Chapter XVII: Introduction: Habits–classification–structure–chilognatha–chilopoda (11)

The geographical distribution of the Eremobiens corresponds with that of the Pamphagides, with two important differences, viz. that in the Old World the former group occupies a somewhat {308}more restricted area, and that it is represented in the New World by two peculiar North American genera, _Haldmanella_ and _Brachystola_. _B. magna_ is an Insect nearly equal in size to _Methone anderssoni_. Its peculiar form and movements have procured for it in Texas and Colorado the popular names of "buffalo hopper" and "lubber grasshopper." This Insect has not—like _Methone_—the colours of the desert sands; it is of a green tint, with comparatively smooth body, and during the day rests concealed under tufts of grass. It has apparently no sound organs, though de Saussure thinks there are structures present that are vestiges or rudiments thereof.

The family Acridiidae includes a large part of the species that make up our meagre list of British Orthoptera. Indeed, the only native Orthoptera at the present time sufficiently common to attract general attention are, in addition to the earwig, the species of the genera _Stenobothrus_ and _Gomphocerus_, whose musical instruments we have described previously. We have eight species of these Insects. They are the little grasshoppers, so common in our fields and gardens, the hunting of which is a source of much amusement to children. The Insect goes off with a sudden and long hop just as it is going to be seized, and this is appreciated by the child as very clever. The hunt, as a rule, does not result in much damage to the grasshoppers, the ingenious escape being the greater part of the pleasure. These _Stenobothri_ are remarkable for their variation in colour, and it is thought by some that they frequent spots where they find themselves a match with their surroundings. There is, however, little or no information of importance on this point extant. _Mecostethus grossus_ (Fig. 173), though larger, is very like the common field grasshoppers, but appears to have become rare since the fens were drained. The two curious little grasshoppers of the genus _Tettix_ (Fig. 179) are not uncommon. In addition to these Acridiidae, three species of migratory locusts are occasionally met with in Britain, viz. _Pachytylus cinerascens_ (Fig. 177), _P. migratorius_, and _Schistocerca peregrina_ (Fig. 84); this latter we have already alluded to as being probably the locust mentioned in the book of Exodus.

Acridiidae have never been found in amber, owing possibly to their large size and strength. There are but few fossil forms known, and these do not extend farther back in time than the Mesozoic {309}epoch. Several forms, including three peculiar genera, have been found in the Tertiary strata at Florissant. The remains from the Mesozoic layers are apparently very fragmentary and obscure.

Brongniart has instituted a family of Insects under the name Palaeacrididae[242] for some fossil Insects from the Carboniferous strata at Commentry. He considers that these Insects were abundant in the epoch of the Carboniferous strata.

The very large number of genera and species of Acridiidae have been recently arranged in nine tribes by Brunner von Wattenwyl:—

1. Feet without a claw-pad.[243] [Pronotum covering all the body.]
Tegmina lobe-like. Tribe 1. TETTIGIDES. (Figs. 179, 180, _Tettix_,
_Xerophyllum_, _Cladonotus_.)

1′. Feet with a claw-pad.

2. Antennae shorter than the anterior femora.

3. Head short, as if compressed from in front.

4. Body bladder-like, inflated.[244] [Pronotum covering half the
abdomen.] South African species. Tribe 2. PNEUMORIDES. (Fig. 182,
_Pneumora scutellaris_.)

4′. Body ordinary. Tribe 3. MASTACIDES. (Fig. 181, _Mastax
guttatus_.)

3′. Head very elongate. [Body apterous or sub-apterous.] Tribe 4.
PROSCOPIIDES. (Fig. 178, _Cephalocoema lineata_.)

2′. Antennae longer than the anterior femora.

3. Prosternum unarmed.

4. The plane of the vertex of the head meeting the plane of the
front of the head as an angle. The former produced or declivous.
The face looking down. Tribe 5. TRYXALIDES. (Fig. 165, _Tryxalis
nasuta_; Fig. 173, _Mecostethus grossus_.)

4′. Planes of the vertex and front of the head connected in a
rounded manner. Face looking forwards. Tribe 6. OEDIPODIDES.
(Fig. 177, _Pachytylus_; Fig. 185, _Methone_.)

3′. Prosternum with an elevated lamina in front, either irregularly
swollen or mucronate.

4. Foveoles of the vertex superior, contiguous, forming the apex of
the vertex. Face looking much downwards. Tribe 7. PYRGOMORPHIDES.
(Fig. 183, _Pyrgomorpha grylloides_.)

4′. Foveoles of the vertex, either superior (but not forming the
apex of the vertex), or lateral, or inferior, or quite obsolete.

{310}5. Foveoles superior, open behind. Prosternum irregularly
swollen, rarely mucronate. Tribe 8. PAMPHAGIDES. (Fig. 184,
_Xiphocera asina_.)

5′. Foveoles lateral or inferior, closed behind or (usually)
entirely obsolete. Prosternum distinctly mucronate or
tuberculate. Tribe 9. ACRIDIIDES. (Fig. 84, _Acridium
peregrinum_; Fig. 176, _Caloptenus spretus_.)

{311}CHAPTER XIII

ORTHOPTERA _CONTINUED_—LOCUSTIDAE, GREEN GRASSHOPPERS, KATYDIDS

FAM. VII. LOCUSTIDAE—GREEN GRASSHOPPERS.

_Orthoptera, with very long delicate antennae composed of many more than
thirty joints; hind legs longer than the others, thicker at the base.
Tarsi with four joints. Front tibiae usually provided with tympanal
organs placed below the knee; stridulating apparatus of males, when
present, situate on the basal part of the tegmina. Females usually with
an elongate exserted ovipositor, formed by the apposition of six pieces.
Wingless forms numerous._

An unfortunate confusion has long existed as to the term Locustidae, and has resulted in the application of the name to a group of Insects that contains none of the locusts of ordinary language. Some entomologists therefore use the term Phasgonuridea for this family, but the great majority prefer the term Locustidae.

