Page:Insects - Their Ways and Means of Living.djvu/394



threadlike and provided with comparatively few short hairs (A). The sexes differ also in the mouth parts, for, as in the horseflies, the males lack mandibles. The mouth parts of the mosquito, in the natural posi- tion, do hot appear as separate pieces, as do those of the horseflv. The various elements, except the palpi, are com- pressed into a beak that projects forward and downward from the lower part of the head (Fig. 176 A, Prb). "l'he length of the beak varies in different kinds of mosquitoes; it is particularly long in the large South American species shown in Figure 76. When the beak of the female mosquito is dissected (Fig. 76 B), the same equipment of parts is revealed as is possessed by the female horsefly IFig. 69 B), namely, a [abrum (Lin), two mandibles (.(ld), two maxil[ae (.1Ix), a hypopharynx (Hph.v), and a labium (Lb). It is the labium that forms most of the visible part of the beak, the other pieces being concealed within a deep gro«ve in its upper surface. The la/rivera (Fig. 176 B, Lin) is a long median blade, concave below, terminating in a hard, sharp point; it is probably the principal piercing tool of the mosquito's outfit. The mamtib/es of the mosquito (:lld) are very slender, delicate bristles; those of the species figured are so weak that it would seem they can be oflittle use to the insect. The maxi//ae (Mx) are thin, fiat organs with thickened bases, each terminating in a sharp point armed on its outer edge with a row of backward-pointing, saw- like teeth which probabl.y serve to keep the mouth parts fixed in the puncture as the perclng lalrum is thrust deeper into the flesh. "Fhe pa/pi I.IlxP/p) arise from the bases of the maxillae. The h)'popha?mx (lqpk),) is a slender blade with a median rib which is traversed by the channel of the salivary duct. |ts upper surface is con- cave and, in the naturai position, is closed against the concave lower side of the labrum, the two apposed pieces thus forming between them a tube which leads up to the

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