the

posterior part of the metanotum, the two being distinct enough in the

winged forms. The hind body or abdomen is elongated except in the

Phylliides; it consists of ten dorsal plates; the first frequently looks

like a portion of the metanotum, and is treated as really such by Westwood,

who describes the abdomen as consisting of nine segments. The flat apical

appendages are attached behind the tenth dorsal plate. The ventral plates

are similar to the dorsal in arrangement, except that in the female the

eighth plate forms a sort of spoon-like or gutter-like process to assist in

carrying or depositing the eggs, and that the two following segments are

concealed by it, and are sometimes of more delicate texture. The legs vary

greatly in the details of {262}their shape: the coxae are short, oval, or

round, never large; the trochanter is small; the front femora often have

the basal part narrower than the apical, and they are frequently so formed

that they can be stretched out in front of the head, concealing its sides

and outline and entirely encasing the antennae. There is an arolium or

cushion between the claws of the five-jointed tarsi. The front legs are

frequently longer than the others. Only a very slight study has been made

of the alar organs of Phasmidae; but according to Redtenbacher and Brauer,

they differ greatly from those of Blattidae and Mantidae, inasmuch as the

costal vein is placed not on the actual margin of the wing but in the field

thereof, and in this respect they more resemble the Orthoptera saltatoria.

Very little information exists as to the internal anatomy of the Phasmidae.

Many years ago a memoir of a fragmentary and discursive nature was

published on the subject by J. Müller,[189] but his conclusions require

confirmation; the nervous system, according to his account, which refers to

_Arumatia ferula_, has the anterior ganglia small, the supra-oesophageal

ganglion being apparently not larger than those forming the ventral chain.

[Illustration: FIG. 149.—_Heteropteryx grayi_, male. Borneo. One-half

natural size.]

Joly's more recent memoir on the anatomy of _Phyllium crurifolium_[190] is

also meagre; he states that the nervous system resembles that of the

locusts (Acridiidae), though there are at least ten pairs of ganglia—one

supra-, one infra-oesophageal, three thoracic, and five abdominal. He found

no salivary glands; the Malpighian tubules are slender, elongate, and very

numerous. The tracheal system has no air-vesicles. He found no distinction

{263}of crop and proventriculus, but the true stomach appears to consist of

two different parts, the anterior being remarkably uneven externally,

though destitute of coeca, while on the posterior part there are peculiar

vermiform processes. There are eighteen or twenty tubes in each ovary.

[Illustration: FIG. 150.—_Aschipasma catadromus_, female. Sumatra. Natural

size. (After Westwood.)]

When the young Insect is in the egg, ready for emergence, the meso- and

meta-thorax are not remarkably elongate, so that the femora are not very

far apart, but by the time the creature has fairly emerged from the prison

of its embryonic life the thoracic segments have attained their usual

proportions; much expansion of the body takes place as the Insect leaves

the egg, so that it appears a marvel how it could have been contained

therein; this expansion affects the parts of the body unequally.

The records as to the post-embryonic development of Phasmidae are very

scanty, but indicate great differences in the length of time occupied by

it. _Bacillus patellifer_ is said to moult several times, _Diapheromera

femorata_ only twice. This latter species becomes full grown in six weeks,

while, according to Murray,[191] _Phyllium scythe_ required fifteen or

sixteen months for growth, and did not moult until ten months after

hatching; the number of ecdyses in the case of the _Phyllium_ was three. At

each change of skin an immediate increase in size, similar to that we have

noticed as occurring on leaving the egg, takes place; each limb on being

freed becoming about a fourth longer and larger than the corresponding part

of the envelope from which it has just been withdrawn. After the second

moult of _Phyllium_ the tegmina and wings made their appearance, but

remained of very {264}small size until after the third moult, when they

suddenly shot out to their full size; they came out of little cases about a

quarter of an inch long, and in the course of a few minutes attained their

full size of about two and a half inches of length. In the apterous species

the difference between the young and adults in external characters is very

slight.

[Illustration: FIG. 151.—_Ceroys saevissima._ Brazil. (After Westwood.)]

Phasmidae are very sensitive to cold; both in North America and Australia

their lives are terminated by the occurrence of frost. They are all

vegetable feeders, the cannibalism that has been attributed to them by

several writers being probably imaginary. They are, however, excessively

voracious, so that a pair will destroy a great quantity of foliage; they

are consequently in some parts of the world classed amongst injurious

Insects. In Fiji and the Friendly Islands, _Lopaphus cocophagus_ eats the

cocoa-nut foliage and causes a scarcity of food, so that it becomes a

matter of necessity to destroy these Insects. One writer has gone so far as

to attribute the occurrence of cannibal habits amongst the inhabitants of

some of these islands to the want of food caused by the ravages of this

Insect. Some, if not all, of the Phasmidae have the habit of ejecting a

stinking fluid, that is said to be very acrid, and occasionally, when it

strikes the eye, to cause blindness; this liquid comes from glands placed

in the thorax. Some Phasmidae are much relished as food by birds;

_Diapheromera femorata_ is sucked by several bugs as well as eaten by

birds, and another species is recorded to have harboured Ichneumon-flies in

its body without suffering any apparent inconvenience from their presence

or from their emergence. Notwithstanding the great amount of food they

consume and their want of activity, they produce comparatively few eggs.

From twelve to twenty or thirty is frequently mentioned as about the

{265}number, but in the case of _Diapheromera femorata_ Riley speaks of

upwards of one hundred. These eggs are not deposited in any careful way,

but are discharged at random, simply dropping from the female; the noise

caused by the dropping of the eggs of _Diapheromera femorata_ from the

trees on which the Insects are feeding to the ground is said to resemble

the pattering of raindrops. The eggs of this species often remain till the

second year before they hatch. The eggs in the Phasmidae generally are of a

most remarkable nature, and nearly every one who mentions them speaks of

their extreme resemblance to seeds. Göldi[192] has suggested that this is

for the purpose of deceiving Ichneumons; it is, however, on record that the

eggs are actually destroyed by Ichneumons. It is worthy of notice that the

eggs are shed like seeds, being dropped loosely and, as we have said,

remaining on the ground or elsewhere, sometimes for nearly two years,

without other protection than that they derive from their coverings. Each

egg is really a capsule containing an egg, reminding us thus of the capsule

of the Blattidae, which contains, however, always a number of eggs. Not

only do the eggs have a history like that of seeds, and resemble them in

appearance, but their capsule in minute structure, as we shall subsequently

show, greatly resembles vegetable tissue. The egg-capsule in Phasmidae is

provided with a lid, which is pushed off when the Insect emerges (Fig.

157). This capsule induced Murray to suppose that the egg contained within

is really a pupa, and he argued therefrom that in the Orthoptera the larval

stages are passed in the egg, and that the Insect after its emergence

should be looked on as an active pupa that takes food.

[Illustration: FIG. 152.—Eggs of Phasmidae: A, _Lonchodes duivenbodi_; B,

_Platycrania edulis_; C, _Haplopus grayi_; D, _Phyllium siccifolium_.

(After Kaup.)]

The individuals of this group of Insects possess the power of reproducing a

lost limb; and Scudder, who has made some experiments as to this,[193]

states that if a leg be cut off beyond the {266}trochantero-femoral

articulation, the parts remaining outside of this joint are dropped before

the next moult, and are afterwards renewed either as a straight short stump

in which the articulations are already observable, or as a miniature leg,

the femur of which is straight and the tibia and tarsus curved into a

nearly complete circle; in the former case, the leg assumes at the next

moult the appearance that it has in the second case; this latter form is

always changed at the succeeding moult into a leg resembling the normal

limb in every respect excepting size, and the absence of the fourth tarsal

joint (Fig. 153). If the leg be removed nearer to the body than the

trochantero-femoral articulation the limb is not replaced.

The sexes are frequently extremely different; the female is usually very

much larger than the male. This latter sex often possesses wings when they

are quite wanting in the other sex; the resemblance to portions of plants

is often very much greater in the female than it is in the male.

