The _compound eyes_, seated on each side of the head, extend from the vertex generally to the articulation of the mandibles or jaws, their longitudinal axis being perpendicular to the station of the insect. They vary in external shape and convexity in the several species and genera, although not greatly, and consist of a congeries of minute, hexagonal, crystalline facets, each slightly convex externally, and their interstices are sometimes clothed with a short and delicate pubescence. Each separate hexagon has its own apparatus of lens and filament of optic nerve, each having its own distinct vision, but all converge to convey one object to the sensorium. The function of the compound eyes is concluded to be the microscopic sight of near objects. The _face_, which sometimes has a longitudinal _carina_, or prominent ridge, down its centre, lies between these eyes, descending from the vertex to the base of the clypeus, or nose, but which is without the function of that organ. This clypeus is sometimes protuberant, and from shape or armature, characteristic. This part, however, is not always distinctly apparent, although a line or suture usually separates it above, from the face. At its lower extremity the _labrum_, or upper lip, articulates, over which it is sometimes produced; and it extends at each lateral apex to the base of the insertion of the mandibles. The _genæ_, or cheeks, descend from the vertex laterally, behind the compound eyes, to the cavity of the head which contains the lingual apparatus, when folded in repose. These cheeks, at their lower extremity, sometimes embrace the articulation of the mandibles. [Illustration: Fig. 6.—1, Clavate antennæ; 2, filiform ditto; _a_, scape; _b_, flagellum.]