50 ENTOMOLOGY FOR MEDICAL OFFICERS 



wing is always supposed to be extended at right angles with 

 the body) is beset with stiff bristle-like scales, and the hind 

 edge is ornamented by a characteristic fringe which consists 

 of scales of two forms, namely, short, broadish, closely 

 appressed border-scales, and long, narrow, outstanding fringe- 

 scales of two lengths. The characteristic features of the 

 venation are (i) that the subcostal vein is long; (2) that the 

 2nd, 4th, and 5th longitudinal veins all bifurcate; (3) that the 

 3rd longitudinal vein is short, and commonly takes off from 

 the second at such an angle that its origin is sometimes 

 spoken of as a " supernumerary cross-vein " ; (4) that there is 

 no true posterior cross-vein (though the anterior basal cross- 

 vein is sometimes wrongly called by that name), and no 

 posterior basal cross-vein ; and (5) that all the veins are clad 

 with scales, except in the small subfamily CorethrincB, where 

 hairs take the place of scales. These scales, as a rule, are of 

 two kinds, namely, short, broadish, " median " scales that cling 

 to the vein, and longer and narrower "lateral" scales that 

 stand out on either side of it. Another wing-feature that must 

 be noticed is that besides the ordinary longitudinal veins there 

 are generally two longitudinal creases or false veins : one of 

 these looks like a continuation of the 3rd longitudinal vein ; 

 the other looks like a 7th longitudinal vein. This last in one 

 or two species only, bears a few scales. 



The halteres are plainly visible, there being no squames 

 to conceal them. 



The legs, which are clad with scales, are long and slender, 

 the 1st tarsal segment (which is sometimes, by a sort of 

 metaphorical inversion, spoken of as the " metatarsus," as if 

 the metatarsus of the vertebrate skeleton were the proximal 

 element of the sole of the foot instead of being the distal 

 element) contributing a very considerable part of their length. 

 The 5th tarsal segment carries a pair of claws, which in the 

 male may be serrated. 



The main features of the alimentary system are shown 

 in Fig. 8. 



The male differs from the female most conspicuously in 

 the form of the antennae. 



The eggs of Culicidae are laid on the surface of water 

 either in a sheet of jelly something like diminutive frog- 



