Sucking mouth-parts, forming a “proboscis” made up of the two very long maxillæ, spirally rolled up under the head when not in use (Fig. 92), and adapted for sucking honey. There are some forms which take no food in the adult condition, and in which the proboscis is short; in a few species of hawk-moths, this organ is even longer than the body. The larvæ (“caterpillars”) have biting mouth-parts. The body of a butterfly or moth is covered with hair-like structures developed by the skin; in the wings these are broader, have a characteristic appearance (Fig. 93), and partially overlap one another. These scales cause the colours of the wing. They can easily be wiped off, leaving the corresponding part of the wing transparent and clear as glass. In many species (all hawk-moths, many owlet moths) there is a _wing-hooklet_, i.e. the hind wing has a spine or a thick brush which grasps a band-like area of the fore wing. In this way the two pairs of wings are held together. The females of a few species of spinner and looper moths are wingless, or only possess short flap-like wings useless for flight. The metamorphosis is complete (p. 89); the larvæ are true caterpillars; the pupæ are obtectate (p. 93). Many caterpillars creep into the ground to become pupæ, and spin no investment at all (_e.g._ hawk-moths). Others make a cocoon, which may consist of threads loosely woven together or may be of firm texture (Fig. 60). The cocoon consists chiefly of silk, a substance secreted in a spinning gland, and exuding to the exterior on the lower lip; but minute particles of sand or earth, and fragments of wood gnawed off by the caterpillar, may be stuck in the cocoon. The pupæ of butterflies are naked, without cocoon, but are fixed by threads to leaves, tree stems, walls, hedges, etc. A distinction is drawn between girdled and suspended pupæ; the first are fixed by a silk band, which surrounds them, and the head is directed upwards, while the latter are suspended by the tip of the abdomen (Fig. 94). The time required for the development of the perfect insect from the pupa is not always the same, depending not only upon the species, but also upon the time of year. The summer generation of the large white spends scarcely fourteen days in the pupa stage, the winter generation eight months. Family: =Diurna= (_Butterflies_). Body relatively weak and thin; wings very broad, not very long relatively. No wing-hooklet (_see above_). Wings folded together above in a state of rest, so that their upper sides touch. Antennæ thickened in a club-like way at the tip. The caterpillars possess five pairs of pro-legs; they are usually almost devoid of hair. There are, however, a few (_e.g._ the caterpillar of the peacock butterfly, Fig. 94) which possess hard, spine-like, much-branched bristles. The naked pupæ are sharp cornered; some are girdled, others suspended (p. 137). [Illustration: