True Tales of the Insects
The young, in quitting the ^g^, leaves the shell at the bottom of the cell. It already presents, in a general way, the aspect of the adult. Too feeble to use its legs, it employs a special artifice in escaping from the cell where it is confined. On the chitinous covering of the body spines are developed, directed backwards, and these
acting as a prop against the walls of the cell, the larva, by giving an unclulatory movement to the abdomen, is enabled to make its way towards the operculum with ease. There, with its back, it raises the opercular scale which closes it in, and gains its liberty to the outer world in the most natural manner.
No sooner is the flap pushed the least bit ajar than it shuts to by its own elasticity. It acts, indeed, like the spring lid of a box, so that the posterior legs and the long anal threads of the larva may be caught as in a vice; and should the spring be too strong, and the larva be unable to profit by the assistance in drawing itself from its skin, it perishes, for want of power to extricate itself. In its other sheddings the insect is no less obliged, in order to get rid of the useless tight case, to fix to some object, in default of which it has no option but to work itself out of what has become its prison, by tearing its coat with its claws. A single capsule gives birth to from fifty to a hundred larvae. These creatures, in form almost the very image of their parents, are in the beginning excessively delicate, soft, and pale, and upon issuing from their cradle they disperse, but do not venture far from its immediate vicinity. No long time is spent ere they betake themselves to hiding, among leaves and under stones, there to undergo their first moult. As yet they have not
partaken of food, nevertheless they already exhibit the suppleness of the adults, and the same poses, turning their head backwards, and holding the anterior legs folded up upon themselves, as in the actual preparatory attitude of attack. In spite of this bearing, they are singularly timid, and dart under stones at the approach of an insect. Their anterior legs still serve merely for climbing; they constantly, in fact, creep to the extremities of twigs, where they appear to repair in search of prey. During their early days their pains seem all for nought, for the sight of plant-lice, for which they are on the lookout, causes them the greatest perturbation, and it is only with extreme circumspection, and by taking as many precautionary measures as prudence can dictate, that the larvse dare to draw near, and, little by little, acquire the trick of seizing them. The young mantidai now commence to have the capability of partaking of a fairly varied insect diet. At the end of twelve or fifteen days they experience a second fatal crisis for many, for moult—a those which cannot manage to cast off the now too small envelope, die in the endeavour. By this time the mantis has advanced in its killing powers, to be able to master insects as large, for instance, as the Ephemerae. About a fortnight or three weeks later, it must again strip off its skin. In all, there are at least seven moults, but it is impossible so speak on this point with absolute certainty, owing to the difficulty of rearing these larvae in captivity.
After each moult the mantis is languid and sickly, and unequal to the chase, and relapses into the timorous state of the period of extreme youth, so that but a glimpse of an insect near by suffices to throw it into a condition of violent agitation and terror; but soon the pangs of a voracious appetite cast fear and timidity to the winds, and it freely attacks and subdues to its needs other larvae and insects. By-and-by its agility becomes such, that it not only climbs on tree-trunks with remarkable ease in pursuit of prey, and passes from branch to branch with the utmost facility, but it takes on the movements of the monkey which we meet with among adults, letting itself fall from one branch to another, hanging suspended, and recovering itself by aid of the long, sharp tibial claw.
The organs of flight appear under the form of simple prolongations of the teguments of the lateral borders of the segments of the meso- and metathorax; and in these stumps can be distinguished some of the principal parts, and they hold the normal position. The last moult suddenly develops the elytra and wings in all their extent, an enormous and truly astonishing development, one still unexplained, when we compare the voluminous organs with the little sheaths in which they were contained among the nymphs.
It is the nymphs that approach the sub-apterous adult mantidae, as among Coptopteryx females, in which the wings, although not separated from the metathorax,
exist in the state of stumps, under the form they assume during the nymph period. But whilst among mantidze, in the case of the non-separation of the organs of flight, it is always the nymph state that persists, among Phasmidce, on the contrary, the larva state is that which is preserved most often: in the last-mentioned Orthoptera, when the wings are wanting, they are entirely obliterated. The development of the mantidae, then, is arrested at a later stage, a fact indicating a more advanced step in transformation, and a nature more perfect.
o-crressive Resemblance. Protective and A
A most interesting feature of the mantidse is their presentment, in a high degree, of a phenomenon which indeed the whole order Orthoptera presents— that of adaptation to their conditions of life. In a more or less wonderful manner, their appearance harmonizes with their surroundings, with the soil or vegetation on which they live, tending to their concealment, and so escape from enemies, when the resemblance is protective; and the same circumstance is of special value in enabling them to lie in wait for, and to creep upon their prey, in which cases the resemblance is aggressive. This one of adaptation leading to concealment,character—that is of use to its possessors for two different ends,then-for defence and for attack.
