True Tales of the Insects
screened from the fierce rays of the sun within a thin, transparent, silky web. At night, no longer sluggish, it quits its cover, greedily stripping Omphalea of its foliage, so that trees are left with scarcely a single leaf; nor is it inactive in the daytime when disturbed, but can run about quickly, and shows little affinity to the caterpillars of other diurnal Lepidoptera, which usually have a slow motion. In February, and the ensuing months of spring and summer, the perfect insect deposits its eggs on the tender incised leaves, laying them singly, and apparently rarely attaching more than two to the same leaf, gluing it merelyeach ^g^ to its destined leaf by alighting on for a moment. They are pale green, sometimes turning to yellow, and spherical as a rule; and on the whole their surface is not smooth, but ornamental, for from the summit proceed a number of longitudinal ribs, the spaces between which are crossed at right angles by obsolete striae. The young larva, just hatched, is of nearly the same pale green, with a yellowish head, but ere it reaches maturity its appearance undergoes considerable alteration. It is then about two inches long, and moderately hairy; and while the body varies in tint from a pale yellowish green to a flesh colour, the head is now red, irregularly sprinkled with some black spots, and the prothorax is of a velvety black, though sometimes white predominates. The head, be it said, is polished
and sessile, and never set on the body by means of a narrow neck. But these larvae differ much from each other in size, marking, and colour, more so than ordinarily occurs with larvae of the same species.
Eventually the larva spins an oval cocoon of dirty yellow silk, of which the threads are so few, and so loose, as to allow the inmate to remain visible through the meshes; within the cocoon it changes to pupa. The chrysalis is not at all angular, and, moreover, reposes in a horizontal position. Yet it agrees with that of most diurnal Lepidoptera in being rather gaily coloured. Soon from the lowly motionless pupa arises the aerial imago, whose flight, which is truly diurnal, is swift, always strong, and in starts. The interior of the island it does not seem to haunt, but may be found plenteously in gardens at a distance of two, and even three, leagues from the shore, sporting in the sunshine, and sipping from the flowers of odoriferous trees of small stature. But it is by far the most common near the sea, because there grows its favourite Omphalea. As a matter of fact, however, it prefers flitting about the leaves of Coccoloba twifera, unless when employed in depositing its eggs. About midday, and in hot weather, it is addicted to soaring particularly high, and surmounts the tops of the tallest denizens of the forest, tending as winter comes on to relinquish such ambitious flight,
since it alights at times on hedges, offering, of course, a better chance of securing specimens.
As the genus Omphalea is common in Brazil and Guiana, in all probability it affords pabulum to Urania braziliensis and U. leiltis, species whose habitats are Brazil and Cayenne and Surinam, respectively; for, as MacLeay has remarked, " the minor natural groups of Lepidoptera often keep very constant to the same natural group of plants." Omphalea triandra, which is very widespread in Jamaica, is doubtless also the cradle of the Jamaican Urania sloamis. U. ftdgens, native to Columbia, Central America, and Mexico, certainly lives on arborescent plants of this genus. In a word, the gorgeous Madagascar Chrysiridia madagas-cariensis, the species of the East India isles, and many more, may likewise feed on leaves of seaside Euphorbiaceae. Captain King, in his " Narrative of a Survey of the Coasts of Australia," describes having found one of the insects in immense numbers about a grrove of Pandanus trees, growing on the banks of a stream which empties itself into the sea near the extremity of Cape Grafton on the north-east coast of New Holland. But MacLeay has " little doubt this species fiitted about the Pandani as U. fernandince {boisdtivalii) does about Coccoloba, while its eggs and larvae might have been found on the neighbouring Euphorbiacese."
DAY-FLYING MOTHS.
Migration of Day-Flying Moths.
Remark the habit of these day-flying moths of per-forming- migrations. The very beautiful Urania fiilgcns migrates annually, from east to west, in August and September, across the Isthmus of Panama. Flights have been observed by a naturalist in the Isle of Caripi, near Para in the Brazils, at Pernambuco, at Rio Janeiro, and in the Southern States of America; but he saw them nowhere so abundant as on the Amazons. From early morning till nearly dark, the insects passed-along the shore in amazing numbers, but most numerously in the evening, and mainly, from west to east. Swainson, speaking of U. brazilicnsis, a species almost the exact counterpart ot U. Iciius, describes having witnessed a host flying during the whole of a morning in June past Aqua Fria (Pernambuco), in a direction from north to south—not one deviating from this course, notwithstanding the flowers that were growing around; and though they flew near the ground, they mounted over every tree or other high object which lay in their path, and it was impossible to capture a single specimen, so rapid was their flight. For three or four days they continued to pass in this manner. On the occasion of the flights over the city of Panama, in some cases the insects are attracted into houses by the light, so as to almost fill
the rooms. They are accompanied by goat-suckers at night, and during the day by swallows and swifts, which probably destroy large numbers. As will be gathered, these migrations of Urania, though regular, are confined to comparatively narrow limits in the
tropics.
CHAPTER X.
THE CASE MOTHS (PSYCHID.ii).
Strange and Abnoivnal Lepidoptera.