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The Locustidae are, as a rule, more fragile Insects than the Acridiidae, from which they can be readily distinguished by the characters we have mentioned in our definition. According to Dufour, there are no air vesicles connected with the tracheal system in this family; possibly to this it may be due that none of the family undertake the long flights and migratory wanderings that have made some of the Acridiidae so notorious. Very little is known as to the life histories of the members of this extensive family of Orthoptera. Graber, however, has given some particulars as to the development of _Platycleis grisea_, and of one or two other species. He recognises five instars, but his first is probably really the second, as he did not observe the Insect in its youngest condition. Although his figures are very poor, we reproduce them, as they give some idea of the mode of growth of the wings, and of the correlative changes in the thoracic segments. It will be seen that in the first three of these instars the alar organs appear merely as prolongations of the sides of the posterior two thoracic rings, and that in D a great change has occurred in the position of these segments, so that the alar organs are free processes, the two posterior thoracic rings being insignificant in size in comparison with the now greatly developed prothorax. In E the tegmen is shown fully developed, the positions of some {313}of the rings covered by it being indicated by the letters _m_, _mt_, _ab′_. These changes are very similar to those we have described in Acridiidae, the chief difference being the greater development of the dependent wing-pads previous to the fourth instar.

The ocelli in Locustidae are much more imperfect than they are in Acridiidae, and are frequently rudimentary or nearly totally absent, or there may be but one instead of three. They are, however, present in a fairly well-developed state in some species, and this is the case with the one whose face we portray in Fig. 189, where the anterior of the three ocelli is quite conspicuous, the other two being placed one on each side of the curious frontal cone near its base. The peculiar head ornament shown in this figure exists in both sexes, and something similar occurs in a large number of Conocephalides. We have not the slightest idea of its import. Individuals of one or more species of this curious South American genus are occasionally met with alive in gardens near London. They are, no doubt, imported as eggs, for they are sometimes met with in the juvenile state, but in what way they are introduced is not known.

The ovipositor frequently attains a great length in these Insects, so as to exceed that of the body. It is used in different ways, some of the family depositing their eggs in the earth, perhaps in vegetable matter under the surface; but other species place the ova in twigs or stems of plants, arranging them in a very neat and compact manner in two series, as depicted by Riley[245] in the case of _Microcentrum retinerve_ (Fig. 190). These eggs are laid in the autumn, and in the following spring become more swollen before hatching. The Insect undergoes a moult during the process of emerging from the egg. By the time the emergence is completed the _Microcentrum_ has expanded so much {314}in size that it is a matter of astonishment how it can ever have been packed in the egg; the young commence jumping and eating leaves in a few minutes. Including the ecdysis made on leaving the egg, they cast their skins five times. The post-embryonic development occupies a period of about ten weeks. The larvae eat their cast skins. When the final moult occurs the tegmina and wings are at first quite soft and colourless, but within an hour they assume their green colour. These Insects, as remarked by Riley, make interesting pets. The people of the Amazon valley are in the habit of keeping a species in cages, and our British _Locusta viridissima_ does very well in confinement. One of the most curious habits of these Locustidae is a constant licking of the front paws. Riley says that _M. retinerve_ bestows as much attention on its long graceful antennæ as many a maiden does upon her abundant tresses, the antennæ being drawn between the jaws and smoothed by the palpi. This American naturalist also tells us that he reared three successive broods in confinement, and that the Insects gradually deteriorated, so that the eggs of the third generation failed to hatch.

The ovipositor, which is one of the most characteristic features of the Locustidae, is not present in the newly-hatched Locustid (Fig. 191, A), the organ being then represented only by two papillae placed on the penultimate segment. The structure and development of the ovipositor in _Locusta viridissima_ have been described by Dewitz.[246] Fig. 191, A, shows the young Insect taken from the egg just as it is about to emerge. The abdomen consists of ten segments, the terminal one bearing at its extremity two processes, the cerci, _a′_. These persist throughout the life of the Insect, and take no part in the formation of the ovipositor. The tenth segment subsequently divides into two (_a_, _a'′_, Fig. 191, C), giving rise to the appearance of eleven abdominal segments, and of the ovipositor springing from the antepenultimate.

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Near to one another, on the middle of the ventral aspect of the true ninth abdominal segment, are seen the two papillae (_b′_), which at first are the only visible indications of the future ovipositor. If, however, the integument be taken off and carefully examined, it will be found that there exist on the eighth abdominal plate two spots, where there is a slight thickening and prominence of the integument (Fig. 191, B, _c_). From these two spots the two lower rods of the ovipositor are produced; these two, together with the two growths from the ninth segment, form the four external rods of the ovipositor. Inside these there exist in the completed structure two other rods (Fig. 192, B, _b'′_). These are produced by a growth from the inner parts of the two papillae of the ninth segment. The relations of the six rods in their early condition are shown in Fig. 191, C, where the two primary papillae _b′_ of the ninth segment are seen with their secondary offshoots _b″_; _c′_ being the papillae of the eighth segment. The subsequent relations of the pieces are shown in Fig. 192; A exhibiting the base of the organ with the lower rods turned on one side to show the others, the shaded parts indicating {316}muscular attachments; B is a transverse section of the organ. In these figures the different parts of the appendages bear the same lettering as they do in Fig. 191. It will be seen that in the completed structures the parts _c′_ have become very intimately connected with the parts _b′_ and _b″_, which belong to another segment.

