The butterflies are included in the Lepidoptera, and are the day-flying forms. There are many other insects equally beautiful, in more subdued tints, which are night flyers. These are the moths (Fig. 237), which are slow of flight, ponderous, and have extraordinary tongues for sucking the juices from the flowers. They can be distinguished from the butterflies by their feathered antennæ. One of the best known for its ravages is the dwarf moth, the worm of which plays such havoc among woolens. The cankerworm moth is equally a pest among valuable shade trees. Another familiar form is the hawk moth (Fig. 238), which so resembles a humming bird in appearance and motion that it is almost impossible to distinguish between the two, the moth being one of the most active, poising over flowers and inserting its enormous tongue to secure the sweets there concealed. A showy moth is the huge Attacus, its larva being especially large and voracious. [Illustration: FIG. 238.--Hawk moth, a rapid flyer.] [Illustration: FIG. 239.--Death's-head moth.] The moths display as great a variety in their shapes, colors, and sizes as the butterflies. The death's-head moth (Fig. 239) is perhaps as startling as any, bearing on its back a well-defined figure of a skull. The most valuable moth to man is the silkworm moth, the wings of which have a spread of six inches and are a brilliant ochre yellow, fawn, or mouse color, marked with striking peacock-like eyes. They deposit eggs, but the development of the caterpillar is somewhat different from that of the butterfly larva. The latter passes its pupa stage as an unprotected chrysalis attached to some object by the tail (Fig. 240), but the caterpillar of the moth secretes silk from a gland in its head, and with this forms about itself a cocoon. This is unwound by machinery and woven into the valuable silk of commerce. The silk industry brings to the weavers of the United States alone an annual sum amounting to about $30,000,000. The silkworm can easily be kept and all its changes watched, and many persons are interested in rearing the worms. The time required by the worm to form its silk cocoon varies with the locality. Thus in France it will complete it in four days, while in England forty or more days are necessary. About two hundred cocoons weigh a pound. [Illustration: FIG. 240.--Pupa of butterfly.] [Illustration: FIG. 241.--Basketlike cocoon of a South American moth.]