[Illustration: FIG. 153.—_Cyphocrania aestuans_; individual in which the

right front leg has been renewed. Senegal. (After Westwood.)]

We have pointed out that the tegmina or upper wings are usually of small

size or absent (Fig. 150, _Aschipasma catadromus_), even in the species

where the lower wings are very largely developed; in such cases the latter

organs are folded in a complicated, fan-like manner, and repose on the

back, looking as if they were really the tegmina (Fig. 159, _Calvisia

atrosignata_); this appearance, moreover, is in some species enhanced much

by the fact that the part of the wing which is outermost in the folded

state is quite differently {267}coloured from the rest of the organ. The

colour of the body in many Phasmidae is said to be very variable, and if

the tints be owing to chlorophyll or other plant juices, finding their way

amongst the Insect-tissues, this is readily understood; in _Diapheromera_

the young Insect is brownish on hatching, becomes green after feeding, and

turns brown again when the leaves do so. The ocelli, too, are said to be

very variable, and M‘Coy goes so far as to state[194] that they may be

either present or absent in different individuals though of the same

species and sex,—a statement so remarkable as to require minute

examination, though it is to some extent confirmed by the remarks of other

entomologists.

[Illustration: FIG. 154.—_Phyllium scythe_, female. Sylhet. (After

Westwood.)]

The resemblance presented by different kinds of Orthoptera to leaves is so

remarkable that it has attracted attention even in countries where Natural

History is almost totally neglected; in many such places the inhabitants

are firmly convinced that the Insects are truly transformed leaves, by

which they understand a bud developing into a leaf and subsequently

becoming a walking-leaf or Insect. To them the change is a kind of

metamorphosis of habit; it grew as a leaf and then took to walking.[195] It

is usually the tegmina that display this great resemblance to vegetable

structures, and there is perhaps no case in which the phenomenon is more

marked than it is in the genus _Phyllium_, the members of which occur only

in the tropical regions of the Old World, where they extend from Mauritius

and the Seychelles to the Fiji Islands—possibly even more to the East—and

have, it would appear, a peculiar penchant for insular life.

{268}[Illustration: FIG. 155.—_Phyllium scythe_, male. Sylhet. (After

Murray.)]

The genus _Phyllium_ constitutes by itself the tribe Phylliides. Although

the characters and affinities of this group have been only very

inadequately investigated, it will probably prove to be a very distinct and

isolated one. The species are not well known, but are probably numerous,

and the individuals are believed not to be rare, though the collections of

entomologists are very badly supplied with them. The resemblance of the

tegmina or front wings to leaves is certainly of the most remarkable

nature. During the early life the Insect does not possess the tegmina, but

it is said then to adapt itself to the appearance of the leaves it lives

on, by the positions it assumes and the movements[196] it makes. When

freshly hatched it is of a reddish-yellow colour. The colour varies at

different periods of the life, but "always more or less resembles a leaf."

After the young Insect has commenced eating the leaves it speedily becomes

bright green; and when the metamorphosis is completed the female Insect is

possessed of the leaf-like tegmina shown in Figs. 154, 156. Before its

death the specimen described by Murray passed "through the different hues

of a decaying leaf." Brongniart has had opportunities of observing one of

these leaf-Insects, and has, with the aid of M. Becquerel, submitted their

colouring matter to spectral analysis,[197] with the result of finding

{269}that the spectrum exhibits slight distinctions from that of solutions

of chlorophyll, but does not differ from that of living leaves. Mr. J. J.

Lister when in the Seychelles brought away living specimens of _Phyllium_;

and these becoming short of food, nibbled pieces out of one another just as

they might have done out of leaves. The Phasmidae are purely vegetable

feeders, and these specimens did not seriously injure one another, but

confined their depredations to the leaf-like appendages and expansions.

The males of this genus are totally different from the females; the

foliaceous tegmina being replaced by appendages that are not leaf-like,

while the posterior wings, which are large and conspicuous parts of the

body, have no leaf-like appearance (Fig. 155).

[Illustration: FIG. 156.—Alar organs and one side of thorax of _Phyllium

crurifolium_: A, tegmen; B, rudiment of wing; C, pronotum; D, anterior

division of mesonotum; E, posterior division; F, metanotum; _a_, _b_, _c_,

_d_, _e_, chief wing-nervures; _a_, mediastinal; _b_, radial; _c_, ulnar;

_d_, dividens?; _e_, plicata?.]

In the female _Phyllium_ the hind wings are not present, being represented

by a minute process (Fig. 156, B). The tegmen of the female _Phyllium_ is,

from various points of view, a remarkable and exceptional structure. It is

the rule that when there is in Insects a difference between the alar organs

of the two sexes it is the male that has them largest; this is the case in

_Phyllium_ so far as the hind wings are concerned, but in the fore-wings

the rule is departed from, the leaf-like tegmina of the female being very

much larger than the rudimentary wing-covers of the male. In Phasmidae it

is the rule that the tegmina are atrophied, even when the hind wings are

largely developed. This is the case in the male of _Phyllium_, but in the

female this normal condition is reversed. Although the alar organs of

Phasmidae have received hitherto but a small amount of attention, it is

probable that the female tegmen of _Phyllium_ is as peculiar

morphologically as it is in other respects. In Fig. 156 we give an accurate

representation of the chief nervures in the tegmen of a female _P.

crurifolium_. It is interesting to compare this with the diagrams we give

of the tegmina of a Blattid (Fig. 121) and of an Acridiid {270}(Fig. 167);

the tegmen of the _Phyllium_ is very different, the radial vein and all the

parts behind it being placed quite close to the posterior edge of the

structure. A similar view is taken by both Redtenbacher and Brauer. The

latter says,[198] "In _Phyllium_ (the walking-leaf) almost the whole of the

front wing is formed by the praecostal and subcostal fields; all the other

fields with their nervures, including even the costa, are compressed

towards the hind margin into a slender stripe. In the hind wing the costa

is, however, marginal." Unfortunately no examination appears to have been

made of the male tegmen, so that we do not know whether that of the female

differs from it morphologically as strongly as it does anatomically. It is,

however, clear that the tegmina of the female _Phyllium_ not only violate a

rule that is almost universal in the Insecta, but also depart widely from

the same parts of its mate, and are totally different—and, for a Phasmid,

in an almost if not quite unique fashion—from the other pair of alar organs

of its own body.

[Illustration: FIG. 157.—Egg of _Phyllium scythe_. (After Murray.) A, The

whole egg, natural size; A', magnified; B, the capsule broken, showing the

true egg inside, natural size; B', magnified.]

{271}[Illustration: FIG. 158.—Portion of a longitudinal section of the egg

capsule of _Phyllium crurifolium_: _a_, external; _b_, middle; _c_, inner

zones; _d_, elongate alveoli. × 100. (After Henneguy.)]

We have already alluded to the resemblance to seeds displayed by the eggs

of Phasmidae. The eggs of _Phyllium_ have been studied by several

entomologists, and their resemblance to seeds excites general astonishment.

Murray describes the egg-capsule of _Phyllium scythe_, and says: "It looks

uncommonly like some seeds; if the edges of the seed of _Mirabilis jalapa_

were rubbed off, the seed might be mistaken for the egg. The ribs are all

placed at equal distances, except two, which are wider apart, and the space

between them flatter, so that on the egg falling it rolls over till it

comes to this flatter side, and there lies.... At the top there is a little

conical lid, fitting very tightly to the mouth.... On removing the lid we

see a beautiful porcelain chamber of a pale French-white colour, bearing a

close resemblance to the texture of a hen's egg, but it is not calcareous,

and has more the appearance of enamel." The eggs of _P. crurifolium_ have

been examined by Joly and Henneguy; their account confirms that of Murray.

Henneguy adds that a prominent lozenge on the egg represents the surface by

which the achene of an umbelliferous plant is united to the column, and

that the micropyles are placed on this lozenge. The minute structure of the

capsule has also been examined by several entomologists; and Henneguy,[199]

who has described and figured some of the details of the capsule of _P.

crurifolium_, says, "Almost every botanist, on examining for {272}the first

time a section of this capsule, would declare that he is looking at a

vegetable preparation."

