True Tales of the Insects

nowhere in circumference except at the base of the legs. Some species of Bacteria are so excessively slender that the linear body is scarcely as thick as one of the legs it bears. Others, again, can fly, having ample wings, and, oddly enough, often gayly coloured. Look at the large spectre Aa^op/iylla titmi of Australia, a giant of its kind (see Fig. 14): its charming wings generally blackish brown in colour, but irregularly spotted and banded with white, the costal portion variegated with green and pink, and expand fully eight inches; while the long cylindrical body itself exceeds this length, and is as thick as a man's little finger. Some kinds of Tropidoderus and Podacanthus, also from Australia, likewise expand eight and even nine inches in flight, and have a stouter though shorter cylindrical body. Podacanthus typ/ion, the pink-winged spectre, is one of the showiest species, owing to its size and the fine pink colour which tinges the hyaline wings; while the front portion of the wings, like the short tegmina, is of a grass-green: but when at rest the immense and brilliant wings fold up jike a fan, so that the pink colour is completely concealed under the narrow front and wing-covers, and the whole stick-like insect is then crreen or brown, and almost invisible amon^ the twisfs or foliao^e.

!

Bizarre Shapes Galore.

Almost all the foregoing forms are smooth-bodied, or have merely little insignificant inequalities of skin. But to increase the resemblance to vegetation, some of these Phasmas have the oddest unequal surfaces imaginable, so that they resemble the roughened bark of the trees among which they live, or bits of rotten wood, or lichen-covered bark. There are bizarre appearances among them which defy description. They have growing to them or sprouting from them almost everywhere, more especially from the abdomen and legs, delicate small green processes or foliaceous excrescences, looking exactly like the Hepatica^, or moss. They inhabit damp forests both in the Malay Isles and America, and it needs careful scrutiny to detect that the apparent piece of rotten moss-grown twig is in reality a living insect. See Ceroys laciniatus (Fig. 16) from Nicaragua; how these irregular leaf-like expansions protrude all over it Could one wish for anything more grotesque than the bulky, prickly, spiny, briefly-winged giant Heteropteryx, from India, Borneo, Sumatra, and Australia, or than a Peruvian Ceroys, typifying thorny stems } Or, turn to the dilated-bodied spectre Extatosoma, hailing from Australia, from Tasmania, and New Guinea, enormously thick as compared with the males, and with both the

wings and the wing-covers rudimental, like tiny sprouts. The body is spinous, furnished with membranous lobes or dilations at the side; it is spined on the thorax, the abdomen is spined, so are the dilations of the legs, and the peculiar small pyramidal head is strongly spinous at the apex.

End gained by this Mimicry.

This armature, these details of form and colouring, may in all cases be regarded as developed for protective purposes. Protection in resemblance, and thus concealment, is a very general and very effectual means oi maintainin^r life "in the ceaseless struQfMe for existence. Walking-sticks being perfectly inoffensive and herbivorous, and therefore needing no special qualification for facilitating capture of prey, their mimicry is purely defensive, its ultimate end to elude their enemies. Obviously, their harmlessness, their solitary instinct, their sluggish motions, as a rule, and incapacity for what can be properly called flight, their soft and succulent nature, so that they are eagerly devoured, render them particularly open to attack. Their defence, their very existence, depends upon their being by form and colour concealed from enemies. That their vegetable disguises deceive their natural enemies the numbers

that escape destruction prove: without them, they must soon be exterminated. There is no family to which this protection is more indispensable, and in none, perhaps, is it so generally and so perfectly possessed. Given a walking-stick hugging the stem of a bush or a leaf, with its two hinder pairs of legs stretched straight alongside the body, the front pair outstretched in the opposite direction, and the antennce snugly tucked between them, the deception immeasurably increased in efficacy by its immobility, it must be a sharp-sighted creature to ever discover its presence. Even those provided with the most splendid and expansive wings use them rarely, and that -use, as we have seen, is of the briefest description. Whenever they settle the great wings close; their beauties are no longer displayed. An insectivorous foe spying such a walking-stick in flight, and making for it, would search in vain for what he had seen; the gorgeous aerial being alighting, had suddenly transformed itself into its more habitual unobservable stick shape.

Leaf-Insects.

