elytra, as the fore We have seen that the teomina, or wings are called, are usually of small size or absent, and when present are attached at the posterior part of the mesothorax. Most often they have the form of scales, and cover merely the base of the wings, and are coriaceous, generally raised in the form of a tubercle, and opaque. The lower, or true wings, on the other hand, may be very large, extending in repose, in a limited number of species however, as far as the extremity of the abdomen, without exceeding it, and are attached to the anterior part of the metathorax. This attainment of a greater development of the wings than the elytra is opposed to what obtains in the other families. When one of the pairs of appendages are wanting, it is on the elytra the complete atrophy falls. In the genus Aschipasma, for example, one finds the wings fully developed, but elytra none; and in Phantasis we discover vestiges of hind wings, but of elytra similarly no trace whatever. True, an exception occurs among Phyllium females, where the upper wings become developed and the lower ones dwindle away; but this is for a special purpose, which will be dealt with later on.

In the absence of wing-covers of a size adequate to protect the normal wings in repose, it is essential that provision be made for their defence. This is effected by the outer margin of the hind wing itself, which is greatly thickened, serving as a flat plate or sheath to the greater

part of the wing-. Beneath it the wing is folded longitudinally in a complicated fan- like manner, and reposes on the back; and seeing the narrow condition of the body, this coriaceous sheath-like portion must be narrow too, in order to adapt itself to the surface of the abdomen. It looks as if it were really a tegmen; moreover, this appearance is enhanced by the fact, that it is often quite differently coloured from the rest of the organ. In some species it is green, like the short wing-covers, whilst the other part of the wing is pink. Among many, however, both organs of flight exist in a more or less rudimentary state (see Fig. 1 7), and many more remain throughout their lives without ever acquiring wings or wing-covers. The antennae are very variable; and the same remark applies to the colour of the body in many Phasmidae, which may change from brown in early life, to green, subsequently returning to the brown tint. If this be owing to the presence of chlorophyll or other plant-juices among the insect-tissues, its explanation is not far to seek.

Characteristics and Habits.

Chiefly inhabitants of tropical countries, these insects are extremely sensitive to cold; the occurrence of frost puts an end to their existence. They live on vegetation,

lying close to leaves and the branches of low shrubs, and are strictly herbivorous. They devour the leaves, and especially the young glutinous or gummy shoots of the plants on which they reside, and with a voracity so excessive that a single pair will destroy a great quantity of foliage, so that in some parts of the world where they abound they become very injurious. This occurs in the South Sea Isles, in the case of Gracffca coccophag7is, a brown slender species, which sometimes commits dreadful devastation in the plantations of cocoanut trees, occa-sioning scarcity of food, and orders have been issued by the chiefs for their destruction. One writer goes so far as to ascribe the cannibalism in some of these islands to the want of food caused by the ravages of this insect. Diaplieromcra ftinorata, common over the greater part of the United States, has also on several occasions appeared in such numbers as to be seriously destructive to foliage in the forests. But taken as a whole, they are far from abundant enough to do any real harm.

Immobility; the Reason and the Use thereof.

Their large size notwithstanding, they are timid inoffensive creatures, and of sluggish mode of life, as their structure indicates. Their body is much too linear, and too long, in the majority of species, to be

adapted for rapid walking; indeed, the entire organization of the greater number is such as to impede, rather than to give play to, their means of locomotion. The legs themselves, feeble and of inordinate length, sometimes almost thread-like and very fragile, form obviously far from perfect ambulatory organs. When their owner attempts to stand upright it appears in a state of unstable equilibrium, and has a curious lateral swaying motion, much like a rope-walker, that is most ludicrous. Among the slenderest species the limbs seem to fulfil better the functions of grips or catches than of ambulatory organs, permitting of the insect getting from one branch, or from one bush to another, by enabling it to lay hold of distant supports. Motion for the apterous species, then, is slow and laborious, and they pass the greater portion of their time in a state of immobility, applied against foliage, only shifting their quarters through exigency of obtaining food. Doubtless there are forms among them belonging to the type described, and to other types, that approach more nearly to what we may call the normal form, whose bodies are less slender, their legs shorter and less attenuated, and better fitted for walking, but none the less they are sluggish insects, which live clinging to the branches and leaves of plants. Winged species (see Fig. 12), like the giant Acrophylla of Australia, which has a comparatively stout body, and

the different kinds of Tropidoderns and Podacanthus, bulkier still, and shorter, have greater facility of move-

FlG. 12.— Tropidoderns rliodonius.

ment; but the large wings are employed rather momentarily than for anything properly called flight, merely as assistance in leaping to a safer place, rather than for transport to long distances.