We may remark that, although there is difference of opinion on the point,

the evidence extant goes to show that the egg-capsules are formed in the

egg-tubes, only one egg being produced at a time in a tube,[200] the others

in it remaining quite rudimentary.

About 600 species of the family are known; there are only four or five

kinds found in Europe, and they are all confined to the south, only one of

them extending as far north as Central France. The males of these European

_Bacilli_ are extremely rare in comparison with the females, which are

common Insects. Phasmidae are of almost universal distribution in the warm

parts of the world, and even the species whose individuals are of large

size seem to be able to continue their existence in comparatively small

islands. Australia is perhaps the region where they are most largely

developed at present. Macleay says of _Podacanthus wilkinsoni_ that it is

rare in any part of Australia to find in the summer season a gum-tree

without a few of these Insects grazing on it; and occasionally this Insect

has been so abundant there that the trees for miles around have been

denuded of their foliage by it, and the dead and dying Insects have been

found lying beneath the trees almost in heaps. There are several Phasmidae

in New Zealand, all wingless forms, and different from those found in

Australia. In Brazil a species of the genus _Prisopus_ has the peculiar

habit of seeking shelter under the stones submerged in the mountain

streams; to enable it to do this it is remarkably constructed, the under

side of the body being hollowed, and various parts set with a dense fringe

of hairs; the Insect is supposed to expel the air from the body in order to

adhere to the upper surface of a stone, where it sits with its fore legs

extended in front of its head, which is directed against the current.

Attention has been called to a still more remarkable form said to be allied

to the Prisopi, by Wood-Mason,[201] who calls the Insect _Cotylosoma

dipneusticum_. This Insect is apparently known only by a single example of

the female sex; it is 3 or 4 inches in length, has rudimentary organs of

flight, and along the lower margins of the metathorax there are said to be

on each side five {273}conspicuous fringed plates of the nature of tracheal

gills; these coexist with open stigmata for aerial respiration, as in the

imago of _Pteronarcys_. The writer has examined this curious Insect, and

thinks it very doubtful whether the plates are branchiae at all. The

locality for this Insect is the island of Taviuni, not Borneo, as stated by

Wood-Mason. These and one or two Acridiidae are the only Insects of the

Order Orthoptera at present believed to possess aquatic habits.

[Illustration: FIG. 159.—_Calvisia atrosignata_, female. Tenasserim. (After

Brunner.)]

Although the number of species of Phasmidae is small in comparison with

what we find in many of the large families of Insecta, yet there is

probably no other family that equals it in multiplicity of form and

diversity of external appearance.

{274}[Illustration: FIG. 160.—_Eurycantha_ (_Karabidion_) _australis_,

male. Lord Howe's Island. (After Westwood.)]

[Illustration: FIG. 161.—_Anisomorpha pardalina._ Chili. (After Westwood.)]

_Karabidion_ (Fig. 160), a genus found in some of the islands of the

southern hemisphere, has the hind legs enormously thickened in the male.

Some Phasmids, e.g. _Orxines zeuxis_, have the hind wings marked and

coloured after the manner of butterflies or moths. _Lamponius laciniatus_

has an elaborately irregular outline, looking like a mass of moss, and some

species of _Bacteria_ are so very slender that the linear body is scarcely

equal in size to one of the legs it bears. Among the most interesting forms

are the Insects for which the genera _Agathemera_ and _Anisomorpha_ (Fig.

161) have been established; they are remarkably broad and short, have the

mesothorax but little elongated, with the tegmina attached to it in the

form of two short, thick, leathery lobes; while the wings are seen as marks

on the metanotum looking like a mere sculpture of the surface; these

Insects {275}have quite the appearance of larval forms, and it is worthy of

note that the elongation of the mesothorax, which is one of the most marked

features of the Phasmidae, is in these forms only very slight.

[Illustration: FIG. 162.—_Palophus centaurus._ Old Calabar. Half natural

size. (After Westwood.[202])]

{276}[Illustration: FIG. 163.—_Titanophasma fayoli._ Carboniferous

formation at Commentry. × ⅕. (From Zittel.)]

[Illustration: FIG. 164.—_Titanophasma fayoli_ (restoration). × ⅒.]

Some Insects said to belong to the genera _Phasma_ and _Bacteria_ have been

found in amber. A single Insect-fossil found in the Tertiary strata in

North America has recently been referred by Scudder to the family, and even

to a genus still existing in the New World—_Agathemera_; the fragment is,

however, so defective, and the characteristic points of the Phasmidae are

so little evident in it, that not much reliance can be placed on the

determination. No Phasmid has been unearthed from Mesozoic strata, so that,

with the exception of the fragment just mentioned, nothing that evidently

belongs to the Phasmidae has been discovered older than the remains

preserved in amber. In the Carboniferous layers of the Palaeozoic epoch

there are found remains of gigantic Insects that may possibly be connected

with our living Phasmidae. These fossils have been treated by Brongniart

and Scudder as forming a distinct family called Protophasmidae. The first

of these authors says[203] that our Phasmidae were represented in the

Carboniferous {277}epoch by analogous types differing in the nature of the

organs of flight: these ancient Insects were of larger size than their

descendants, being 25 to 50 centimetres long, and as much as 70 in spread

of wing. To this group are referred, on somewhat too inferential grounds,

the fossil wings found in the Carboniferous layers, and called by

Goldenberg _Dictyoneura_.

We reproduce from Zittel's handbook a figure (Fig. 162) of one of these

gigantic Insects, and add an attempt at a restoration of the same after the

fashion of Scudder (Fig. 163). From these figures it will be seen that the

relation to our existing Phasmidae must at best have been very remote.[204]

It will be noted that the larger of the two figures is on a ⅕ scale.

The classification of Phasmidae was left in a very involved state by Stål,

but has recently been brought into a more satisfactory condition by Brunner

von Wattenwyl. We give a translation of his table of the tribal

characters:—

1. Tibiae beneath carinate to the apex, without an apical area.

2. Antennae much longer than the front femora, many jointed, the joints

being above 30 in number and only distinct at the base and towards the

apex.[205]

3. Median [true first abdominal] segment much shorter than the

metanotum.[206] The species all apterous.

4. The anal segment of the males roof-like, more or less bilobate.

The female has a supra-anal lamina. The species inhabit the Old

World. Tribe 1. LONCHODIDES (Fig. 148, _Lonchodes nematodes_.)

4′. The anal segment of the males arched, straight behind. No

supra-anal lamina in the female. The species are American. Tribe 2.

BACUNCULIDES.

3′. Median segment as long as, or longer than the metanotum. Species

with the male or both sexes winged.

4. Females apterous or rarely possessed of short wings.[207] Males

winged. Femora dentate beneath, or lobed, or at least armed with

one tooth. Species occur both in America and in the Old World.

Tribe 3. BACTERIIDES. (Fig. 162, _Palophus centaurus_.) {278}4′.

Each sex winged. Femora smooth beneath. The species belong to the

Old World. Tribe 4. NECROSCIDES. (Fig. 159, _Calvisia

atrosignata_.)

2′. Antennae (at any rate in the females) shorter than the front

femora, the joints distinct, not more than 28 in number. The species

belong to the Old World.

3. Median segment shorter than the metanotum. Apterous species. Cerci

plump. Tribe 5. CLITUMNIDES. (Fig. 160, _Eurycantha australis_.)

3′. Median segment longer than the metanotum. Species usually winged.

Cerci (except in some genera of the group _Platycraninae_) flattened,

elongate. Tribe 6. ACROPHYLLIDES. (Fig. 153, _Cyphocrania aestuans_.)

1′. Tibiae furnished beneath with a triangular apical area.

2. Antennae many jointed, longer than the front femora.

3. Median segment shorter than the metanotum. Apterous species.[208]

4. Either head, thorax, or legs spiny or lobed. Tribe 7.

CLADOMORPHIDES. (Fig. 149, _Heteropteryx grayi_.)

