i4 Mosquitoes 



This labium is of heavy chitin and is toothed, the 

 number of teeth being constant (within a variation of 

 at most two teeth) for many species, but widely vari- 

 able in a few. A fuller discussion of the mouth-parts 

 will be given in the section relating to larval habits. 



On the back of the head, at the roots of the an- 

 tennae, are, except in the genera Anopheles, PsoropJi- 

 ora and Megarhinns, bunches of hairs, usually eight 

 or ten hairs in each group. Nearer the centre of 

 the head are four tufts, generally with from one to 

 about eight hairs, and, in the great majority of spe- 

 cies, the number of hairs in these tufts is constant in 

 at least the last stage of the larvae, and forms a good 

 specific character. In one genus {Uranotcznia), 

 these tufts are represented by four spines. The tuft 

 at the base of the antennae, the antennal tuft, when 

 having more than three or four hairs, and often the 

 other two sets of tufts, are finely plumose, evidently 

 sensory. There is a short bunch near the eye, and 

 often one or two more, of from one to three hairs, 

 on the head. 



The thorax is not so heavily chitinised as the head. 

 In reality it consists of three segments, but these are 

 not easily recognised from the contour. They are 

 marked, however, by three rows of long hairs, 

 which extend, one across the anterior margin of the 

 thorax, one a little in front of the middle, and one 

 some distance from the posterior margin. Some of 

 these hairs are single, some form tufts. All arise 

 from more or less conspicuous tubercles, more 

 strongly chitinised than the rest of the thorax. The 

 large tufts are decidedly plumose (very short plun> 



