740 



CLASS IV. 1NSECTA. 



FIG. 472. Bud of labium, labrum and 

 epipharynx, mandibles and first 

 maxilla of Anopheles mamlipennis. 

 magnified (after Nuttall and Shipley). 

 1 labium ; 2 labrum and epi- 

 pharynx ; :', first maxilla ; 1 man- 

 dible ; 5 labellae. 



backward. In the male the mandibles are absent and the hypo- 

 pharynx has fused with the labium. 



The head is joined to the thorax by an unusually flexible neck. 



The segments of the thorax are 

 much fused and their limits diffi- 

 cult to make out. The wings are 

 membranous and, except in Culi- 

 cidae (Fig. 473), devoid of scales; 

 the " cells " are never numerous 

 (Fig. 366). Very frequently at 

 the posterior side of the base of 

 the wing a notch separates a 

 small lobe, the alula, from the 

 rest of the wing ; and still nearer 

 the base one or even two more 

 lobes may be seen called the 

 squama (or antitegula) and tegula. 

 These afford facilities for the 



folding back of the wing, which in 



repose lies almost always flat and un- 



crumpled on the abdomen. The hal- 



teres are small knobbed structures 



which like the wings can vibrate 



rapidly. They are apparently sensory 



in function and in some cases possibly 



stridulating. The legs are slender, 



usually hairy. The tarsus has almost 



a 1 \vays five segments, and terminates 



in two well-developed claws, under each 



of which is a free pad, the pulvillus ; 



a median empodium may also be pre- 

 sent between the claws. 



The abdomen may show as many as 



nine segments (Fig. 365) or as few as four. 



In the latter case a certain number of 



segments are withdrawn posteriorly 



into those in front and the first segment 



is concealed by the thorax. An ovipositor may be present. 

 In those Diptera which suck juices a powerful sucking pharynx. 



which expands under muscular effort, is found, also certain sacs 



FIG. 473. Scales on the edge of 

 the wings of Anopheles mticuli - 

 pennis, magnified (after Nuttall 

 and Shipley). 