4′. Head, thorax and legs unarmed. Tribe 8. ANISOMORPHIDES. (Fig.

161, _Anisomorpha pardalina_.)

3′. Median segment longer than the metanotum.

4. Claws unarmed. Tegmina lobe-like, either perfectly developed or

entirely absent. The winged species are all American, the apterous

are both African and Australian. Tribe 9. PHASMIDES.

4′. Claws toothed on the inner side. Tegmina spine-like. Wings well

developed. The species are Asiatic. Tribe 10. ASCHIPASMIDES. (Fig.

150, _Aschipasma catadromus_.)

2′. Antennae shorter than the anterior femora,[209] formed of not more

than 20 joints. Old World species.

3. Body slender. Apterous. Tribe 11. BACILLIDES.

3′. Body very broad, lamina-like. Either wings or tegmina present.

Tribe 12. PHYLLIIDES. (Fig. 155, _Phyllium scythe_, male; Fig. 154,

_idem._, female.)

{279}CHAPTER XII

ORTHOPTERA _CONTINUED_—ACRIDIIDAE

FAM. VI. ACRIDIIDAE—LOCUSTS AND GRASSHOPPERS.

_Orthoptera with the hind legs differing from the others by being more

elongate and having their femora broader near the base. Antennae short,

with less than 30 joints. No exserted ovipositor in female. Tarsi short,

with three distinct joints. The auditory organ placed on the side of the

upper part of the first abdominal segment._

[Illustration: FIG. 165.—_Tryxalis nasuta_, female. Natural size. Europe.]

We commence the consideration of the saltatorial Orthoptera with the family

Acridiidae. It includes the grasshoppers of our native fields as well as

the destructive migratory locusts of foreign countries, and is the most

numerous in species and individuals of any of the Orthopterous families.

Our native grasshoppers, though of small size, give a very good idea of the

Acridiidae. Active little Insects, with large head, conspicuous {280}eyes,

laterally somewhat compressed body, long hind legs with femur directed

upwards and backwards, the knee-joint forming an acute angle, the organs of

flight pressed to the sides of the body, our common grasshoppers represent

the Acridiidae quite as truly as do the gigantic exotic forms, some of

which measure 9 or 10 inches across the expanded wings.

[Illustration: FIG. 166.—Front of head of _Porthetis_ sp. Transvaal.]

The large head is immersed behind in the thorax; the front is deflexed, or

even inflexed, so as to be placed in a plane at an acute angle with that of

the vertex (Fig. 165); the compound eyes are placed at the sides of the

head and rather widely separated; in front there are three small ocelli.

Two of these are placed one on each side close to the eye between the eye

and the base of the antenna; the third ocellus being in the middle just in

front of the insertion of the antennae, between the edges of the margined

space that usually runs down the middle of the front. The positions of

these ocelli and the shape of the front and upper parts of the head are of

importance in the classification of the family; the ocelli vary much in

their development, being in some species beautifully clear and prominent

(Fig. 166), while in others they are small, not easily detected, apparently

functionally imperfect. The antennae are never very long, are sometimes

compressed and pendent from the front of the head. The parts of the mouth

are very large. The prothorax is much arched; it is often carinate or

crested along the middle of the notum; this part is frequently prolonged

backwards, forming a sort of hood over the base of the wings; the surface

may be rugged or warty, forming in some species inexplicable structures;

the legs are widely separated, all of them being placed at the sides of the

body; the edge of the pronotum is distinct and situate close to the base of

the leg; the prosternum frequently bears a large projection extending

directly downwards between the front legs. The mesothorax is short, its

chief sternal piece is very broad, the middle legs being very widely

separated. The metathorax is larger; its sternal plate usually exhibits

behind a sort of embrasure filled up by a portion of the first ventral

plate.

{281}[Illustration: FIG. 167.—Alar organs of Acridiidae (_Bryodema

tuberculata_). A, Left tegmen; B, left wing: _ar.med_, area mediastina;

_ar.sc_, area scapularis; _ar.disc_, area discoidalis; _ar.an_, anal area;

_v.m_, vena mediastina; _v.r_, vena radialis; _v.r.a_, vena radialis

anterior; _v.r.m_, vena radialis media; _v.r.p_, vena radialis posterior;

_v.i_, vena intercalata; _v.u.a_, vena ulnaris anterior; _v.u.p_, vena

ulnaris posterior; _v.d_, vena dividens; _v.pl_, vena plicata. (After

Brunner.)]

The hind body is elongate, and shows distinctly eight dorsal segments,

behind which are the pieces forming—in the female, the fossorial organs

which replace an ovipositor—in the male, the modified parts connected with

the terminal segment. The alar organs (Fig. 167) exhibit, according to

Brunner, the same areas as we have described in Blattidae. According,

however, to Redtenbacher[210] the tegmina of the Acridiidae and other

saltatorial Orthoptera differ from those of the cursorial group (with the

exception of the Phasmidae) in that they possess a praecostal field, due to

the fact that the vein which in the Cursoria is costal, _i.e._ forms the

front margin, in the Saltatoria lies, on the contrary, in the field of the

wing. If this view be correct the mediastinal area of Brunner is not

homologous in the two divisions. The tegmina are long and comparatively

narrow; they are of firm parchment-like texture, with several longitudinal

veins, which divide beyond the middle, so as to become more numerous as

they reach the extremity of the wing; there is much reticulation, dividing

the surface into numerous small cells. The hind wings are much more ample,

and of more delicate texture; the longitudinal veins fork but little, the

numerous cross veinlets are fine. In repose the hind wings fold together in

a fan-like manner, and are entirely concealed by the upper wings. The front

and middle legs are similar and small, the coxae are quite small, and do

not completely fill the articular cavities, which are partly covered by

membrane; all the tarsi are three-jointed. The basal joint, when looked at

beneath, is seen to bear three successively placed pads, so that from

beneath the tarsi look as if they were five-jointed {282}(Fig. 185, C). The

hind legs are occasionally very long; their femora, thicker towards the

base, are generally peculiarly sculptured, bearing longitudinal ridges or

grooves, which are more or less spinose, and are also very frequently

marked with short parallel lines meeting a central longitudinal line at

similar angles, so as to give rise to a well-marked pattern; where the legs

are broader the pattern is more complex (Fig. 168). The long tibiae bear

two rows of spines on their upper or posterior edge; this part of the hind

leg can be completely bent in under the femur. The stigmata consist of one

prothoracic, one metathoracic, and eight abdominal pairs.

[Illustration: FIG. 168.—Hind leg of _Porthetis_ sp. Transvaal.]

In reference to the ocelli, which are shown in Fig. 166, we may remark that

the Acridiidae is one of the large groups of Insects in which the

coexistence of compound and single eyes is most constant, though in some of

the wingless forms the ocelli are very imperfect. We know at present of

nothing in the habits of Acridiidae to render two kinds of eyes specially

necessary. We shall subsequently see that a similar condition in regard to

the function of hearing is believed to exist in this family.

Acridiidae are remarkable amongst the Orthoptera for the possession of air

sacs or vesicular dilatations in the interior of the Insect in connexion

with the tracheae (Fig. 176). Such vesicles are found in many of the higher

winged Insects, but not in larval forms, or in those that are destitute of

powers of flight.[211] They, no doubt, assist the Insect in its movements

in the air. The body of a large grasshopper or locust is naturally of

considerable weight, and it is more than probable that true flight can only

be accomplished when these vesicles are dilated and filled with air. The

exact mode in which the sacs are dilated is not known; possibly it may be

accomplished by the elasticity of the structure of the vesicles coming into

action when the other contents of the {283}body are not completely

developed, or are temporarily diminished. Although air vessels are absent

in the neighbouring groups of Orthoptera, Dufour says they are present even

in apterous forms of Acridiidae, but he gives no particulars.[212] Packard

has given an account[213] of the arrangement of these remarkable sacs in

the Rocky Mountain Locust. He finds that there are two sets: a thoracic

group, consisting of a pair of very large size, with which are connected

some smaller sacs placed in the head; and an abdominal set, which forms a

very remarkable series. The figures we give (Fig. 176, A, B) show that

these sacs are of such large size that if fully distended they must

interfere with the development of the ovaries, and that they must be

themselves greatly diminished, if not obliterated, by the distension of the

alimentary canal. We may look on them as only coming into full play when

the normal distension of the canal is prevented, and there is only small

development of the reproductive organs. Under such circumstances the locust

becomes a sort of balloon, and migrates. In addition to the air sacs there

are many dilatable tracheae, placed chiefly in parts of the body where

there is not space for the large air sacs. These are, for the sake of

clearness, omitted from our figure.

