d_, _d_, mandibles; _e_, hypopharynx;
_f_, _f_, maxillae; _g_, labium; _h_, labella. (After Manson.)]

[Illustration: FIG. 67--Cross-section of proboscis of female (_a_) and
male (_b_) mosquito. _lxe_, labrum-epipharynx; _mn_, mandibles; _mx_,
maxillae; _hp_, hypopharynx; _sal_, salivary duct; _li_, labium; _tr_,
trachea; _mus_, muscles. (After Nuttall and Shipley.)]

THE MOUTH-PARTS

The mouth-parts of the mosquito are of course of particular interest to
us. At first they appear to consist of a long slender beak or proboscis,
but by dissecting and examining with a microscope we find this beak to
be made up of several parts (Fig. 66). The labium, which is the largest
and most conspicuous, is apparently cylindrical but is grooved above
throughout its length. At the tip of the labium are the labellae, two
little lobes which serve to guide the piercing organs. Lying in this
groove along the upper side of the labium are six very fine,
sharp-pointed needles. The uppermost of these, the labrum-epipharynx, or
labrum as we will call it, is the largest and is really a hollow tube
very slightly open on its under side. Just below this is the
hypopharynx, the lateral margins of which are very thin. Down through
the median line of the hypopharynx runs a minute duct (Fig. 67, sal)
which, though exceedingly small, is of very great importance, for
through it is poured the saliva which may carry the malaria germs into
the wound made when the mosquito bites. The other four needles consist
of a pair of mandibles which are lance-shaped at the tip and a heavier
pair of maxillae, the tips of which are serrate on one edge.

HOW THE MOSQUITO BITES

When the female mosquito is feeding on man or any other animal the tip
of the labium is placed against the surface and the six needles are
thrust into the skin, the labellae serving as guides. As they are thrust
deeper and deeper the labium is bowed back to allow them to enter. As
soon as the wound is made the insect pours out through the tube of the
hypopharynx some of the secretion from the salivary glands and then
begins to suck up the blood through the hollow labrum into the pharynx
and on into the stomach.

The mouth-parts of the male differ in some important respects from those
of the female. The hypopharynx is united to the labium, the mandibles
are wanting and the maxillae are very much reduced so that the insect is
unable to pierce the tough skin of animals. The male feeds on the