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Lepidoptera

larva, pupa, eggs, moths, silk, located, species and pupal

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LEPIDOPTERA (Gr. Relic, scale; IrreP4v, wing) : An order of the class Insecta, compris ing the butterflies and moths. The name was given to the order because the wings are covered with little scales, or flattened hairs. The Lepi doptera undergo in their development a com plete metamorphosis, passing through the stages of the egg, larva and pupa, before appearing as the perfect insect, or imago.

The eggs of the Lepidoptera are minute objects, though generally large enough to be seen with the naked eye. When examined under the microscope they are found to vary greatly in form according to the species. They may be spherical, hemispherical, oval, conic, cylindrical, spindle-shaped or flattened. The eggs of the Cochlidiides, or slug-moths, are cir cular, or elliptical, and greatly flattened, resem bling microscopic pancakes. The egg of the common cabbage-butterfly is spindle-shaped. The eggs of both butterflies and moths are generally beautifully fluted with raised lines, or ornamented with a net-work of sculpturings arranged in geometrical patterns. They are always provided with a minute opening in the shell known as the micropyle, permitting them to be fertilized. This is located at the apex in most forms, but in the case of those eggs which are flattened the micropyle is 'located on the side. The female deposits the eggs upon the plant on which the caterpillars feed, or in close prox imity to the food which is to nourish them, in the case of those few species which do not subsist in the larval stage upon vegetable matter.

Larva,— When the eggs hatch the insects appear as larva, or caterpillars. These undergo successive molts as they increase in size, shed ding their skins from time to time until they have attained the development at which the next transformation, known as pupation, occurs. The bodies of larva consist normally of 13 segments, or somites, of which the first is the head. The forms of the larva are very various, though in the main they are vermiform and cylindrical. The larva of butterflies are for the most part smooth, though in some genera they are curi ously ornamented with lateral or dorsal projec tions, which may be spinous, club-shaped or filamentous. The larva of moths are often hairy, or spinose, and in some genera of the Lassocampidcr, the Cochlidiiche and the Satur nadir, these spines possess stinging, or poison ous, properties. Lepidopterous larva possess three pairs of true feet located upon the three segments immediately following the head, and corresponding to the six thoracic feet which are found in the winged form ,of the insects.

In addition to these true feet the bodies of these larva are supported by from two to eight pairs of abdominal prolegs, or false feet, which are fleshy and do not recur in the imago. The head is always more or less conspicuous in the larval stage, and is provided with eyes and mouth parts adapted to cutting and deglutition.

One of the most remarkable portions of the anatomy of lepidopterous larva are the two long glands located in the dorsal region, which secrete a milky fluid, which is vented through a nipple-shaped organ upon the lower lip known as the spinneret, and which upon exposure to the atmosphere is transformed into the sub stance known as silk.

Pupa.— When the larva has attained ma turity it is transformed into a pupa. Pupa may be naked, or they may be enclosed in a structure of silk known as a cocoon. The pupa of butter flies are usually attached by their anal extrem ities to twigs, the under side of rails or stones. The attachment is effected by means of a button of silk into which the hook-like cremaster is thrust. In some families chrysalids are in addi tion held in place by a girdle of silk. The larva of moths undergo pupation in a cocoon may be densely woven or very loosely constructed of a few strands of silk mingled with hairs from the body of the caterpillar, or loose particles of adherent earth or fragments of leaves. Many of the hawk-moths and almost all of the owlet-moths undergo transformation in underground cells which the caterpillars mold for themselves in the soil before changing into pupa. The duration of the pupal stage varies in length according to the species, or the season. Many species in temperate climates pass the winter in the pupal form. Where there are two or more generations in a season the pupal period is short for the summer broods, and the fall brood hibernates in the pupal state. The pupa of butterflies are often ornamented with silvery or golden spots, hence the name chrysalis has been applied to them, the word being derived from the Greek (xs,puci6 gold). The pupa of moths are generally some shade of brown or black. The pupa contains the imago and in almost all cases an examination will show in the pupa the location of the vari ous organs of the perfect insect in a rudimen tary form.

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