But of all the moths of the tribe Born byx, the P. mori, or silk-worm moth, is by far the most important. This is a whitish moth, with a broad pale brown bar across each of the upper wings. The caterpillar or larva, emphatically known by the title of the silkworm, is, when full grown, nearly three inches long, and of a yellowish grey colour : on the upper part of the last joint of the body is a horn-like process, as in many of the sphinges. It feeds, as every one knows, on the leaves of the white mulberry, in defect of which may be substituted the black mulberry, and even, in some instances, the lettuce, and a few other plants. The silkworm remains in its larva state about six weeks, changing its skin four times during that period, and, like other caterpillars, ab staining from food for some time before each change. When full grown the ani mal entirely ceases to feed, and begins to form itself a loose envelopement of silken fibres, in some convenient spot which it has chosen for that purpose, and afterwards proceeds to enwrap itself in a much closer covering, forming an oval yellow silken case or ball about the size of a pigeon's egg, in which it changes to a chrysalis, and after lying thus inclosed for the space of about fifteen days, gives birth to the moth. This, however, is always carefully prevented when the animals are reared for the purpose of commerce, the moth greatly injuring the silk of the ball by discharging a quantity of coloured fluid before it leaves the cell ; the silk balls are therefore exposed to such a degree of heat as to kill a few only being saved fbr the breed of the following year. The moth, when hatch ed, is a very short-lived animal, breeding soon after its exclusion, and when the fe males have laid their eggs, they, as well as the males, survive but a very short time.
As an example of the Geometrx, we may adduce a very elegant moth, often seen towards the middle of summer, in Europe, on the elder, and called P. sam bucaria ; it is moderately large, of a pale sulphur colour, with angular wings, mark ed by a narrow transverse brown line or streak It proceeds from a green cater pillar, which, like those of the rest of this section, walks in a peculiar manner, viz. by raising up the body at each progres sive movement into the form of an arch or loop, the extremities nearly approaching each other. It changes in May and June
into a black chrysalis, out of which in June or July, proceeds the moth.
The division called Tinex comprehends those moths which are, in general, of a small size, though often of very elegant colours. Of this tribe is the P. padella! it is of a pearly white colour, with very numerous black spots : its caterpillar is gregarious, appearing in great quantities on various sorts of fruit trees in Europe during the decline of summer, and com mitting great ravages on the leaves : these caterpillars inhabit a common web, and usually move in large groups toge ther ; tieir colour is a pale greyish yel low, with numerous black spots ; each caterpillar at the time of its change to Chrysalis, envelopes itself in a distinct oval' web with pointed extremities, and many of these are stationed close to each other, hanging in a perpendicular direc tion from the internal roof of the gem ral inclosing web : the chrysalis is blackish, and the moth appears in the month of Sep tember. To this division also belong the moths, emphatically so called, or cloth moths. Of these the principal is the P. vestianella, which in its caterpillar state, is very destructive to woollen cloths, the substance of which it devours, fbrming for itself a tubular case with open extre mities, and generally approaching to the colour of the cloth on which it is nourish ed. This mischievous species changes into a chrysalis in April, and the moth, which is universally known, appears chiefly in May and June.
In the last division, called Alucitx, is one of the most elegant of the insect trihe, though not distinguished either by large size or lively colours. It is a small moth, of a snowy whiteness, and, at first view, catches the attention of the observer by the very remarkable aspect of its wings, which are divided into the most beautiful distinct plumes, two in each tipper, and three in each under wing, and firmed on a plan resembling that of the long wing feathers of birds, viz, with a strong rib or shaft, and innumerable lateral fibres. This moth, which is the P. pen tadactyle of Linnzus, an European spe cies, appears chiefly in the month of Au gust. Its caterpillar, which is yellowish green, speckled with black, feeding on nettles, and changing into a blackish chry salis enveloped in a white web.