Entomology for medical officers / by A. Alcock.

  • Alfred William Alcock
Date:
1920
Catalogue details

Licence: In copyright

Credit: Entomology for medical officers / by A. Alcock. Source: Wellcome Collection.

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    absent; and in males generally both mandibles and maxillae are wanting (Fig. 13). The thorax, which is scaly or hairy, is formed chiefly by the middle segment (mesothorax). In a dorsal view little is seen but the scutum and scutellum, the latter usually having its free edge trilobate, but sometimes (.Anopheles) simply curved. In front of the scutum, on a lower plane, the dorsal element of the prothorax shows as a pair of shoulder-knots. Overhung by the scutellum lies the meta- notum, usually quite bald. The elongate abdomen, which also is scaly or hairy, consists of 9 visible segments, the last of which is considerably retracted and bears a pair of lobes or cerci, the lobes in the female being simple, but in the male complicated and terminating in paired hooks or claspers. The wings are elongate and narrow and have the venation shown in Fig. 9, a noticeable feature being the short 3rd longitudinal vein taking off from the second at such an angle that its origin is sometimes spoken of as a “ supernumerary cross-vein.” Characteristic also is the double or triple fringe of scales along the hind border. Except in the small subfamily Corethrince, where hairs generally take their place, all the veins are clad with scales. There are no squamae, so that the halteres are conspicuous. The legs, which are invested with scales, are long and slender, and the first tarsal segment is as long as or longer
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