The Locustidae resemble the Acridiidae in the possession of specialised ears and sound-producing organs; neither of these is, however, situate in the same part of the body as in Acridiidae. The ears of Locustidae are placed on the front legs, below the knee; a tympanum (Fig. 193, A), or a crack giving entrance to a cavity in which the tympanum is placed (Fig. 193, B), being seen on each side of each of the anterior pair of limbs. In this family, as in the Acridiidae, three kinds of ear are recognised according to the condition of the tympanum, which is either exposed (Fig. 193, A) or closed by an overgrowth of the integument (Fig. 193, B), or in a condition to a certain extent different from either of these. The existence of ears placed on the legs is a curious fact, but it is beyond doubt in the Locustidae, and there is good reason for believing that analogous organs exist in this situation in other Insects that have special means of sound-production, such as the ants and the Termites.

The structure of these organs in the Locustidae has been investigated by Graber,[247] and their acoustic functions placed beyond doubt, though to what special kind of sounds they may be sensitive is not ascertained, this point being surrounded by even greater difficulties than those we have discussed in the case of the Acridiidae. In the Locustidae there is a special structure of a remarkable nature in connexion with the ears. In Acridiidae {317}a stigma is placed close to the ear, and supplies the internal structures of the organ with air. There are no stigmata on the legs of Insects, consequently admission of air to the acoustic apparatus in Locustidae is effected by means of a gaping orifice at the back of the prothorax, just over the base of the front leg (Fig. 101); this communicates with its fellow of the other side, and from them there extend processes along the femora into the tibiae, where they undergo dilatation, so as to form vesicular cavities, one of which is in proximity to each drum of the ear. These leg-tracheae are not connected with the ordinary tracheal system; the prothoracic stigma exists in close proximity to the acoustic orifice we have described, but is much smaller than it. It is not yet clear why the acoustic apparatus should require a supply of air apart from that which could be afforded by the ordinary tracheal system. This special arrangement—to which there is hardly a parallel in Insect anatomy—has still to be accounted for; we do not know whether the necessity for it may be connected with the respiratory system or the acoustic organ.

The chief features of the acoustic apparatus of the legs of Locustidae will be gathered from the accompanying diagrammatic transverse section through the tibia. In this figure the deep black parts indicate the outer wall of the tibia and its prolongations, the white spaces indicate the parts filled with air, while the dotted portions are occupied by blood or some of the body organs;[248] the {318}circular space _o″_ is not part of the actual structure, but represents the area of the external acoustic orifice of the prothorax; it is not, however, so large as it should be.

Although the tibial ears of Locustidae are very perfect organs, there is great difficulty in deciding on the exact nature of their functions. They would appear to be admirably adapted to determine the precise locality from which a sound proceeds, especially in those cases—and they are the highest forms—in which the tympanum is placed in a cavity the external orifice of which is a slit (Fig. 193, B); for the legs can be moved in the freest manner in every direction, so as to bring the drum into the most direct line of the vibrations. But as to what kinds of vibrations may be perceived, and the manner in which they may be transmitted to the nerves, there is but little evidence. On reference to the diagram it will be noticed that the tympanum, the tympanal vesicles, and the nervous apparatus are not in close connexion, so that even the mode by which the impulses are transmitted is obscure.

The musical organs of the Locustidae are different from those of the Acridiidae, and are invariably situate on the basal part of the tegmina. They are found, in the great majority of cases, only in the male; in the tribes Ephippigerides and Callimenides they exist in each sex. One of the wings bears a file on its inner surface, while the other—on the right side of the body—is provided with a sharp edge placed on a prominent part of its inner margin. By slightly tilting the tegmina and vibrating them rapidly, the edge passes under the file, and a musical sound is produced. These structures are limited to the small anal area of the wing, and when the tegmina are very greatly reduced in size, it is this part that still remains. There is much variety in the details of the structure. The nervures of this part of the tegmina are different in the male from what they are in the female, and, moreover, the two wing-covers of the male differ from one another. It is apparently the vibrations of the right tegmen that produce the sound, and this part usually bears a space of a glassy nature, which probably improves the character of the sound produced. Our chief British songster of this group, _Locusta viridissima_, is only provided with phonetic organs (Fig. 195) of a somewhat imperfect character, but in the genus _Mecopoda_ there is great perfection of the structures. The anal areas of the two tegmina are in this case {319}very different; that of the left one, which bears the file, being similar in texture to the rest of the wing-cover, while the corresponding part of the other tegmen is rigid and transparent, and greatly distorted, so as to create a cavity which, no doubt, improves the sound; the scraper too is very perfectly formed. The difference between this form of musical organ and that of _L. viridissima_ is curious, inasmuch as in the better instrument the important modifications are confined to one tegmen, while in the other form both tegmina are largely changed. The difference appears to be that in _Locusta_ the left tegmen, as well as the right one, acts as a sounding-board, while in _Mecopoda_ it does not do so, but when the wings are closed quite covers and conceals the musical instrument.

The Locustidae, notwithstanding the fact that their alar organs are generally more ample than those of the Acridiidae, seem to be, as a rule, of more sedentary habits, and more nocturnal in their activity. The musical powers of the different species are very varied. _Locusta viridissima_ produces a shrill and monotonous but not disagreeable, sound, and is capable of sustaining it for a quarter of an hour without any intermission, except a break for the sake of starting again immediately with greater force, like a performer on a flute. It occasionally chirps in the day, but the act is then very brief. Bates informs us that one of these singing grasshoppers, called Tananá by the natives of the Amazon valley, is much admired for its singing, and is kept in little cages. The Amazonian naturalist thought the music of this species superior to that of any other Orthopterous Insect he had heard. The name of this grasshopper is _Thliboscelus camellifolius_. It is very similar in appearance to _Cyrtophyllus crepitans_, the Insect we have represented in Fig. 187.