The ganglia constituting the brain are simpler in Acridiidae than they are

in the higher Insects, such as bees and wasps, and have been specially

studied by Packard[214] and Viallanes.[215] The other ganglia of the

nervous cord are eight in number, three thoracic and five abdominal.

[Illustration: FIG. 169.—Ovaries of _Oedipoda caerulescens_: _a_, calyx;

_b_, its gut-like appendage; _c_, sebific gland; _d_, termination of body.

(After Dufour.)]

The salivary glands are small. The alimentary canal is capacious but not

coiled. It has no gizzard, but the crop has a peculiar structure,

apparently as a substitute. There are diverticula connected with the true

stomach. The Malpighian tubes are elongate {284}and extremely numerous. The

pair of testes is united in a single envelope. The form and arrangement of

the ovaries is remarkable (Fig. 169); the egg-tubes are united by the

convergence of their terminal threads into a single mass; outside of each

ovary there extends a large calyx, into which the tubes open; each calyx is

prolonged at its extremity, and forms a long, convoluted tube.

[Illustration: FIG. 170.—Inner face of femur of _Stenobothrus_, male,

showing line, _a-a_, of musical beads. (After Landois, magnified three

times.)]

Acridiidae possess structures for the production of sound, together with

others that are, no doubt, for hearing. The chirping of grasshoppers is

accomplished by rubbing together the outer face of the upper wing and the

inner face of the hind femur. This latter part bears a series of small

bead-like prominences placed on the upper of the two lower ridges that run

along the side that is nearest to the body (Fig. 170); the tegmen or

wing-case has projecting veins, one of which is slightly more prominent,

and has a sharp edge; by scraping this edge over the beads of the femur the

wing is thrown into a state of vibration and a musical sound is produced.

The apparatus for producing sound was for long supposed to be confined to

the male sex of grasshoppers; it was indeed known that females made the

movements appropriate for producing music, but as they appeared to be

destitute of instruments, and as no sound was known to follow from their

efforts, it was concluded that these were merely imitative. Graber has,

however, discovered[216] that rudimentary musical organs do exist in the

females of various species of _Stenobothrus_ (Fig. 171, B). It is true that

in comparison with those of the male (Fig. 171, A) they are minute, but it

would appear that they are really phonetic, though we can hear no sounds

resulting from their use.

[Illustration: FIG. 171.—A, Some of the knobs projecting from the surface

of the femur of _Stenobothrus melanopterus_, male; B, same of the female.

Highly magnified. (After Graber.)]

Graber considers that the musical pegs of Acridiidae are {285}modified

hairs, and he states that in certain females the stages intermediate

between hair and peg can be found. There is apparently much variety in the

structure of these instruments in different species, and even in

individuals of the same species. In _Stenobothrus lineatus_, instead of

pegs, the instrument consists of raised folds.

In some of the aberrant forms of Acridiidae—certain Eremobiides and

Pneumorides—the males are provided with sound-producing instruments

different to those we have described, both as regards situation and

structure.

[Illustration: FIG. 172.—Middle of body of _Pachytylus nigrofasciatus_, to

show tympanum, _e_. (After Brunner.)]

[Illustration: FIG. 173.—Mecostethus grossus: A, Insect with wings

expanded; B, profile of head and prothorax. (After Brunner.)]

If the dorsal aspect of the first segment of the hind body of an Acridian

Insect be carefully examined there may be seen in the majority of species

an organ which has somewhat the appearance of an ear (Fig. 172), and which

there is great reason for believing to be really an organ of that nature.

It is situate a little over the articulation of the hind leg, very close to

the spot where the sound is, as above described, produced. There are three

forms of these Acridian ears as described by Brunner:[217] (1) a membrane

surrounded by a rim; (2) the membrane somewhat depressed, a portion of the

segment projecting a little over it; (3) the depression very strongly

marked, and the sides projecting over it so much that all that is seen

externally is a sort of broad slit with a cavity beneath it. This last is

the condition in which the ear exists in the genera _Mecostethus_ (Fig.

173) and _Stenobothrus_, which are among our few native grasshoppers. On

minute examination this ear proves to consist of a tympanum supplied

internally with nerve and ganglion in addition to {286}muscles, and

tracheal apparatus of a complex nature; it is no doubt delicately sensitive

to some forms of vibration. Unlike the stridulating organ, these ears exist

in both sexes; they are found in a great majority of the species of

Acridiidae. The forms in which the ears are absent are usually at the same

time wingless and destitute of organs of stridulation; but, on the other

hand, there are species—some of them wingless—that are, so far as is known,

incapable of stridulation and yet possess these ears.

It is, indeed, a matter of great difficulty to decide as to the exact

function of these ear-like acoustic organs, which, we may remind the

reader, are peculiar to the saltatorial Orthoptera, and we must refer for a

full discussion of the subject to Graber's masterly works,[218] contenting

ourselves with a brief outline, which we may commence by saying that the

Orthoptera with ears are believed to be sensitive to sounds by means other

than these organs. This suggests that the latter exist for some purpose of

perception of special sound. But if so what can this be? Only the males

possess, so far as we know, effective sound-producing organs, but both

sexes have the special ears; moreover, these structures are present in

numerous species where we do not know of the existence of phonetic organs

in either sex. Thus it appears at present impossible to accept these organs

as being certainly special structures for the perception of the music of

the species. It is generally thought that the females are charmed by the

music of the males, and that these are stimulated to rivalry by the

production of the sounds; and Dufour[219] has suggested that this process

reacts on the physiological processes of the individual. There has not been

a sufficient amount of observation to justify us in accepting these views,

and they do not in any way dispose of the difficulty arising from the

existence of the acoustic organs in species that do not, so far as we know,

produce special sounds. It is possible that the solution of the difficulty

may be found in the fact that these apparently dumb species do really

produce some sound, though we are quite ignorant as to their doing so. It

is well known that sounds inaudible to some human ears are perfectly

distinct to others. Tyndall, in his work on Sound, has illustrated this by

a fact that is of special interest from our present point of view.

"Crossing {287}the Wengern Alp with a friend," he says, "the grass on each

side of the path swarmed with Insects which to me rent the air with their

shrill chirruping. My friend heard nothing of this, the Insect world lying

beyond his limit of audition." If human ears are so different in their

capacities for perceiving vibrations, it of course becomes more probable

that auditory organs so differently constituted as are those of Insects

from our own may hear sounds when the best human ear can detect nothing

audible. On the whole, therefore, it would appear most probable that the

Orthoptera provided with acoustic organs, and which we consider dumb, are

not really so, but produce sounds we cannot hear, and do so in some manner

unknown to us. If this be the case it is probable that these ears are

special organs for hearing particular sounds.

Scudder, who has given considerable attention to the subject of Orthopteran

music, says that in N. America "the uniformity with which each species of

_Stenobothrus_ plays its own song is quite remarkable. One kind,

_Stenobothrus curtipennis_, produces about six notes per second, and

continues them from one and a half to two and a half seconds; another, _S.

melanopleurus_, makes from nine to twelve notes in about three seconds. In

both cases the notes follow each other uniformly, and are slower in the

shade than in the sun."

Some of the species of Acridiidae, it should be noticed, produce a noise

during their flights through the air, due to the friction of the wings;

whether this has a definite importance, or whether it may be entirely

incidental, has scarcely yet been considered.

