Lepidoptera is an order of the class Insecta, comprising the butterflies and moths. The name was given to the order because the wings are covered with little scales, or flattened hairs. The Lepidoptera undergo in their development a complete metamorphosis, passing through the stages of the egg, larva and pupa, before appearing as the perfect insect, or imago.
Eggs.—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.
Larvae.— When the eggs hatch the insects appear as larvae, or caterpillars. These undergo successive molts as they increase in size, shedding their skins from time to time until they have attained the development at which the next transformation, known as pupation, occurs. The bodies of larvae consist normally of 13 segments, or somites, of which the first is the head.
Pupae.— When the larva has attained maturity it is transformed into a pupa. Pupae may be naked, or they may be enclosed in a structure of silk known as a cocoon. The pupas of butterflies are usually attached by their anal extremities 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 addition held in place by a girdle of silk.
The Imago.— When the period of pupation is ended the butterfly or moth breaks through the pupal shell and emerges a four-winged, six-footed insect, known as the imago. The females of some species of moths are apterous, or provided with wings so poorly developed that they cannot be used in flight.
