Head of Ripipteryx, Æ, epicranium. EE, eyes. æ, clypeus. a, labrum. CHAPTER II. ON THE HEAD, LEGS AND WINGS OF INSECTS. y y, antennæ. HAVING described the shell, frame, or skeleton of an insect, and its division into segments, we must next give our attention to those parts which, though strictly portions of the skeleton, may be conveniently treated as its appendages, and we will examine these in the order in which they occur, beginning with those of the first segment. Previously however to describing the appendages of the head, it may be useful to take a cursory view of the head itself. Looking at the above figure, we shall observe it possesses a considerable similarity to the skull of some quadrupeds; the arched top may be considered to represent the crown of the head; the space in front, Æ, the forehead; the lateral spaces, EE, the eyes: the plate below the forehead, æ, represents the nose, and is so called by Kirby, the lower extremity of it being termed by Mr. Kirby the rhinarium or nostril-piece, probably from its frequently covering the base of the antennæ, y y, which in situation are precisely similar to the nostrils of vertebrate animals: below this plate is the upper lip, a, and immediately under this is the aperture of the mouth, the space on each side of the nose is analogous to a cheek. Mr. Kirby's nomenclature of the parts of insects is drawn from these analogies with similar parts in superior animals, but so many of his presumed analogies appear fanciful or farfetched, that his nomenclature has been universally rejected. It is supposed that the head of insects, like the following segments, is composed of four smaller portions or sections; in this instance, however, they are not merely distinguished by sutural lines, but perfectly separated and freely articulated: these are the skull or cranium, the upper and lower lips-labrum and labium, the feeler-jaws or maxillæ, and the jaws or mandibles, mandibule: the lips, jaws, and feeler-jaws, constitute the mouth of an insect. If we were to assign to these parts names in accordance with those of the pro- meso- and metathorax, we should call the jaws the præscutum, the feeler-jaws the scutum, the lips the scutellum, and the skull the postscutellum. Some writers have suggested that the divisions of the head are of equal importance with the following segments, and allowing three or sometimes four segments for the head, have increased the total number to fifteen or sixteen. Each section of the head has a tendency to produce two feelers: on the last-the mandibles-they are obsolete; on the skull, lips, and feeler-jaws, they are very distinct: in the lobster and other animals resembling it, which are closely related to insects, the mandibles are furnished with distinct feelers. The skull consists of four portions; the superior arched upper surface, A, is the crown, epicranium or vertex, the inferior surface, B, in the figure at page 153, is the throat or gula, and the lateral surface, E E, are the eyes or oculi. The epicranium is frequently divided by a sutural line, passing across the forehead from eye to eye. When this is the case, the portion so separated, æ, and which immediately covers the mouth, and in many instances the antennæ also, is called the shield or clypeus; the gula also is often separated by a similar sutural line; in this case, the anterior portion adjoining the mouth is called the chin or mentum. There are one, two, or three minute, transparent, highly convex lenses situated on the crown of the head, into which they are closely soldered; these are called simple eyes or ocelli: all insects, except beetles, seem to possess them more or less perfectly, and in several species even of beetles ocelli have been detected; the situation and comparative size of these is shown by the three black spots in the skull of Ripipteryx; their use has never been ascertained, but entomologists agree in considering them organs of vision. Antenna.-The cranial feelers or antennæ, y y, arise from the skull in front of the ocelli, between the eyes, sometimes above and sometimes below the clypeus; they are freely articulated with the skull, and moveable in every direction; they are composed of numerous joints. In length, stoutness, shape and clothing, the antennæ of insects are very various; their variations are the subject of nomenclature; and, moreover, afford excellent characters for descriptions. Antennæ are called setaceous (fig. 1), attenuantes, when they are long, throughout slender, and yet taper gradually to the apex, and the union of the joints takes place without any marked indentation or protuberance: filiform or filiformes (fig. 2), when stouter 1 : and shorter, and preserving throughout a uniform substance': incrassated or accrescentes (fig. 3), when resembling the last, excepting that they gradually increase in substance towards the apex: fusiform or fusiformes (fig. 4), when stoutest at the middle and tapering very gradually to each end: moniliform or moniliformes (fig. 5), differing from the filiform in one character only; each separate joint is oval or globose, and the portion connecting it with the next joint is very slender; the joints thus resembling beads on a string serrated or serrate (fig. 6), having each joint produced on one side at the apex, so that together they resemble the teeth of a saw: pectinate or pectiniformes (fig. 7), in which the joints are still more produced, or rather, are furnished on one side with slender processes, resembling, in some degree, the teeth of a comb: flabellate or flabelliformes (fig. 8), having the processes of the joints still longer, very thin, and, when at rest, lying flat on each other, like the folds of a fan; the antennæ of some insects are flabellate throughout, others have only the apical portion flabellate: in the latter case they are termed lamellate or lamellate (fig. 9); this form is not uncommon, the whole of the Linnean genus Scarabæus, possessing this structure, and thence being now 11 14 11 universally termed Lamellicorns or Lamellicornes; this form of antennæ is subject to great variation, and the variations afford excellent characters for distinguishing the genera into which the Linnean Scarabæi are now divided: ciliate or fimbriata (fig. 10), in primitive structure, are setaceous; but each joint is furnished on each side with a single hair: elbowed, kneed, or broken, technically fractæ (fig. 11), have one joint, usually the second from the base, very long, and the remaining joints attached to it at a right angle: pilose or pilose, when covered entirely with a soft down: setose or setosæ (fig. 12), when furnished throughout with irregular, harsh, bristly hair: plumose or plumosa (fig. 13), when setigerous, but furnished with long downy hairs, which give them the appearance of a feather: ramose or ramosa (fig. 14), when of setaceous or moniliform structure, but having several joints near the base produced into long branches, sometimes nearly equalling the antenna itself in 18 17 16 17 18 12 length: bifurcate or bifurca (fig. 15), when composed of three joints, of which the apical one is very long, bent double, and attached at its centre to the second joint: clavate or clavigera (fig. 16), when terminating in a gradual club, the shaft being generally long, slender, and filiform capitate or capitate (fig. 17), in which the knob is more abrupt, and strongly marked; the knob is some |