REPORT ON MOSQUITOES. 23 



does not feed, no poisons that act through the ahmentary canal, 

 either directly or indirectly, affect it, hence some materials that 

 act satisfactorily on the larva are ineffective as against the pupa ; 

 a point which will be further touched upon in another place. 



The pupal stage is short, as a rule, lasting less than a day in 

 some cases in mid-summer wlien droughty conditions prevail. 

 Usually two to four days may be considered normal, but in cool 

 weather a week or even two weeks is not unusual. 



There is little difference between pupae within generic limits^ — 

 at all events nothing that can be readily observed; hence prac- 

 tically no attention is paid to this stage in the descriptive work. 

 Only types of each marked variation are figured. 



VVhen the adult is fully developed within the pupa the latter 

 becomes less active ; it loses its curved position and tends to 

 straighten out; finally the skin bursts along the middle of the 

 back, and the adult rises up almost vertically without apparent 

 effort, seeming really to ooze out of the envelope until the wings 

 are free. Then the long legs are carefully withdrawn and the 

 mosquito rests, fully developed but very soft and moist, on a 

 boat formed of the pupal shell. In a few minutes the drying 

 process is completed and the insect flies away. 



THE MOSQUITO WING. 



The wings of mosquitoes are long and narrow, fringed with 

 characteristic scales, the veins are set with scales of two or three 

 kinds along their course and, in the spotted winged forms, the 

 marks are usually produced by dark colored, massed scales. This 

 is one of the characteristics of the mosquito family, for very few, 

 comparatively, of the flies have scaly wings. 



On the upper surface the scales are usualy of a pointed, feather 

 shape, on the under side they are more usually truncated. They 

 are arranged along the veins in a feathered series, all pointing to 

 the edge of the wing. Under the microscope the transparent sur- 

 face of the wing is seen to be set with small spinous processes, 

 which, by interfering with the light rays, give rise to the iridescent 

 appearance. 



The venation or arrangement and course of the veins is con- 

 stant throughout the family, though there is some variation in 

 the length of the forks. The form of the wing scales varies suf- 

 ficiently to make them of some importance in classification; but 

 that point will be more fully referred to in the systematic portion 

 of this work. 