All these Phasmidce are noted for their lank and usually slender bodies and legs. But there is an exceptional form of walking-stick. These have remarkably

expanded bodies; they are known a.s Walking-Leaves, from the striking resemblance they present to the leaves of trees. While seated among the leaves of the trees on which they live, no more exact representation of a growing leaf could be conceived. Not one person in ten can see a leaf-insect when resting on the food plant close beneath their eyes. It is principally the tegmina or front wings that display this great resemblance in Orthoptera, and in none of the order is the extraordinary phenomenon more marked than it is in these Walking- Leaves, of the genus Phyllium. The genus constitutes by itself the tribe Phylliides, the members of which

Fig. 1 6. Ceroys Icuiniatus, from Nicaragua: irregular belong exclusively to the tropics leaf-like expansions pro- of the Old World, coming from trude all over it. the Philippine Isles, Java, and Ceylon; in fact, they extend from Mauritius and the Seychelles even as far east as the Fiji Isles, having, it would appear, a strange penchant for insular life. Although the group has been very inadequately in-vestigated, some twenty species are known, and the

individuals are believed to be not uncommon, notwithstanding- the limited number of specimens that our collections contain. As will be seen from Figr. 18, the resemblance to a leaf of the tegmina is of the most remarkable nature, and the other details must add greatly to the deceptive appearance in their native haunts. The imitation of a leaf is carried out with a deo-ree of exactitude so surprising, that it seems, in truth, that the whole insect has been shaped and charged with appendages to produce the perfect resemblance. The body, which escapes completely from the family type, has become large, oval, and depressed; the antennae have become extremely short, and are flattened; all the legs compressed and dilated in leaflet form; the hind wings atrophied, being represented merely by a minute process; while to the broad leaf-like tegmina lying flat on the back, the head and small prothorax together form, as it were, the swollen petiole or leaf-stalk, on both sides of which the flat leaf-like expansions on the front legs answer admirably as stipules. The insects feed only at night, resting motionless during the day, aiding them to elude detection. During the early stages, when the insect does not possess the tegmina, it is said then to adapt itself to the appearance of leaves, by the movements it makes, and the positions it assumes augment the resemblance.

In these wonderful Eastern leaf-insects of the genus Phyllium, it is the female only that so marvellously imitates a green leaf; she alone is possessed of the large leaf-like tegmina. The males of the genus are altogether different from the females; having instead of the foliaceous teo-mina, short wingf-covers that are not leaflike, while the gauzy hind wings, which are particularly large and conspicuous, are totally devoid of leaf-like appearance.

Tegmen of the Female an Exceptional Stntctnre.

This disguise of the female in respect of its tegmina is striking to a naturalist from various points of view. He will notice that whereas when there is in insects a difference between the organs of flight of the two sexes, the male has them largest, the very opposite is true of Phyllium; that is to say, the normal condition is adhered to so far as the hind wings are concerned, but in the front pair the rule is reversed, the leaf-like tegmina of the female exceeding greatly the rudimentary wing-covers of the male. He will also observe as one of the peculiar traits of the family, a trait shown by all other members of the tribe, that the wing-covers or tegmina (when they exist) are greatly abbreviated, even when the wings are largely developed. This is the case in

the male of Phyllium, but the female offers precisely the opposite the wing-covers, the only character-members susceptible of such exact mimicry of a leaf, being greatly developed, while the wings are aborted. There is this to be pointed out, that had the wings, and not the tegmina, been made to resemble a leaf, the mesothorax would have remained entirely visible; it would have spoilt the perfection of the resemblance of the insect and a leaf, by forming with the head and prothorax a petiole, as it were, too large, and too apparent. Nature has then, contrary to the general rule, atrophied the wings and developed the tegmina, to obtain the appearance of a leaf over the largest surface of the body possible. The great reduction of size of the prothorax and antennee, parts which would equally interfere with the resemblance, is likewise to be included in this artifice, tending to the same end.

Another surprising it is probable that the thing-female tegmen of Phyllium is a structure as peculiar morphologically as it is in other respects. In order the better to imitate a leaf, the radial vein is placed quite close to the posterior edge, permitting the radial veins of the tegmina, when they come together, to juxtapose, typifying the principal nerve or mid-rib of a leaf. The lateral ribs of the leaf are represented exactly by the oblique costal veins. It will thus be plain, that the tegmina of female Phyllium not only break a rule

that is almost universal in the Insecta, and reverse the normal condition in the family to which they belong; but also differ widely from the same parts of its mate, in quite anand, moreover, are completely different-its own otherexceptional manner for a Phasmid—from pair of organs of flight. This extreme resemblance of Phyllium to a leaf has attracted the notice even of the natives of the tropics where they abound, where little or nothing is known of natural history. In many such places, as in the Indies, it has given rise to the singular belief that the insects are truly transformed leaves, by which the inhabitants understand a bud developing into a leaf, and subsequently being converted into a walking-leaf insect. We have evidence of the idea obtaining credence in Ceylon, and no explanation could shake the rooted conviction in the reality of this miracle. When first brought into notice in this country they created unbounded surprise. Thus Richard Bradley, a fellow of the Royal Society, and at one time Professor of Botany in the University of Cambridge, writes of them iri 1739' in a philosophical work, in a fashion fully as grotesque as any legend of the countries which they inhabit. This fanciful author regards them as exhibiting identity of animal and vegetable development, "being nourish'd," he observes, "as well by the Juices of the Tree, which the Mother Insect lays its eggs in, as by its