Defenceless, and incapable for the most part of rapid movement or of flio^ht, the Walking-Sticks have no other means of escape from their enemies than to pass undetected, in concealing their existence from other animals by their immobility. It is this immobility that renders effective the extraordinary and important characteristic their imitative resemblance tothat distinguishes them-vegetative objects. Thanks to it, they succeed in effectually deceiving the eye of the sharpest enemy. Little as it might appear, they have considerably less to fear birds as foes, by which some are much relished for food, than small animals that prowl among the bushes, particularly lizards; and among insects the Mantidai, which live in the same spots, and are armed for battle in a manner that no Phasma could resist. Several bugs, too, suck the Phasmidai. One species is known to have harboured Ichneumon-flies in its body without suffering any apparent harm from their presence or their emergence. There is perhaps no other group of insects which is so generally imitative, and w^hich naturalists have experienced greater difficulty in detecting in their haunts, a difficulty heightened by their habit of living solitary, or in pairs. Apterous individuals, such as Diapheromera, however, seem to possess gregarious tastes, often a whole colony being found clustered together, distributed over the branches of the same bush. Having succeeded in discovering one, the investigator.

to his surprise, is not long in distinguishing others, which, owing to this imitative resemblance, he may have seen for a long time, have even examined with care, without recognizing anything out of the way, mistaking the livinof insects for the dead branches.

More Means of Defence.

Putting on one side for the present this wholesale Mimicry of the Phasmidae, with its protective value, we find some, at least, of the insects in the possession of peculiarities which perhaps one ought to consider as means of defence. The prickles and spines with which the Heteropteryx, Extatosoma, and other ugly monsters are clothed must make them somewhat formidable morsels for insect-eaters to assail; and there are many which have even a more potent means of defence in the power, to a greater or less extent, of ejecting a nauseous fluid. One species is named Phasnia puHdum, from the offensive nature of the secretion discharged, A sluggish creature common in some of the United States, Anisomorpha will, if seized, emit a vapour that slightly burns one's skin; and the highly acrid fluid squirted out by Graejfea coccophagus when alarmed, causes great pain, and sometimes blindness, when it strikes the eyes: one of the South African species is said to be able to eject its fetid

fluid to a distance of five feet. This liquid comes from two glands or pores placed in the prothorax, more or less apparent according to the species. In some, as among Anisomorpha, they are of exceptional size, quite occupying the sides of the thorax.

For some of the Phasmid?e there appears to be another those remarkable species which constitutesafeguard—for the rare examples which are believed to possess aquatic habits. An odd Brazilian species, one of the Prisopi, has the peculiar habit of hiding under stones submerged in the mountain streams, being enabled so to do by the hollowed lower side of the body, and the dense fringe of hairs with which it is in various parts beset; it is supposed to expel the air from the body so as to adhere to the upper surface of a stone. A still more curious insect, probably allied to the same genus, and found in the Isle of Taviuni, seems even more profoundly modified for an aquatic life. Along the lower margins of the sides of the metathorax there stand straight out five conspicuous fringed plates, said to be a kind of branchice, or tracheal gills; these coexist with trachect opening by stigmata on the exterior of the body for aerial respiration.

WALKING-STICKS AND WALKING-LEAVES.

Ctirioiis Poiucr of reproducing Lost Limbs.

A curious and interesting thing about these creatures is their power of reproducing- lost or injured Hmbs. Limbs fraorile and so lonof look liable to be broken, especially in the insect's early stages of existence. That the accident frequently happens may be judged by the numbers of individuals one sees in collections having one of the legs disproportionately small, though perfectly formed throughout; and sometimes a specimen is met with with the two corresponding legs thus abbreviated. is, at anyExperiment shows that if during growth—that time previous to the final moult—a leg be mutilated beyond the base of the thigh, the whole leg as far as the base of the thigh is dropped before the next moult, and at this moult is renewed, either as a straight short stump, in which the articulations are already observable, or as a miniature leg; in the former case, the leg assumes at the next moult the second aspect; this latter form being always changed at the succeeding moult into a limb it neverpractically normal in every respect save in this-gains its normal size. If the injury to the leg be nearer to the body than the base of the thigh, no reproduction

is effected. Yet another interesting' feature of the walkingf-sticks the frequent extreme difference ofshould be mentioned—

the sexes. There is a general amount of resemblance between the males in being usually smaller, slenderer, and furnished with longer legs and antennae; the females being generally more robust and bulky, and with shorter limbs. Strange to say, the former often possess full-sized wings, while they are quite wanting in the other sex. When there is a difference between them as to the organs of flight, they are more fully developed in the male. On the other hand, the resemblance to portions of plants is greatest in the female sex.

Remarkable A^ahirc of the E^os.

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