258 GNATS OR MOSQUITOES — CHAPTER X 



reference, though manj' of the figures are, as a matter of 

 fact, reahstic. The figures placed in the middle line of the 

 figure are all those of the type genus of the family Culex, 

 and on either side are placed figures of the structures of 

 such genera as diverge from the type genus ; it being 

 understood that in each instance, the corresponding regions 

 of genera not figured conform more or less to the Culex type. 

 For example, the clypeus is nude in all Mosquitoes except 

 those belonging to the genera Stegomyia, JEdomyia, and 

 Trichoprosopon, in the two former of which it is scaly, those 

 of the first genus being provided with a pair of tufts of 

 scales of a peculiar sigmoid form ; while in the latter, it is 

 clothed with a rather dense brush of hairs. 



Commencing at the top of the illustration, the figures 

 arranged in the first two lines will be found to refer to the 

 arrangement of the scales of the nape. In this region, the 

 clothing scales will be found to belong generally to one of 

 three types, namely, (a) fiat, spade-shaped scales, arranged 

 overlapping each other in regular order, like the tiles of a 

 roof, so as to form a smooth imbricated armour, which usually 

 displays to the best advantage the pecuhar " metallic " inter- 

 ference tints exhibited by scales of this sort when illuminated 

 at certain angles ; or (6) narrow curved scales, such as those 

 shown in fig. 16/, which always give a characteristically 

 woolly appearance to parts clothed by them, and owe such 

 tints as they may possess to their natural coloration, inde- 

 pendent of the point of view ; and (c) upright forked scales, 

 narrow, stiff, bifid structures, usually black, which bristle 

 out usually at an opposite angle to that taken by the 

 associated scales of the other two types. In all Mosquitoes 

 the sides of the head are covered with a pavement of scales 

 of the first-mentioned sort, but in all except those of the 

 Megarhiiiina sub-family and in Toxorhynchites, in which 

 they uniformly cover the whole of the back of the head,, 

 they are associated with one or both of the other types 

 of scale. In the type-genus Culex the flat scales are con- 

 fined to narrow patches, quite away at the sides, while 

 the whole of the middle portion is covered with narrow 

 curved scales, which constitute the entire tomentuni on 