Information of a satisfactory kind as to the post-embryonic development of

the Acridiidae is but scanty. We have represented in Fig. 84, A, the

condition in which a migratory locust, _Schistocerca peregrina_, leaves the

egg, and we will here complete the account of its growth; following

Brongniart,[220] whose statement is confirmed by Lestage and other

naturalists. Immediately on leaving the egg the young locust casts its

skin, and is then of a clear green colour, but it rapidly becomes brown,

and in twelve hours is black. At this early age the gregarious instinct,

possessed by this and some other species of Acridiidae, becomes evident. In

six days the individual undergoes a second moult, after which it is black,

spotted and banded with white, and with a rose-coloured streak on each side

of the hind body. The {288}third ecdysis occurs in six or eight days after

the second; the rose colour becomes more distinct, and the head is of a

brown tint instead of black. After eight days the fourth ecdysis occurs;

the creature is then about 35 millimètres long; its colour has much

changed, the position of the markings is the same, but the rose colour is

replaced by citron yellow, the line of the spiracles is marked with white,

and at this time the creature has the "first rudiments of wings," and is

very voracious. In ten days another ecdysis takes place, the yellow colour

is more vivid, the prothorax is definitely speckled with white, and the

hind body is increasing much in size. In fifteen or twenty days the sixth

moult occurs, and the Insect appears in its perfect form; the large tegmina

now present are marked with black in the manner so well known, and the

surface generally is variegated with bluish and rosy marks. Although this

is the colour in Algeria, yet apparently it is not so farther south; the

Insects that arrive thence in the French colony are on some occasions of a

different colour, viz. reddish or yellowish, those of this latter tint

being, it is believed, older specimens of the reddish kind. M. Brongniart

points out that some Phasmidae—of the _Phyllium_ group—undergo an analogous

series of colour-changes in the course of the individual development,

though other species do not.

[Illustration: FIG. 174.—Development of wings in _Caloptenus spretus_: the

upper row gives a lateral view of the thoracic segments, and the lower row

a dorsal view of these segments; 1, second instar; 2, third instar; 3,

fourth instar; 4, fifth instar. (After Riley.) _t_, tegmen; _w_, wing.]

{289}[Illustration: FIG. 175.—_Caloptenus spretus._ North America. A, Newly

hatched, much magnified; B, adult, natural size. (After Riley.)]

Riley and Packard have given an account[221] of some parts of the

post-embryonic development of the Rocky Mountain Locust, which enables us

to form a satisfactory conception of the stages of development of the

wings. Fig. 175, A, represents the first instar, the young locust, just

emerged from the egg and colourless. Fig. 174 shows some of the subsequent

stages of development of the wings, the upper line of figures giving a

profile view of the thoracic segments, and the lower line showing their

dorsal aspects; 1 shows the condition of the parts in the second instar,

the chief difference from the first instar being the development of colour;

in the third instar there is an evident slight development of the future

alar organs, exhibited chiefly in the outgrowth and lobing of the free

posterior angles of the meso- and metanota, as shown in Fig. 174, 2. After

the third moult there is a great difference; the instar then disclosed—the

fourth—has undergone a considerable change in the position of the meso- and

metathoraces, which are thrust forward under the pronotum; this has become

more enlarged and hood-like (Fig. 174, 3); at the same time the

wing-rudiments have become free and detached, the metathoracic pair being

the larger, and overlapping the other pair. The fifth instar (Fig. 174, 4)

differs but little from the fourth, except in the larger size of the

pronotum and wing-rudiments. The sixth—shown in Fig. 175, {290}B—is the

perfect Insect, with the alar organs free and large, the prothorax much

changed in form, the colour different. From the above it will be seen that

the chief changes occurred at the third and fifth ecdyses, after each of

which a considerable difference in the form of the Insect was revealed. In

the first three instars the sexes can scarcely be distinguished, in the

fourth they are quite distinct, and in the fifth coupling is possible,

though usually it does not occur till the final stage is attained.

The discovery that Orthoptera change their colours in the course of their

development, and even after they have become adult, is important, not only

from a physiological point of view, but because it throws some light on the

questions as to the number of species and the geographical distribution of

the migratory locusts, as to which there has existed a great confusion.

The Acridiidae are considered to be exclusively vegetable feeders, each

individual consuming a very large quantity of food. The mode in which the

female deposits her eggs has been described by Riley,[222] and is now

widely known, his figures having been frequently reproduced. The female has

no elongate ovipositor, but possesses instead some hard gonapophyses

suitable for digging purposes; with these she excavates a hole in the

ground, and then deposits the eggs, together with a quantity of fluid, in

the hole. She prefers hard and compact soil to that which is loose, and

when the operation is completed but little trace is left of it. The fluid

deposited with the eggs hardens and forms a protection to them,

corresponding to the more definite capsules of the cursorial Orthoptera.

The details of the process of oviposition and of the escape of the young

from their imprisonment are of much interest. According to Künckel

d'Herculais[223] the young _Stauronotus maroccanus_ escapes from the

capsule by putting into action an ampulla formed by the membrane between

the head and the thorax; this ampulla is supposed to be dilated by fluid

from the body cavity, and is maintained in the swollen condition by the

Insect accumulating air in the crop beneath it. In order to dislodge the

lid of the capsule, six or seven of the young ones inside combine their

efforts to push it off by means of their ampullae. The ampulla

{291}subsequently serves as a sort of reservoir, by the aid of which the

Insect can diminish other parts of the body, and after emergence from the

capsule, penetrate cracks in the earth so as to reach the surface.

Immediately after doing this the young _Stauronotus_ moults, the skin it

casts being called by Künckel an amnios. The cervical ampulla reappears at

subsequent moults, and enables the Insect to burst its skin and emerge from

it.

The process is apparently different in _Caloptenus spretus_, which,

according to Riley, ruptures the egg-shell and works its way out by the

action of the spines at the apex of the tibiae. This latter Insect when it

emerges moults a pellicle, which Riley considers to be part of the

embryonic membranes.

Riley states that a female of _Caloptenus spretus_ makes several

egg-masses. Its period of ovipositing extends over about 62 days, the

number of egg-masses being four and the total number of eggs deposited

about 100. The French naturalists have recently observed a similar fact in

Algeria, and have ascertained that one of the migratory

locusts—_Schistocerca peregrina_—may make a deposit of eggs at more than

one of the places it may alight on during its migration.

It has been ascertained that the eggs of Acridiidae are very nutritious and

afford sustenance to a number of Insects, some of which indeed appear to

find in them their sole means of subsistence. Beetles of the family

Cantharidae frequent the localities where the eggs are laid and deposit

their eggs in the egg-masses of the Orthoptera, which may thus be entirely

devoured. Two-winged flies of the family Bombyliidae also avail themselves

of these eggs for food, and a mite is said to be very destructive to them

in North America. Besides being thus destroyed in enormous quantities by

Insects, they are eaten by various birds and by some mammals.

Most of the Insects called locusts in popular language are members of the

family Acridiidae, of which there are in different parts of the world very

many species, probably 2000 being already known. To only a few of these can

the term Locust be correctly applied. A locust is a species of grasshopper

that occasionally increases greatly in number, and that moves about in

swarms to seek fresh food. There are many Orthoptera that occasionally

greatly increase in numbers, and that then extend their usual area more or

less; and some Acridiidae multiply {292}locally to a great extent—very

often for one or two seasons only,—and are then called locusts. The true

migratory locusts are species that have gregarious habits strongly

developed, and that move over considerable distances in swarms. Of these

there are but few species, although we hear of their swarms in many parts

of the world.

The migratory locusts do much more damage than the endemic species. In

countries that are liable to their visitations they have a great influence

on the prosperity of the inhabitants, for they appear suddenly on a spot in

huge swarms, which, in the space of a few hours, clear off all the

vegetable food that can be eaten, leaving no green thing for beast or man.