The most notorious of the musical Locustids are the Katydids {320}of North America. There are several species of them—they belong, indeed, to more than one genus,—but it seems that sounds somewhat resembling the words Katy-did are perceptible in most of their performances. These sounds are frequently repeated with slight variations—Katy-did, O-she-did, Katy-did-she-did. Riley describes the music of the Katydid we represent in Fig. 196 as follows:[249] "The first notes from this Katydid are heard about the middle of July, and the species is in full song by the first of August. The wing-covers are partially opened by a sudden jerk, and the notes produced by the gradual closing of the same. The song consists of a series of from twenty-five to thirty raspings, as of a stiff quill drawn across a coarse file. There are about five of these raspings or trills per second, all alike, and with equal intervals, except the last two or three, which, with the closing of the wing-covers, run into each other. The whole strongly recalls the slow turning of a child's wooden rattle, ending by a sudden jerk of the same; and this prolonged rattling, which is peculiar to the male, is invariably and instantly answered by a single sharp 'chirp' or 'tschick' from one or more females, who produce the sound by a sudden upward jerk of the wings."

Pertinacity is one of the most curious features of the performance of musical Locustids. One would say they desire to distinguish themselves as much as possible. Harris says that _Cyrtophyllus concavus_ mounts on the uppermost twigs of trees and there performs its Katy-did-she-did in rivalry with others. He says even the female in this species gives forth a feeble noise. Scudder says that some of the Katydids sing both by day and night, but their day song differs from that of the night. "On a summer's day it is curious to observe these little creatures suddenly {321}changing from the day to the night song at the mere passing of a cloud, and returning to the old note when the sky is clear. By imitating the two songs in the daytime the grasshoppers can be made to respond to either at will; at night they have but one note."

Although but little is known as to the habits of Locustidae, it is ascertained that they are less exclusively herbivorous in their food habits than the Acridiidae are; many seem to prefer a mixed diet. _Locusta viridissima_ will eat various leaves and fruits, besides small quantities of flesh. It has been recorded that a specimen in confinement mastered a humble-bee, extracted with its mandibles the honey-bag, and ate this dainty, leaving the other parts of the bee untouched. Many of the Locustidae are believed to be entirely carnivorous. Brunner considers a minority to be exclusively phytophagous. The species very rarely increase to large numbers; this, however, occurs sometimes with _Orphania denticauda_ and _Barbitistes yersini_ in Europe, and _Anabrus purpurascens_ in North America. We have already mentioned that the eggs of some species are deposited in parts of plants, and of others in the earth. The British _Meconema varium_ deposits its eggs in the galls of _Cynips_ in the autumn; these eggs do not hatch till the following spring. _Xiphidium ensiferum_ has somewhat similar habits in North America, the gall selected for the reception of the eggs being the scales formed by a species of _Cecidomyia_ on the leaves of willows. It has been ascertained that the development of the embryo in the last-named species is commenced in the autumn, but is suspended during the winter, being only completed in the following spring, eight or nine months afterwards. We owe to Wheeler[250] a memoir on the embryology of this Insect.

Some of the species have the peculiar habit of dwelling in caves. This is especially the case with the members of the tribe Stenopelmatides (Fig. 197), which frequently possess enormously long antennae and legs, and are destitute of alar organs and ears. The species with this habit, though found in the most widely separated parts of the world, have a great general resemblance, so that one would almost suppose the specimens found in the caves of Austria, in the Mammoth cave of Kentucky, and in the rock-cavities of New Zealand to be one {322}species, although they are now referred by entomologists to different genera.

The Locustidae display in the greatest possible perfection that resemblance of the tegmina to leaves which we mentioned when speaking of the general characters of the Orthoptera. The wing-covers are very leaf-like in colour and appearance in many Locustidae, but it is in the tribe Pseudophyllides and in the South American genus _Pterochroza_ (Fig. 198) that the phenomenon is most remarkable. The tegmina in the species of this genus look exactly like leaves in certain stages of ripeness or decay. In the tegmina of some of the species not only are the colours of faded leaves exactly reproduced, but spots are present like those on leaves due to cryptogamic growths. Perhaps the most remarkable feature of these resemblances is the one pointed out by Brunner von Wattenwyl,[251] viz. that the tracks and spots formed on leaves by the mining of Insects in their tissues are also represented in the leaf-like wing-covers of the _Pterochroza_; transparent spots (_a_, _a_, Fig. 198) being present, just as they are in many leaves that have been attacked by Insects. Brunner was so much impressed by these facts that he came to the conclusion that they cannot be accounted for on the grounds of mere utility, {323}and proposed the term Hypertely to express the idea that in these cases the bounds of the useful are transcended. We will mention here another peculiar case of resemblance described by Brunner as occurring in a Locustid. Two specimens of a little Phaneropterid were brought from the Soudan by the Antinori expedition, and have been described by Brunner under the name of _Myrmecophana fallax_. The Insect is said to bear an extraordinary resemblance to an ant. The most peculiar feature in the resemblance is shown in Fig. 199, A, B. The most characteristic point in the external form of an ant is the stalked abdomen, this structure being at the same time quite foreign to the Orthoptera. In the other parts of the body and in the colour generally, the _Myrmecophana_ resembles an ant, but the abdomen of the Orthopteron is not stalked; it has, however, the appearance of being so, in consequence of certain parts being of a white colour, as shown in our figure. If abstraction be made of the white parts, the form of the stalked abdomen of the ant is nicely reproduced. The specimens brought from the Soudan were wingless and destitute of ovipositor, and may be immature, but Brunner suggests that they may prove to be really mature, the ovipositor, tegmina, and wings being permanently absent. The existence of a long ovipositor would certainly detract greatly from the ant-like appearance of the Orthopteron.

