62 MOSQUITOES OF NORTH AMERICA 



on different parts of the wing ; they offer excellent characters for specific dif- 

 ferentiation. Also the scales of the wing may be of different colors, either 

 irregularly distributed or forming a definite pattern, as in many species of 

 Anopheles. The vestiture is heaviest in the costal region, and the several series 

 are often crowded and overlapping ; sometimes there is a series of coarse scales 

 which project spine-like from the costal margin. The wing-membrane is usually 

 clear and transparent ; sometimes, however, it is inf uscated, particularly along 

 the costa. Such inf uscation is usually diffused over the entire wing. Sometimes 

 the inf uscation occurs in diffused spots in the region of the cross- veins, and else- 

 where, as in certain species of Culiseta. 



The shape of the wing often differs in the two sexes and the wing of the male 

 is then smaller and narrower. The narrowing of the wing of the male is often 

 very marked and is accompanied by differences in the proportions of the veins ; 

 particularly is there a tendency to crowding towards the costa and to the re- 

 duction of the second marginal and second posterior cells. When the male has 

 much narrowed wings the scales are often very deciduous. 



THE LEGS. 



The legs are long and slender. They are composed of trochanter, femur, 

 tibia, and a tarsus of five joints. The trochanters are short, jointed with the 

 coxae above, and with the femora below. They are freely movable upon the coxa 

 but they are rather closely united with the femur and there appears to be but 

 little motility at that point. 



The femora are always long but show considerable variation in the different 

 forms. Usually they are nearly alike in all three pairs of legs and are sub- 

 cylindrical or compressed. In Anopheles they are very long and slender and of 

 nearly equal thickness throughout. In Psorophora ciliata the femora are some- 

 what thickened towards their apices. In many forms the femora are compressed 

 and more or less enlarged. This enlargement is usually most pronounced in the 

 front and middle pairs; the middle femora, furthermore, are often fusiform, 

 largest above the middle. In some Sabethids the front femora only are 

 thickened. All three pairs of femora are usually of very nearly equal length. 

 In most forms the middle femora are slightly longer than the other two pairs. 

 In the Sabethini the hind femora are the shortest, in many forms appreciably 

 so, and this characteristic is usually more marked in one sex or the other. In 

 Sabethes the middle femora are much the longest. The femora are armed mth 

 a group of spines at their apices which differ in character and arrangement in 

 the different genera. There are also longitudinal series of setse, varying in num- 

 ber and coarseness. In Megarhinus these setae are represented by spines. 



The tibiae are slender and of approximately the same length as the femora. 

 They are subcylindrical and slightly thickened apically. This thickening is 

 most marked in the hind tibiae. In the Culicini the three pairs of tibiae may be 

 subequal in length, or the front pair may be markedly shorter. In the Sabethini 

 the hind pair of tibiae are always the shortest, although this character varies in 

 degree with the species and the sex; they are also stouter and more incrassate. 