It is difficult for those who have not witnessed a serious invasion to

realise the magnitude of the event. Large swarms consist of an almost

incalculable number of individuals. A writer in _Nature_[224] states that a

flight of locusts that passed over the Red Sea in November 1889 was 2000

square miles in extent, and he estimated its weight at 42,850 millions of

tons, each locust weighing 1/16 of an ounce. A second similar, perhaps even

larger, flight was seen passing in the same direction the next day. That

such an estimate may be no exaggeration is rendered probable by other

testimony. From official accounts of locusts in Cyprus we find that in

1881,[225] up to the end of October, 1,600,000,000 egg-cases had been that

season collected and destroyed, each case containing a considerable number

of eggs. By the end of the season the weight of the eggs collected and made

away with amounted to over 1300 tons, and, notwithstanding this, no less

than 5,076,000,000 egg-cases were, it is believed, deposited in the island

in 1883.

When we realise the enormous number of individuals of which a large swarm

of locusts may consist we can see that famine is only a too probable

sequence, and that pestilence may follow—as it often has done—from the

decomposition of the bodies of the dead Insects. This latter result is said

to have occurred on some occasions from locusts flying in a mass into the

sea, and their dead bodies being afterwards washed ashore.

Locust swarms do not visit the districts that are subject to their

invasions every year, but, as a rule, only after intervals of a

considerable number of years. It has been satisfactorily {293}ascertained

that in both Algeria and North America large swarms occur usually only at

considerable intervals. In North America Riley thought[226] the average

period was about eleven years. In Algeria the first invasion that occurred

after the occupation of the country by the French was in 1845, the second

in 1864, the third in 1866, since which 1874 and 1891 have been years of

invasion. These breaks seem at first strange, for it would be supposed that

as locusts have great powers of increase, when once they were established

in any spot in large numbers, there would be a constant production of

superfluous individuals which would have to migrate as regularly as is the

case with swarms of bees. The irregularity seems to depend on three facts:

viz. that the increase of locusts is kept in check by parasitic Insects;

that the eggs may remain more than one year in the ground and yet hatch out

when a favourable season occurs; and that the migratory instinct is only

effective when great numbers of superfluous individuals are produced.

It is not known that the parasites have any power of remaining in abeyance

as the locust eggs may do; and the bird destroyers of the locusts may

greatly diminish in numbers during a year when the Insects are not

numerous; so that a disproportion of numbers between the locusts and their

destroyers may arise, and for a time the locusts may increase rapidly,

while the parasites are much inferior to them in numbers. If there should

come a year when very few of the locusts hatch, then the next year there

will be very few parasites, and if there should then be a large hatching of

locusts from eggs that have remained in abeyance, the parasites will not be

present in sufficient quantity to keep the destructive Insects in check;

consequently the next year the increase in number of the locusts may be so

great as to give rise to a swarm.

It is well established that locusts of the migratory species exist in

countries without giving rise to swarms, or causing any serious injuries;

thus _Pachytylus cinerascens_—perhaps the most important of the migratory

locusts—is always present in various localities in Belgium, and does not

give rise to swarms. When migration of locusts does occur it is attended by

remarkable manifestations of instinct. Although several generations may

elapse without a migration, it is believed that the locusts when {294}they

migrate do so in the direction taken by predecessors. Their movements are

to a large extent dependent on the wind, and it is said that they make

trial flights to ascertain its direction. When on the wing probably very

little muscular effort is necessary. Their bodies contain elastic air sacs

in communication with the tracheae, and at the time of flight it may be

presumed that the body is comparatively empty, food being wanting, and the

internal organs of reproduction, which occupy a large space when in

activity, yet undeveloped, hence the sacs have full room for expansion, as

explained on p. 283. Thus the Insects exert but little effort in their

aerial movements, and are, it is believed, chiefly borne by the wind.

Should this become unfavourable it is said that they alight and wait for a

change.

The most obscure point in the natural history of the migratory locusts

appears to be their disappearance from a spot they have invaded. A swarm

will alight on a locality, deposit there a number of eggs, and then move

on. But after a lapse of a season or two there will be few or none of the

species present in the spot invaded. This appears to be partly due to the

young locusts dying for want of food after hatching; but in other cases

they again migrate after growth to the land of their ancestors. The latter

fact is most remarkable, but it has been ascertained by the U.S.

Entomological Commission that these return swarms do occur.

[Illustration: FIG. 176.—Portions of body of _Caloptenus spretus_ to show

some of the air-sacs. (Modified from Packard.) A, Dorsal aspect of anterior

parts; B, lateral aspect of posterior parts of body; _a_, enlargements of

tracheae in head; _b_, pair of large sacs in thorax; _c_, sacs on the

tracheal trunks of abdomen; _s_, spiracles.]

In South Africa it would appear that the movements of the migratory locusts

are frequently made before the Insects have acquired their wings. Mrs.

Barber, in an account of "Locusts and Locust-Birds in South Africa,"[227]

has illustrated many points in the {295}Natural History of these Insects.

The South African species manifests the gregarious and migratory

disposition when the individuals are quite young, so that they travel in

flocks on foot, and are called by the Dutch "Voetgangers." After hatching,

the various families of young amalgamate, so that enormous numbers come

together. Having denuded the neighbourhood of all its food-supplies, they

move off in search of fresh crops and pastures new. They take advantage of

roads, and sometimes a good many miles will be traversed in a day; they

proceed by means of short leaps, rapidly repeated. When the "Voetgangers"

are thus returning northwards towards the lands in the interior from which

their progenitors departed, no obstacles can stay their course. Forests or

rivers may intervene, diverting them for a while from their line of march,

but they succeed ultimately in continuing their journey to the interior.

The manner in which these wingless locusts occasionally cross broad rivers

is interesting, as it has some bearing on the difficult question of the

possibility of winged locusts crossing seas of considerable width. Mrs.

Barber refers to an instance that took place on the Vaal River in the

spring of the year 1871, shortly after the discovery of the Diamond-fields.

The country was at that time swarming with young locusts; every blade of

grass was cleared off by them. One day a vast swarm of the "Voetgangers"

made their appearance on the banks of the Vaal River; they appeared to be

in search of a spot for crossing, which they could not find, the river

being somewhat swollen. For several days the locusts travelled up the

stream; in the course of doing this they paused for some time at an abrupt

bend in the river where a number of rocks were cropping out, as if in doubt

whether to attempt a passage at this place. They, however, passed on, as if

with the hope of finding a better ford; in this apparently they were

disappointed, for three days afterwards they returned to the same bend of

the river, and there plunged in vast multitudes into the stream, where,

assisted by a favourable current and the sedges and water-plants which grew

upon the projecting rocks, they managed to effect a crossing, though great

numbers were drowned and carried away by the flooded river. Mrs. Barber

adds that "Voetgangers" have been known to attempt the passage of the

Orange River when it was several hundred yards in breadth, pouring their

vast swarms into the flooded stream regardless of the consequences, until

they {296}became heaped upon each other in large bodies. As the living mass

in the water accumulated, some portions of it were swept away by the strong

current from the bank to which they were clinging, and as the living

locusts tightly grasped each other and held together, they became floating

islands, the individuals continually hopping and creeping over each other

as they drifted away. Whether any of the locust-islands succeeded in

reaching the opposite bank is unknown; probably some of them were drifted

on land again. They are by no means rapid swimmers; they do not perish

easily in the water when in masses, their habit of continually changing

places and hopping and creeping round and round upon each other being very

advantageous as a means of preservation. It is a common practice for the

young locusts to form a bridge over a moderately broad stream by plunging

indiscriminately into it and holding on to each other, grappling like

drowning men at sticks or straws, or, in fact, anything that comes within

their reach, and that will assist in floating them; meanwhile those from

behind are eagerly pushing forward over the bodies of those that are

already in the stream and hurrying on to the front, until at length by this

process they reach the opposite bank of the river; thus a floating mass of

living locusts is stretched across the stream, forming a bridge over which

the whole swarm passes. In this manner few, comparatively speaking, are

drowned, because the same individuals do not remain in the water during the

whole of the time occupied by the swarm in crossing, the Insects

continually changing places with each other; those that are beneath are

endeavouring to reach the surface by climbing over others, whilst those

above them are, in their turn, being forced below. Locusts are exceedingly

tenacious of life, remaining under water for a considerable time without

injury. An apparently drowned locust will revive beneath the warm rays of

the sun, if by chance it reaches the bank or is cast on shore. Mrs. Barber

relates an interesting case where the instinct of the "Voetgangers" was at

fault, they plunging into a river from a steep sandy bank, only to find

another similar sandy precipice on the other side. On this they could gain

no footing, and all perished in the stream, where they putrefied, and

caused the death of the fish, which floated likewise on the surface; so

powerful were the effluvia produced that no one was able to approach the

river.

