2 MOSQUITOES 



from the top of the thorax. The thorax of all is much 

 swollen, aud with all pupa) the bodies seem lighter than 

 air, so that they float at the surface without exertion. The 

 pupc^, however, are active — sometimes very active. The 

 abdomen, with anal oar-like flaps, may be quickly and 

 violently agitated so as to draw them down below the 

 surface, when it becomes necessary to escape from a fish 

 or from some predatory aquatic insect. This great activity 

 is necessary for the preservation of species, since stagnant 

 j)ools abound with carnivorous forms of life, and such a 

 little, fat morsel as a mosquito pupa, if it always stayed 

 quietly at the surface, would stand no chance. When 

 one tries to catch a pupa with his thumb and forefinger, 

 at even the approach of the hand it disappears like a 

 flash, rising slowly to the surface again when the active 

 movements of the abdomen cease ; that is to say, when 

 it gets tired or when danger ceases to threaten. 



All mosquitoes, so far as known, are rather rapid 

 breeders. They pass through several generations in the 

 course of a year, and hibernate in both adult and larval 

 stages. Over-wintering mosquitoes ma}^ frequently be 

 found in the cellars of houses, in cold garrets, in barns, 

 under the lids of water-tanks, under bridges and stone 

 culverts. In the extreme Southern States many mosqui- 

 toes are active all through the winter, and in most tropi- 

 cal regions they may breed all the year round. In dry, 

 tropical regions, however, they breed only through the 

 rainy season, and in the dry spell the species is iierpetu- 

 ated by the persistence of the adults, which either remain 

 active, or more usually rather inactive or dormant, just 