It seems an incontrovertible fact in natural history that there is not a single character which has been used to distinguish any group of considerable extent from which some one or more of the members thereof may not depart. In that great division of the animal kingdom characterized by the possession of articulated limbs, many species are met which are entirely wanting in those organs; and, similarly, the secondary division of the Annulosa, marked by the presence of wings in the final Ptilota of species state—the Aristotle—contains that, throughout life, never acquire instruments of flight. Of wingless insects, indeed, examples might be drawn from most of the orders, and in the majority of cases, the females only are thus deprived. Rarely, however, both the orreat characteristics are absent. Yet certain moths do not possess articulated feet in the wingless
state. Consequently, if we took into consideration merely
the adult state of the females, this group must be regarded as among the most degraded instances of apiropodous insects. But such a conclusion cannot be maintained, as shown by an examination of the early stages of the moths, for these, we find, exhibit as high an amount of organization as those of any of the other insects appertaining to the order. The truth is, these females thehave become degenerate — very different from creatures they once were. Their peculiarity consists in this, that whereas, as a whole, winged insects always undergo a gradual evolution of structure, by which ultimately legs and wings are developed, these individuals gradually lose their powers of evolution, and not only this, but suffer a process of deterioration, by which the limbs which they at first possessed diminish, and at length dwindle altogether away, until the animal becomes a mere short, inert, vermiform bag, having not only no distinct trace of legs and wings, but also the sense-organs, the antennae, and the organs of the mouth are almost or entirely obliterated, and even the articulated condition of the body has almost disappeared. In these extreme forms it is hardly possible for the degeneration of the female to proceed farther, and in all doubtless the change has occupied an immense period. Than these extraordinary moths, familiar to German entomologists under the name of Sacktragers, perhaps
no more curious and interesting examples occur among the whole of the insect races; certainly, in structure of the female, and in habit, they are the strangest and most abnormal of all Lepidoptera. They belong to the Psychidae, a portion of the remarkable silk-spinning family of the Bombycidse, but offer many points which are distinct in themselves, and entitle them to rank, as recent lepidopterists agree, as a separate and well-defined tribe.
Their geographical distribution is extensive, since they are found in Europe, in North and South America, the West Indies and Mexico, in Northern India and Ceylon, in China, the South Sea Isles, and Australia, being most abundant in sub-tropical regions. Wonderfully few species are described as natives of the United States; while in California, unfortunately three have been discovered solely in the larval state, the more mature conditions of the species as yet eluding detection. But there, as in various other parts of the globe, probably greater numbers await the industry of observers. Among English-speaking folk the common appellations for the moths originate in the same circumstance as the popular term in Germany; house-builders, sack-bearers, basket-carriers, basket-worms, case-moths, — by these names they pass in England, America, and Australia, on account of the singular habitations, or sacks, they
2o6 TRUE TALES OE THE INSECTS.
weave for the well-being of the caterpillars, in the early staofes of their grrowth. Throug^h the whole of their larval life they carry the protecting structure about with them; and as regards the apterous female, she never leaves this home in which she dwelt while in larva one of the oddest incidents in this odd economy—but reaching maturity, and bringing forth her young, dies at last, without once quitting her self-constructed prison. She deposits her ova, an immense number, within the body of the case, closely enveloped in some species in a short silky down; and almost as soon as the larvce are hatched, they force their way out of the puparium which served for the defence of the eggs, deserting their early abode, and going forth into the world to follow independent lives. Escaping in crowds from the lower end of the tube to some twig or leaf, they immediately commence to prepare for themselves each a separate case, arranged in every respect as the larger ones, even before they have taken food.
Young Sack-bearer'S at Home.
The caterpillars manifest marvellous ingenuity in the construction of their cases. Particles of wood or bark, leaves, sticks, straws, lichens, mosses, and other vegetable
Fig. 39— l.arva case [JMctura doiigata), from Sydney,
substances, form, among the different species, the outer covering or decorative fortification of the house; the
2o8 TRUE TALES OF THE INSECTS.
interior is lined with soft silk, and interwoven silky threads likewise bind together the externeJ fragments. In the building materials chosen, and their arrangement, Mettira elongata is a most interesting architect (see
Fig. 39). Strengthening the large, elongate ovate bag of silk, and worked into it irregularly, appear numerous rows of short sticks, rather distantly separated, and about half an inch long, generally speaking; but towards the lower end there are usually several sticks from one to four inches long, in the centre of which the lower end of the silken bag protrudes, free from sticks, and very flexible. It has a charming silky softness, and is of a grey, ash, or mouse colour. Of this beautiful tissue the upper or head extremity is also composed; forming a tube half an inch wide. In the case of the Lictor Moth {Entoiiieta ignobilis), consisting of a cylindrical bundle of slender bits of straight twig, about an inch in length, the sticks, as in the previous instance, are fixed longitudinally by the whole inner side to the flexible silken lining; the title Lictor is suggested by the resemblance between the cases and the fasces, or bundle of rods, borne by the lictors of old before the consuls. But a third Australian, huebnci'i hy r\3.n\Q, has a case covered extern-A nimula ally with a vast number of very slender twigs affixed to it by one end only, the other being free. Here we perceive an admirable piece of instinct, the loose points of the twigs being always directed backwards, so that