Mantidae invariably imitate the colour of the spots which they inhabit, and as the greater number of species live on plants and shrubs, they have a green colour. Green is almost the normal case among mantidae. An exception to the green kinds that habitually repose upon vegetation is comprised by those which, imitating dead leaves, take a brown colour.
But there is another exception to this rule of colour among the plant-types. Sometimes Mantis religiosa is grey. This deviation may be probably regarded as due merely to the influence of the sun in arid places, where vegetation is itself parched and scanty; but it appears to become hereditary in the spots where it is oftenest produced, and where foliage is well-nigh wanting. In sandy
Fig. 8.—A ground Mantis {Enyniaphila typhon), from Egypt.
and rocky desert districts it occurs, and thus a race is developed which, in assimilating itself with the general artistic effects or colour of its environment, passes
unobserved, without attracting the fatal attention of enemies. Not only this, but in such districts the individuals of the green colour, being most conspicuous, will
Fig. 9. CJuvradodis rJioinbicollis, with prothoracic expansion and leaf-like elytra.
be readily devoured; and generation after generation the grey form will tend to repeat itself, to the gradual exclusion of the other; so also the grey form will disappear in verdant regions, where the green specimens will be
"28 TRUE TALES OF THE INSECTS.
better protected, and will propagate their kind. In this way, certain species tend to divide into two varieties, the one of a green colour appertaining to vegetation, the other grey, living amid sands and rocks.
There are species which live exclusively on sterile rocks and plains, where the alteration of colour has become an accomplished fact; they have always a grey or yellow tint, in conformity with that of the soil on which they reside. Those insects which assume colours other than green may be looked upon as a younger form, replacing an older type. They belong almost entirely to the Old World; the species of the New World appertain essentially to the class of green mantida;.
Those Ciirioits Ci'catitrcs tke Ei'cmiaphila:.
As an example of the ground-types, take those curious creatures (Eremiaphila, see Fig. 8) first discovered by Savigny at the time of the 1798 expedition to Egypt. Not by their colour alone, but by the rugosity of their body, these insects imitate the earth. They are essentially dwellers in deserts; they inhabit deserts deprived of all vegetation, and enjoy power of adaptation to their surroundings such that they always offer the most perfect identity with the shade of the sands and pebbles on which they move, giving rise to local varieties. Lefebvre, who
described them much later than Savigny, mentions that he was unable to discover any insect capable of nourishing these carnivora, and they disappeared at the borders of oases, as soon as vegetation commenced; they were confined to the absolutely arid sands where they were met. However, species have since been found in spots that support a few sorry plants. The genus Eremiaphila seems localized in the Mediterranean regions of Africa and Asia, appearing in Egypt, the desert of Luxor, the oasis, isthmus of Suez, in Abyssinia, Nubia, Algeria, and Arabia. As to the general modifications of form, one may say of the ground mantidaj, and among the Eremiaphilce in particular, the body tends to become clumsy and squat, with the anterior legs short and large, and the organs of flight atrophied. The plant-types, on the contrary, tend to lengthen: those with a slender neck and large abdomen live on leaves; the stick- like body of others renders them in keeping with nothing so much as with slender herbaceous or woody stems; their wings tend to abbreviate, and even become unfit for purposes of flight in the case of the larger species of this form, as Thespis; small kinds of the type have wings well developed.
Beautiful Examples of Special Resemblance.
It is the tropical plant-types that present in a wonderfully perfect degree the phenomenon of Protective and Aggressive resemblance, not by colour merely, repro-ducinof the ireneral effect of the surroundinofs; the resemblance may be strikingly special, in which the appearance of some particular vegetative object is more or less exactly copied in colour, and also in outline and shape. Certain mantidcc have the veining of their wings modified so as precisely to imitate that of a leaf. The body in mantidse, no less than that in walking-sticks, is subject to carry appendages, giving rise to most bizarre forms, which imitate parts of plants. But the resemblance is not produced by the same contrivances as among Phasmidae. Here it is in general the prothorax that dihites in the form of a leaf [Cheeradodis, Epaphro-dita); or the elytra have a cut-out outline {Deroplatys), or expand beyond measure {Stagmatoptera, Cardioptera), producing a marvellous resemblance to great leaves with their nervures. It is hardly possible to conceive vegetable appearances more grotesque than those brought about by the development of a number of foliaceous lobes with which the legs, the body, and head are adorned [Gongyliis); or when the insects even associate certain postures with their appendages, so as to resemble follicular fruits, or packets of leaflets (^Acanthops).