It is certain that the plant-like appearance of some of the Locustidae renders them inconspicuous to the human eye in the situations they frequent. It is a matter of common observation that though the noise of their chirpings may be heard to such an extent as to make it certain that many individuals must be in the immediate neighbourhood, yet at the same time it may be most difficult to detect even a single individual. M. Boutan noticed this phenomenon in the case of _Ephippigera rugosicollis_, and tells us that the human eye can, with a little practice, acquire the art of detecting these concealed creatures. This consists {324}apparently in making use, not of a general inspection, but of a scrutiny of the outlines of the leaves and twigs of a tree. By this means, when the eye is accustomed to the task, the Insects can be detected with comparative ease; much in the same way, M. Boutan says, as a figure, placed in an engraving in such a way as to elude the eye, is appreciated with ease after the eye has once perceived it.

Some of the Locustidae are provided with means of defence of a positive nature. The Algerian _Eugaster guyoni_ ejects two jets of a caustic orange-coloured fluid from two pores situate on the sides of the mesosternum, and covered by the anterior coxae. This species is carnivorous as well as herbivorous, and produces a sound more like humming than stridulation.[252]

We have previously pointed out that some of the Acridiidae resemble the stick-Insects rather than the members of their own group; and similar cases occur amongst the Locustidae. Such a resemblance has, however, only been found in a few species of the tribe Prochilides. We figure one of these, _Phasmodes ranatriformis_, a native of South-West Australia. The very elongate linear form and the total absence of alar organs give this Insect a considerable resemblance to the stick-Insects or apterous Phasmidae. _Prochilus australis_ is allied to this curious Locustid, but the alar organs are present in both sexes, and the Insect bears a great resemblance to the winged Phasmidae. This is due not only to the general form and colour, but also to the fact that the tegmina are very narrow, which {325}causes them to look like the coloured slip on the anterior parts of the wings of some of the Phasmidae (cf. p. 266). Another case of a Locustid with elongate, slender form is found in the extraordinary _Peringueyella jocosa_ of South Africa, a member of the tribe Sagides. It has minute organs of flight, and reproduces, to a considerable extent, the form and appearance of Proscopides or of some Tryxalides.[253]

We follow Brunner in placing among the Locustidae the large Insect we represent in Fig. 201. It is remarkable on account of its tegmina and wings; these have their extremities much prolonged and curled; moreover, the flat interior area and the abruptly {326}deflexed exterior area make them look more like the wings of Gryllidae. This species has no ocelli, and is said to be destitute of ears. The inflated condition of the anterior and middle tibiae suggest that it possesses auditory structures, though there appears to be no external opening for them. This Insect is found in India, where it is said to be common on the banks of sandy rivers, living there in burrows of the depth of three feet. Very little is known, however, as to this curious Insect. It has recently been reported[254] as being injurious to tobacco and other crops on high ground in Durbungha by cutting off their roots. The local name for the Insect is _bherwa_. We should think it somewhat doubtful whether this refers really to _S. monstrosus_.

In number of species the Locustidae are perhaps scarcely inferior to the Acridiidae, and in variety of form they surpass this latter family. Many of the most gigantic forms are apterous, and these very often have a repellant aspect. The genus _Anostostoma_ is remarkable for its large head. Allied to it is _Deinacrida heteracantha_, the "Weta-punga" of the New Zealand natives, an Insect formerly abundant in the forests north of Auckland, but of late years become extremely rare. The head and body of this Insect may measure more than 2½ inches in length, and when the antennae and legs are stretched out the total length may be 14 or 15 inches. Although bulky and absolutely wingless, yet, as Buller informs us,[255] it climbs with agility, and is sometimes found on the topmost branches of lofty trees. When disturbed it produces a clicking, accompanied by a slow movement {327}of its hind legs. A second species, _D. thoracica_, lives in decayed wood, and a third, _D. megacephala_, is remarkable from the very large size of the head and mandibles in the male sex. The fact that a clicking noise is produced by the Weta-punga is of some interest, for the genus _Deinacrida_ is among the Locustidae that possess ears, but are said to be destitute of sound-producing organs.

Amongst the most remarkable of the Locustidae are the two species of which Brongniart has recently formed the genus _Eumegalodon_ and the tribe Eumegalodonidae, which is not included in Brunner's table of the tribes of Locustidae. The ovipositor is large and sabre-shaped; the male is unknown. The genus _Megalodon_ is placed by Brunner in the tribe Conocephalides; it also consists of extremely remarkable Insects.

The Locustidae appear to be of slow growth, and the autumns of Britain are usually not warm enough for them. Hence we have but nine British species, and of this number only three or four are known to occur north of the Thames. The only one that attracts attention is _Locusta viridissima_, which in some districts of the south of England occurs in considerable numbers, and attests its presence by its peculiar music. It is called the green grasshopper.

{328}The geological record is rather obscure in the matter of Locustidae. Scudder considers that a fair number of Tertiary forms are known, and says that they represent several of the existing tribes and genera. One or two have been found in Mesozoic rocks.

TABLE OF THE TRIBES OF LOCUSTIDAE

1. Tarsi more or less depressed.

2. Front tibiae furnished with auditory cavities.

3. Antennae less distant from the summit of the occiput than from the
labrum; inserted between the eyes.[256]

4. First two joints of the tarsi laterally smooth. (Posterior
tibiae furnished on each side with an apical spine.) Tribe 1.
PHANEROPTERIDES. (Fig. 196, _Microcentrum_; Fig. 199,
_Myrmecophana_. Fig. 101, _Poecilimon affinis_.)

4′. First two joints of the tarsi laterally, longitudinally
sulcate.