{297}Locusts are able to travel considerable distances, though how far is

quite uncertain. Accounts vary as to their moving by night. It has,

however, been recently proved that they do travel at night, but it is not

ascertained how long they can remain in the air without descending. The

ocean is undoubtedly a source of destruction to many swarms; nevertheless,

they traverse seas of considerable width. They have been known to reach the

Balearic Islands, and Scudder gives[228] a well-authenticated case of the

occurrence of a swarm at sea. On the 2nd of November 1865 a ship on the

voyage from Bordeaux to Boston, when 1200 miles from the nearest land, was

invaded by a swarm of locusts, the air and the sails of the ship being

filled with them for two days. The species proved to be _Acridium_

(_Schistocerca_) _peregrinum_. This is an extraordinary case, for locusts

do not fly with rapidity, being, indeed, as we have remarked, chiefly

carried by the wind. Possibly some species may occasionally rest on the

water at night, proceeding somewhat after the fashion of the "Voetgangers"

when passing over rivers as described by Mrs. Barber. In Sir Hans Sloane's

history of Jamaica an account of an occurrence of this kind is given on the

authority of Colonel Needham, who states that in 1649 locusts devastated

the island of Tenerife, that they were seen to come from Africa when the

wind was blowing thence, that they flew as far as they could, then alighted

on the water, one on the other, till they made a heap as big as the

greatest ship, and that the next day, being refreshed by the sun, they took

flight again and landed in clouds at Tenerife. De Saussure says[229] that

the great oceans are, as a rule, impassable barriers, and that not a

species of the tribe Oedipodides has passed from the Old World to the New.

It is, however, possible that _Acridium peregrinum_, of the tribe

Acridiides, may have originally been an inhabitant of America, and have

passed from thence to the Old World.

{298}[Illustration: FIG. 177.—European migratory locust, _Pachytylus

cinerascens_ ♀.]

The species of Acridiidae that have been ascertained to be migratory are

not numerous.[230] The most abundant and widely distributed of them is

_Pachytylus cinerascens_ (Fig. 177), which has invaded a large part of the

Eastern hemisphere, extending from the Atlantic Ocean to China. It exists

in numerous spots in the Oriental region and the Asiatic Archipelago, and

even in New Zealand. It is the commoner of the locusts of Europe. Its

congener, _P. migratorius_, is much less widely distributed, its migrations

being, according to de Saussure, limited to Turkestan and Eastern Europe. A

third species, _P. migratorioides_, inhabits Eastern Africa, and a variety

of it is the "Yolala" or locust of Madagascar. Mr. Distant has informed the

writer that this migratory locust is found in South Africa. _P._

(_Oedaleus_) _marmoratus_ has almost as wide a distribution in the Eastern

hemisphere as _P. cinerascens_, except that it is more exclusively

tropical; it is thus excluded from New Zealand. _P._ (_Oedaleus_)

_nigrofasciatus_ has a more northern distribution than its congener, but

has extended to Africa and the Asiatic Archipelago. This Insect is so

variable that the distinctions of its races from other species of the same

genus are not yet clear. All the above-mentioned locusts belong to the

tribe Oedipodides. _Acridium peregrinum_, now more frequently called

_Schistocerca peregrina_, belongs to the tribe Acridiides. It is a large

locust (Fig. 84), and has a wide distribution. It is the chief species in

North Africa, and is probably the locust of the plagues of Egypt mentioned

in the book of Exodus. It is also, according to Cotes,[231] the chief

locust of North-West India. In this latter country _Pachytylus cinerascens_

and some other species also occur. With the exception of _S. peregrina_,

the species of the genus _Schistocerca_ are confined to the New World. In

North America locusts are more usually called grasshoppers. Several species

of the genus _Caloptenus_ are injurious in that country, but the chief

migratory species is _C. spretus_ (Fig. 175). This genus belongs to

Acridiides. A large locust, _Schistocerca americana_, is also migratory to

a small extent in the United States. In South America other species of

_Schistocerca_ are migratory; it is not known how many there may be, and it

is possible that one or more may prove to be the _S. peregrina_ of the Old

World. A Chilian species, according to Mr. E. C. Reed,[232] {299}exhibits

distinctions of colour similar to those that have been observed in _S.

peregrina_ in Algeria.

[Illustration: FIG. 178.—_Cephalocoema lineata_, female, × ⅔. S. America.

(After Brunner.)]

In Britain we are now exempt from the ravages of locusts, though swarms are

said to have visited England in 1693 and 1748. Individuals of the migratory

species are, however, still occasionally met with in England and the south

of Scotland. _P. cinerascens_ has been recorded from Kerry in Ireland, but

erroneously, the Insect found being _Mecostethus grossus_ (Fig. 173).

According to Miss Ormerod,[233] large locusts are imported to this country

in fodder in considerable numbers, but are usually dead; living individuals

are, however, sometimes found among the others. In 1869 living specimens of

_Schistocerca peregrina_ were found in various parts of the country,

having, in all probability, arrived here by crossing the German Ocean.

_Pachytylus cinerascens_ has also, it is believed, occurred here, the

specimens that have been recorded at different times under the name of _P.

migratorius_ being more probably the former species.

Although the majority of the very large number of species included in

Acridiidae are recognised with ease from their family likeness as belonging

to the group, yet there are others that present an unusual aspect. This is

specially the case with the members of the small tribes Tettigides,

Proscopides, and Pneumorides, and with some of the apterous forms of the

Oedipodides. The tribe Proscopides (Fig. 178, _Cephalocoema lineata_,

female) includes some of the most curious of the Acridiidae. Breitenbach

gives[234] a brief account of the habits of certain species which he met

with near Porto Alegre in South America. On a stony hill there was some

grass which, by several months' exposure to the sun's rays, had {300}become

withered and brown. Apparently no live thing was to seen on this hillock

except the ubiquitous ants, but after a while he noticed some

"lightning-like" movements, which he found were due to specimens of

Proscopia. The Insects exactly resemble the withered vegetation amongst

which they sit, and when alarmed seek safety with a lengthy and most rapid

leap. When attention was thus directed to them he found the Insects were

really abundant, and was often able to secure fifty specimens on a single

afternoon. These Insects bear a great general resemblance to the Phasmides,

but there is no evidence at present to show that the two kinds of Insects

live in company, as is the case with so many of the Insects that resemble

one another in appearance. Although the linear form and the elongation of

the body are common to the stick-Insects and the Proscopides, yet this

structure is due to the growth of different parts in the two families. In

the Phasmidae the prothorax is small, the mesothorax elongate, while in the

Proscopides the reverse is the case. The elongation of the head is very

curious in these Insects; the mouth is not thus brought any nearer to the

front, but is placed on the under side of the head, quite close to the

thorax. The tribe Tryxalides contains Insects (Fig. 165) that approach the

Proscopides in the form of the head and other characters. In most cases the

sexes of the Proscopides differ from one another so strongly that it is

difficult to recognise them as being of the same species. Usually both

sexes are entirely apterous, but the Chilian genus _Astroma_ exhibits a

remarkable exception and an almost unique condition of the alar organs, the

mesonotum being in each sex entirely destitute of such appendages, while

the female has on the metanotum rudiments of wings which are absent in the

male.