MOSQUITOES AND FLEAS. 



15 



The length of time which elapses for a generation, which we have 

 just mentioned, is almost indefinitely enlarged if the weather be oooL 

 As a matter of fact, a long spell of cool weather followed the issuing of 

 the adults just mentioned. Larvae were watched for twenty days, dur- 

 ing which time they did not reach full growth. 



The extreme shortness of this June generation is significant. It 

 accounts for the fact that swarms of mosquitoes may develop upon 

 occasion in surface pools of rain water, which may dry up entirely in 



Fig. l.—Culexpungens: Full-grown larva at left; pupa at right above, its anal segment betow- 



greatly enlarged (original). 



-all 



the course of two weeks, or in a chance bucket of water left undis- 

 turbed for that length of time. Further, the shortness of this genera- 

 tion was, while not unexpected, not at all in accordance with any pub- 

 lished statements as to the length of life of any immature mosquito of 

 any species. But these published statements, as previously shown, 

 were nearly all based upon observations made in a colder climate and 

 in the month of May. 



On August 1 Mr. F. C. Pratt, an assistant in the division o( onto- 