5. Foramina of the anterior tibiae normally open. (Fig. 193, A.)

6. Posterior tibiae furnished on each side with apical spines.

7. Prosternum unarmed. Tribe 2. MECONEMIDES.

7′. Prosternum bispinose or bituberculate. Tribe 3.
MECOPODIDES.

6′. Posterior tibiae with no apical spines. (Head prognathous.)
Tribe 4. PROCHILIDES. (Fig. 200, _Phasmodes_.)

5′. Foramina of the anterior tibiae forming a chink, or protected
by a scale. (Fig. 193, B.)

6. Anterior tibiae with no apical spines.

7. Margins of the scrobes[257] of the antennae prominent.
Tribe 5. PSEUDOPHYLLIDES. (Fig. 187, _Cyrtophyllus
crepitans_; Fig. 198, _Pterochroza ocellata_.)

7′. Margins of the scrobes of the antennae not prominent.

8. Posterior tibiae furnished above on each side with
apical spines, or with a single spine on the side.

9. Posterior tibiae either furnished with apical spines
on each side, or only on the inner side. Tribe 6.
CONOCEPHALIDES. (Fig. 189, _Copiophora cornuta_.)

9′. Posterior tibiae furnished above with an apical spine
placed only on the outer side. Tribe 7. TYMPANOPHORIDES.

8′. Posterior tibiae without apical spines. Tribe 8.
SAGIDES.

6′. Anterior tibiae furnished with an apical spine on the inner
side.[258]

{329}7. The first joint of the posterior tarsi destitute of a
free sole-lobe. Tribe 9. LOCUSTIDES.

7′. The first joint of the posterior tarsi furnished with a
free sole-lobe. Tribe 10. DECTICIDES.

3′. Antennae more distant from the summit of the occiput than from
the labrum, inserted either beneath the eyes or on their inferior
border. Tegmina and wings greatly abbreviate, scale-like; when
tegmina are present they are furnished in each sex with a tympanum.

4. Third joint of the posterior tarsi shorter than the second. Both
anterior and posterior tibiae furnished on each side with a spine.
Tribe 11. CALLIMENIDES.

4′. Third joint of posterior tarsi longer than the second joint.
Anterior tibiae with no apical spine on the inner side, and
posterior tibiae with no apical spine on the outer side.

5. Antennae inserted at the edge of the eyes. Pronotum unarmed.
Tegmina present in each sex. Anterior tibiae furnished on the
outer side with an apical spine. Posterior tibiae furnished
beneath with four apical spines. Tribe 12. EPHIPPIGERIDES.

5′. Antennae inserted distinctly below the eyes. Pronotum
spinous. Elytra in the females wanting. Anterior tibiae without
apical spine on either side. Posterior tibiae beneath with two
apical spines or with none. Tribe 13. HETRODIDES.

2′. Anterior tibiae without auditory cavities. Tegmina with no
tympanum. Tribe 14. GRYLLACRIDES. (Fig. 201, _Schizodactylus
monstrosus_.)

1′. Tarsi distinctly compressed (most of the species apterous.) Tribe 15.
STENOPELMATIDES. (Fig. 202, _Anostostoma australasiae_; Fig. 197,
_Dolichopoda palpata_.)

{330}CHAPTER XIV

ORTHOPTERA _CONTINUED_—GRYLLIDAE, CRICKETS

FAM. VIII. GRYLLIDAE—CRICKETS.

_Antennae very slender, generally long and setaceous; hind legs long,
saltatorial. Tegmina with the outer portion deflexed on to the side of
the body, and with the inner part lying flat on the body. Tarsi usually
three-jointed (rarely two- or four-jointed). Female with a long
ovipositor (except in Gryllotalpides). Apterous forms numerous._

The Gryllidae are closely connected with the Locustidae, the musical and auditory organs being in both similarly situate, and the female in both possessing, in most of the tribes, an elongate exserted ovipositor. The two families differ in the number of joints of the tarsi, in the form of the tegmina, and in the fact that in Gryllidae the portion of the wing modified for musical purposes consists of a larger portion of the organ—according to de Saussure, the discoidal as well as the anal area.

The family would be a very natural one if we were to exclude from it the mole-crickets which have fossorial front legs and no ovipositor, and the Tridactylides, which also are {331}destitute of ovipositor, and have short antennae, consisting of about ten joints.

The head is generally very large; ocelli are present, though usually imperfect; the extremity of the body bears a pair of remarkably long cerci. The hind tibiae are usually armed with very strong spines; the first joint of the hind tarsus is elongate, and terminates in two spines, between which the small second joint is often almost completely concealed; the feet are not provided beneath with pads, but only bear remote setae.

The alar organs are difficult of comprehension, and different opinions prevail as to their morphology. The tegmina are extremely different to the hind wings, and never attain large dimensions, neither do they exhibit any leaf-like or ornamental structures. In the genus _Pteroplistus_ they are formed somewhat like the elytra of Coleoptera, and close over the back of the Insect in a fashion very like that found in beetles. According to Brunner the larger part of the tegmen—which, as we have said, reposes flat on the back of the Insect—represents merely the anal area, and all the other parts must be sought in the smaller, deflexed portion of the wing-cover. De Saussure's opinion, to a somewhat different effect, we have already mentioned. The tegmina of the male are extremely different from those of the female, so that it is a matter of much difficulty to decide what nervures correspond.[259]

The wing-covers of the male differ from those of the Locustidae, inasmuch as the pair are of similar formation, each bearing a stridulating file on its lower aspect. This file projects somewhat inwards, so that its position is marked on the outer aspect of the wing-cover by a depression. Usually the right tegmen overlaps the other, an arrangement contrary to that which prevails in other Orthoptera. The wings are ample and delicate; they possess numerous nervures that are not much forked and have a {332}simple, somewhat fan-like arrangement; the little transverse nervules exhibit only slight variety. These wings are frequently rolled up at the apex, and project beyond the body like an additional pair of cerci (Fig. 204). The abdomen is chiefly remarkable for the large development of the pleura, the stigmata being consequently very conspicuous. The cerci are not jointed, though they are flexible and, often, very long; they bear a variety of sense-organs (Fig. 67). The saltatorial powers of the crickets are frequently considerable.

