Culicidce, or Mosquitoes 



99 



CLnt&nnaL 



female. The most characteristic feature is that the margins of the 

 wings and, in most cases, the wing veins possess a fringe of scale-like 

 hairs. These may also cover in part, or entirely, the head, thorax, 

 abdomen and legs. The females, only, suck blood. 



On account of the importance of the group in this country and the 

 desirability of the student being able to determine material in various 

 stages, we show in the accompanying figures the characters most 

 used in classification. 



The larvae (fig. 73) are elongate, 

 with the head and thorax sharply 

 distinct. The larval antennae are 

 prominent, consisting of a single 

 cylindrical and sometimes curved 

 segment. The outer third is often 

 narrower and bears at its base a 

 fan-shaped tuft of hairs, the ar- 

 rangement and abundance of which 

 is of systematic importance. About 

 the mouth are the so-called rotary 

 mouth brushes, dense masses of 

 long hairs borne by the labrum 

 and having the function of sweep- 

 ing food into the mouth. The 

 form and arrangement of thoracic, 

 abdominal, and anal tufts of hair 

 vary in different species and present 

 characteristics of value. On either 

 side of the eighth abdominal seg- 

 ment is a patch of scales varying 

 greatly in arrangement and number and of much value in separating 

 species. Respiration is by means of tracheae which open at the apex 

 of the so-called anal siphon, when it is present. In addition, there 

 are also one or two pairs of tracheal gills which vary much in appear- 

 ance in different species. On the ventral side of the anal siphon is a 

 double row of flattened, toothed spines whose number and shape are 

 likewise of some value in separating species. They constitute the 

 comb or pecten. 



The pupa (fig. i3Q,b) unlike that of most insects, is active, though it 

 takes no food. The head and thorax are not distinctly separated, but 

 the slender flexible abdomen in sharply marked off. The antennae, 



Culex larva showing details of external 

 structure. 



