Chapter XV: Introduction: Habits–classification–structure–chilognatha–chilopoda (9)

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.

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.

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.

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:—

"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.

{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_.

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}

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.

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.

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.

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.

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.

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.

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.

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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).

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.

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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.

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.

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_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.

)]

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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._

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.

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.

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