Graber has observed the post-embryonic development of the field-cricket, _Gryllus campestris_, though unfortunately not from the very commencement, so that we do not know whether there are five, six, or seven ecdyses; the number is probably either six or seven. The manner in which the alar organs are developed is similar to that we have described and figured in the Locustidae. In the earlier instars there is a slight prolongation of each side of the meso- and meta-notum, but about the middle of the development a considerable change occurs—the rudimentary organs then become free appendages and assume a different position.

The Gryllidae possess a pair of tympana on each front leg, but these organs contrast with those of the Locustidae in that the pair on each leg usually differ from one another, the one on the outer or posterior aspect being larger than that on the inner or front face of the leg.

The ears of the Gryllidae have not been so well investigated as those of the Locustidae, but are apparently of a much less perfect nature. No orifice for the admission of air other than that of the prothoracic stigma has been detected, except in _Gryllotalpa_. On the other hand, it is said[260] that in addition to the tibial organs another pair of tympana exists, and is seated on the second abdominal segment in a position analogous to that occupied by the ear on the first segment of Acridiidae.

The musical powers of the crickets are remarkable, and are familiar to all in Europe, as the performance of the house-cricket gives a fair idea of them. Some of the Insects of the family are able to make a very piercing noise, the note of _Brachytrypes megacephalus_ having been heard, it is said, at a distance of a mile from where it was being produced. The mode of {333}production is the same as in the Locustidae, rapid vibration of the tegmina causing the edge of one of them to act on the file of the other.

The mole-cricket, _Gryllotalpa vulgaris_—the _Werre_ of the Germans, _Courtilière_ of the French—is placed with a few allies in a special group, Gryllotalpides, characterised by the dilated front legs, which are admirably adapted for working underground. Like the mole, this Insect has a subterranean existence. It travels in burrows of its own formation, and it also forms beneath the surface a habitation for its eggs and family. Its habits have been alluded to by Gilbert White,[261] who tells us that "a gardener at a house where I was on a visit, happening to be mowing, on the 6th of May, by the side of a canal, his scythe struck too deep, pared off a large piece of turf, and laid open to view a curious scene of domestic economy: there were many caverns and winding passages leading to a kind of chamber, neatly smoothed and rounded, and about the size of a moderate snuff-box. Within this secret nursery were deposited near a hundred eggs of a dirty yellow colour, and enveloped in a tough skin, but too lately excluded to contain any rudiments of young, being full of a viscous substance. The eggs lay but shallow, and within the influence of the sun, just under a little heap of fresh moved mould like that which is raised by ants."

The front legs are remarkable structures (Fig. 206), being beautifully adapted for burrowing; the tibiae and tarsi are arranged so as to act as shears when it may be necessary to sever a root. The shear-like action of the tarsus and tibia is very remarkable; the first and second joints of the former are furnished with hard processes, which, when the tarsus is moved, pass over the edges of the tibial teeth in such a way as to be more effective than a pair of shears. In consequence of its habit of cutting roots, {334}the mole-cricket causes some damage where it is abundant. It is now a rare Insect in England, and is almost confined to the southern counties, but in the gardens of Central and Southern Europe it is very abundant. Its French name _courtilière_ is supposed to be a corruption of the Latin _curtilla_. Its fondness for the neighbourhood of water is well known. De Saussure says that in order to secure specimens it is only necessary to throw water on the paths between the flower-beds of gardens and to cover the wetted places with pieces of board; in the morning some of these Insects are almost sure to be found under the boards disporting themselves in the mud. The Gryllotalpae swim admirably by aid of their broad front legs.

Ears exist in the mole-cricket, and are situate on the front leg below the knee, as in other Gryllidae, although it seems strange that a leg so profoundly modified for digging and excavating as is that of the mole-cricket should be provided with an ear. In _Gryllotalpa_ the ear is concealed and protected by being placed in a deep slit or fold of the surface, and this depression is all that can be seen by examination of the exterior (Fig. 206, _e_). In the allied genus _Scapteriscus_ the tympanal membrane is, however, destitute of special protection, being completely exposed on the surface of the leg.

Although the tegmina or upper wings in _Gryllotalpa_ are of small size, yet the true wings are much more ample; they are of delicate texture and traversed by many nearly straight radii, so that they close up in the most complete manner, and form the two long delicate, flexible processes that in the state of repose may be seen projecting not only beyond the tegmina, but actually surpassing the extremity of the body hanging down behind it, and looking like a second pair of cerci.

The mole-cricket is believed to be chiefly carnivorous in its diet, though, like many other Orthoptera, it can accommodate its appetite to parts of the vegetable as well as of the animal kingdom. The Insect is capable of emitting a sound consisting of a dull jarring note, somewhat like that of the goat-sucker. For this purpose the tegmina of the males are provided with an apparatus of the nature we have already described, but which is very much smaller and less elaborate than it is in the true crickets.

