. Entomology for medical officers. Insect pests; Insects as carriers of disease. NEMATOCERA: HARMLESS NEMATOCERA 129 has a certain amount of resemblance to a Culicid larva, except that the thorax is not differentiated from the abdomen : it consists of a head with antenna, mandibles, and maxillse, and with mouth-brushes much like those of a Cu/ex larva, and of 12 body-segments ; on the dorsal surface of the penultimate segment of the body there is a pair of breathing- openings like those of Anopheles situated in a depression which is ^mouthhr. T^ni breathing op. ''.rang' 'pseudop. Fig. 34.—Larv
. Entomology for medical officers. Insect pests; Insects as carriers of disease. NEMATOCERA: HARMLESS NEMATOCERA 129 has a certain amount of resemblance to a Culicid larva, except that the thorax is not differentiated from the abdomen : it consists of a head with antenna, mandibles, and maxillse, and with mouth-brushes much like those of a Cu/ex larva, and of 12 body-segments ; on the dorsal surface of the penultimate segment of the body there is a pair of breathing- openings like those of Anopheles situated in a depression which is ^mouthhr. T^ni breathing op. ''.rang' 'pseudop. Fig. 34.—Larva of Df-ra. protected by stiff setose flaps ; on the ventral surface of some of the body-segments there are pairs of spinose pseudopods. The larva creeps about on aquatic vegetation close to the water's edge, and has the habit of carrying its body strongly bent; when submerged it swims by vigorous contortions. The pupa much resembles that of Culicida. I have received the larvas of Dixa as " worms" passed in the urine of a patient—caveat medicaior. Family RHYPHIDiE. This is a very small family but is widely distributed. One of the species, Rhyphus fenestralis (Fig. 35), is commonly found on windows and mistaken for a mosquito, or even, by reason of its spotted wings, for. Fig. 35.—Wing of miypliiis, an Anopheles. The antennae are of fair length, are composed of 16 segments, and do not carry whorls of hairs. In the wings there is a discal cell, and the 2nd longitudinal vein is not forked. In the legs the empodium is pulvillus-like, and the true pulvilli are vestigial. The larva is slender and worm-like. Family CecidomyiD/E : Gall-gnats (Gr. Ki;Kis=a gall; /tufa=fly). The species of this large family (Fig. 36) are small (often minute) delicate midges, with long (often moniliform and plumose) antennae, long slender legs, and broad, filmy, often hairy wings. The proboscis is generally short. The wings commonly have only three longitudinal veins, two of which are very
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