STRICTURE. The head in this group is distinct from the thorax. clothed with hairs, and bears large, compound eyes. and moths have also sim ple eyes (ocelli). The antenna- are always pres ent, and important not only as feelers. but as organs of hearing and smell (set. INSECT). the latter service being probably a very important one in this group. These antennae take various shapes. Among hottertlies they are thickened at the end, sometimes into a rounded club. but Inure often into a spindle-shape terminating in a bent point. Of the moths "some have thread like antenna tapering to a tine point; others have feather-shaped antennae: others still have antenme which are prismatic in form, and pro vided with a little hook or spur, at the end: and there are many modifientions and variations of these forms." The shape, or at least the size, usually varies between the sexes. being larger in the male than in the female—a fact connected with his duty to search for her, and especially observable in moths. The same may be said of the eves. which, in the nocturnal species, cover the whole side of the head and have an enormous number of facets-27,000, it is said, in some hawk-moths.
The mouth in the Lepidoptera is modified into a sucking-organ, enabling this insect to feed on the nectar of flowers and the sap of trees and plants. The mandibles are rudimentary or ab sent, and the maxilla.. by a very extraordinary development and modification. are formed into a sinking-tube, called the proboscis, which, when not in use, is coiled up between two forward projecting organs, the labial paipi. It is "com posed of three distinct hollow tubes, soldered to each other along their inner margins." and "has much the appearance of a double-barreled gun. with a third tube lying below." Nutrition is imbibed through the lower or central tube. by a regular pumping. produced by the alternate muscular pinching and loosening of a bulb-like arrangement in the head: and the other tubes admit air. In sonic of the sphinx-moths the proboscis may be ten inches long, and in others its tip is armed with spines which serve to break or cut the surface of fruits, the juice of which is sucked lip.
Wings.—The thorax bears the legs and wings. The former are weak and are merely used as organs of support when the insect is at rest, and the front pair of legs may be short or rudimen tary, as is the ease in Vanessa. The four mem branous wings are usually large in comparison with the sine of the body; expanse of wing and strength of flight, however. are not exactly cor related, for some of the hawk-moths with pro portionately small wings are the most enduring flyers, yet the large-winged forms probably thy with less exertion. In actual size lepidopterans vary from almost microscopic species. hiding in the moss, to tropical monarchs 12 inches in ex panse. These transparent membranes are sup ported by a framework radiating from the thoracic joints, which consist of double horny tubes (veins or 'nerves' and nervules) one within the other, the inner being filled with air and the outer with nutritive fluids. "These 'nerves,' as
custom will persist in terming them, in the but terflies, take a bow-like or ellipsoidal sweep from the base of the wing. forming what is the 'discoi dal cell,' whence there branch off to the edges a.
series of horizontal. almost parallel, slightly di vergent ner•ules. On the posit hm of these the identification of species is most securely based. . . . In the moths• on the other hand. the dis coidal cell is less conspicuous." The names of the parts of the wing, and of its veins and nervules, used by entomologists in their descrip tions of species. are given in the accompanying illustrations. To further increase the power of the pinions. the pair on each side are made to act as one. This adjustment is effected either by an overlapping of the hind wing by the front wing (butterflies or some of the larger moths.) or the posterior wing possesses a 'frenulum.' composed of one or more bristles, which fits into a 'retina culum.' a membranous flap or a bunch of scales on the anterior wing (other. moths). According to Hampson, "the form of the frenulum is of use in determining sex, as in the males of all the forms that possess it it consists of hairs firmly soldered together so as to form a single bristle, while in nearly all females it consists of three or more bristles, separate and shorter than that of the male." Scales.—The wings of all Lepidoptera, as the word implies, are clothed more or less completely with scales, which are modified hairs—hairs that are very short and much widened; and every gradation may be found, in a species like Itho myia. between the hairs on the body and wings and the scales. They are like small chitinous bags with the sides pressed together, and each one has on its proximal end a short stalk which fits into a cavity of the wing-membrane. They are of various shapes. notched on the posterior margin, striated, etc.. and "the males of ninny species have peculiarly shaped scales arranged in tufts and folds. which are called 'androconia,' and are useful in microscopically determining species." The scales are in rows, and overlap much as do the scales on a fish or the shingles on the roof of a house. They rub off easily, and entomologists know how to remove them with out serious injury; but when taken from a living insect they diminish or destroy its ability to fly. They number hundreds of thousands. and their use is to strengthen the membranous wings. and when they overlap the wing-membranes at the odges to a considerable extent, as occurs in some cases. they also increase the wing-area. Another use is to bear the colors of the wings, for when the scales are removed the color is gone. This color is due either to pigment contained within the scale or its walls, or to the tine striations on the upper surface which give rise to metallic `interference colors.' Both albinism and mela nism occur. The pigments are perhaps in the nature of biliary excretions, such as urates from nitrogenous matter and melanins front carbona ceous matter.