Page:Tropical Diseases.djvu/180

148 ethrinæ, in which the proboscis is short and not formed for piercing; and (2) Culicinae, or typical mosquitoes with elongate proboscis. The Culicinæ again are arranged in four natural tribes according to the table. Most workers at the group now regard the Anophelini as naturally definable in a single genus, Anopheles, which may be characterized as follows:——

Head only moderately broad, usually covered with upstanding forked scales, though scales of other kinds are also present in a few species. Maxillary palps long and spathulate in the male; as long as, or not much shorter than, the proboscis in the female. Free edge of scutellum simply convex, not trilobate; metanotum bare. Abdomen either sparsely hairy or with localized patches of scales; sometimes with a considerable expanse of scales which, however, never form a uniform, complete, and compact investment. Wings commonly dappled or profusely speckled, but occasionally quite spotless. Legs remarkably elongate. In repose the body is usually inclined at an angle with the resting surface.

The eggs are boat-shaped, and with rare exceptions have their investing membrane inflated laterally to form a pair of floats.

The larva has the head at least as long as broad, and has four bristles or feathered hairs projecting from the free edge of the clypeus. The long lateral hairs of the thorax and abdomen are strongly feathered. Some or all of the abdominal segments as far as the 7th carry dorso-laterally a pair of characteristic rosettes or cockades of scales. The breathing openings are situated in a hollow on the dorsum of the 8th segment, the hollow being bounded laterally and posteriorly by a system of folds or valves.

The larvæ occur not only in all kinds of stagnant water, but also in pools in the beds of rivers and mountain streams, or even in the current if there is also floating weed and debris for their protection, in