{335}

The alimentary canal and digestive system of _Gryllotalpa_ present peculiarities worthy of notice. Salivary glands and reservoirs are present; the oesophagus is elongate, and has on one side a peculiar large pouch (Fig. 207, _c_); beyond this is the gizzard, which is embraced by two lobes of the stomach. This latter organ is, beyond the lobes, continued backwards as a neck, which subsequently becomes larger and rugose-plicate. On the neck of the stomach there is a pair of branching organs, which Dufour considered to be peculiar to the mole-cricket, and compared to a spleen or pancreas. The single tube into which the Malpighian tubules open is seated near the commencement of the small intestine. These tubules are very fine, and are about one hundred in number. The arrangement by which the Malpighian tubules open into a common duct instead of into the intestine itself appears to be characteristic of the Gryllidae, but is said to occur also in _Ephippigera_, a genus of Locustidae. According to Leydig[262] and Schindler the Malpighian tubules are of two kinds, differing in colour, and, according to Leydig, in contents and histological structure. Near the posterior extremity of the rectum there is a lobulated gland having a reservoir connected with it; this is the chief source of the foetid secretion the mole-cricket emits when seized. The nervous chain consists of three thoracic and four abdominal ganglia; these latter do not extend to the extremity of the body; {336}the three anterior of the four ganglia are but small, the terminal one being much larger.

The number of eggs deposited by a female mole-cricket is large, varying, it is said, from 200 to 400. The mother watches over them carefully, and when they are hatched, which occurs in a period of from three to four weeks after their deposition, she supplies the young with food till their first moult; after this occurs they disperse, and begin to form burrows for themselves.

It has been said that the young are devoured by their parents, and some writers have gone so far as to say that 90 per cent of the progeny are thus disposed of. M. Decaux, who has paid considerable attention to the economy of the mole-cricket,[263] acquits the mother of such an offence, but admits that the male commits it. The number of eggs in one nest is said to be about 300.

The embryonic development of the mole-cricket has been studied by Dohrn[264] and Korotneff,[265] and is considered by the former to be of great interest. The tracheae connected with each stigma remain isolated, while, according to Korotneff, the development of the alimentary canal is not completed when the young mole-cricket is hatched. Perhaps it may be this condition of the digestive organs that necessitates the unusual care the mother bestows on her young.

The genus _Cylindrodes_ (Fig. 208, _C. kochi_) comprises some curious and rare Insects of elongate, slender form. They are natives of Australia, where the first species known of the genus was found in Melville Island by Major Campbell, from whom we learn that these Insects burrow in the stems of plants, and are so destructive that he was unable to keep a single plant in his greenhouse on account of the ravages of _Cylindrodes campbellii_. The form of these Insects is beautifully adapted to {337}their habits, the body being contracted in the middle in such a way as to permit the middle and hind legs to be packed against it, so that the cylindrical form is not interfered with by these appendages while the excavating anterior legs are at work in front of the Insect. The abdomen has nine segments; the terminal one, said to be remarkably long and destitute of cerci, is not shown in our figure.

The genus _Tridactylus_ is considered by de Saussure to form, with its ally _Rhipipteryx_, a division of Gryllotalpinae, but they are treated, perhaps more correctly, by Brunner as a separate tribe. _T. variegatus_ (Fig. 209) is a small Insect, abundant in sandy places on the banks of rivers in Southern Europe,—extending on the Rhone as far north as Geneva,—and is remarkable for its great power of leaping, and for the rapidity with which it can burrow in the sand. This anomalous Insect has only ten joints to the antennae. Its alar organs are imperfect, and not like those of other Gryllidae in either form or neuration. The hind legs are of peculiar structure, the tibiae terminating in two processes between which is situate a rudimentary tarsus. Near the extremity of the tibia there are some plates, forming two series, that can be adpressed to the tibia, or extended as shown in our figure. The body is terminated by four rather short, very mobile processes; the upper pair of these are each two-jointed, and are thought by de Saussure and Haase[266] to be cerci; the inferior pair, being articulated processes of the anal segment, their presence in addition to cerci is remarkable. It is difficult to distinguish the sexes of this Insect.

The exotic genus _Rhipipteryx_ is allied to _Tridactylus_. It is widely distributed in South America, but the little Insects that {338}compose it are rare in collections, their saltatorial powers no doubt making it difficult to catch them; little is known as to their habits. In the undescribed Amazonian species we figure (Fig. 210), the wings, instead of being mere rudiments, as in _Tridactylus_, are elongate and project beyond the body; they are of a blue-black colour, and arranged so as to look as if they were the abdomen of the Insect; they, moreover, have a transverse pallid mark, giving rise to an appearance of division. It is difficult to form any surmise as to the nature of so curious a modification of the wings.

The Tridactylides have no tympana on the legs, and their affinity with the Gryllidae is very doubtful. Dufour thought _T. variegatus_ to be more allied to the Acridiidae. He based this opinion chiefly on some points of the internal anatomy, but pointed out that _Tridactylus_ differs from the Acridiidae in having no air-sacs in the body.

Not many of the Gryllidae are so peculiar as the forms we have mentioned. The family consists in larger part of Insects more or less similar to the common cricket, though exhibiting a great variety of external form. The common cricket of our houses, _Gryllus (Acheta) domesticus_ (Fig. 204), has a very wide distribution in the Old World, and is also found in North America. It is believed to have had its natural distribution extended by commerce, though really nothing is known as to its original habitat. The shrill chirping of this little Insect is frequently heard at night in houses, even in the most densely inhabited parts of great cities. Neither the female nor the young are musical, yet the chirping may be heard at all seasons of the year, as young and adults coexist independent of season. The predilection of _Gryllus domesticus_ for the habitations of man is very curious. The Insect is occasionally found out of doors in the neighbourhood of dwelling-houses in hot weather, but it does not appear that this species leads anywhere a truly wild life. It is fond of heat; though it rarely multiplies in dwelling-houses to any great extent, it is sometimes found in profusion in {339}bake-houses. Usually the wings in the cricket are elongate, and project backwards from under the tegmina like an additional pair of cerci; a variety, however, occurs in which these tails are absent, owing to abbreviation of the wings.