June, 1929] MOSQUITOES OF NEW HAMPSHIRE 11 



covered by water, because they must be frozen before hatching can take 

 place. The adult females may live for two months or more. 



A variation of this type of life histoiy occurs in a few species where 

 all the overwintering eggs do not hatch when first covered with water, 

 but some hatch each time the pools are filled by rains during the sum- 

 mer. In these species there appear to be several generations, when in 

 fact there is onlj- one. 



Some mosquitoes, particularly the salt-marsh mosquitoes, winter in the 

 egg stage, but have several generations each j'ear. The eggs are laid on 

 sod or mud in depressions, and the number of generations depends on 

 the weather; that is, the eggs hatch whenever the depressions are filled 

 by heavy rains or extra high tides. 



A number of oiu- species {Culex, Anopheles, Uranotcenia) pass the win- 

 ter as fertilized, adult females. The eggs are laid directly on the surface 

 of the water. In these mosquitoes breeding is continuous, one genera- 

 tion following another throughout the summer. 



Three New Hamj^shire mosquitoes pass the winter as larvse (Mansonia, 

 Wyeoniyia and Culicella melanura) . The eggs are laid on the surface 

 of the water. The first has but one generation, the last two have more 

 than one generation each ye&v. 



NATURAL CONTROL 



Climate, particularly temperature and rainfall, plays an important 

 part in determining the abundance of mosquitoes. It is often the most 

 important factor in the natural control of mosquitoes breeding in temp- 

 orary pools and puddles. Low temperatures retard the growth and de- 

 velopment of all immature stages, and if there is not abundant moisture 

 the pools may dry up before the adults emerge. High temperatures with 

 little or no rainfall, which drj- up pools verj' rapidly, maj' kill the mos- 

 quitoes before the\' have completed their development, or may prevent 

 fm-iher breeding through lack of suitable pools. During such seasons 

 the total number of mosquitoes will be much reduced. On the other 

 hand, seasons with normal or high temperatures and abundant and fre- 

 quent rainfall will result in great numbers of mosquitoes, for the max- 

 imum number of breeding places will be a\'ailable. Such unusual sea- 

 sons may even permit some breeding in drained or ditched areas. 



Many animals are known to feed on mosquitoes, some having no other 

 food. These natural enemies are verj"- seldom able to control the pests 

 completely because of the short life history of mosquitoes, the varied 

 and specialized breeding places, and the high rate of reproduction. Thej^ 

 do, however, materially reduce the numbers of mosquitoes and under 

 certain conditions may constitute an efficient control. 



Bats will eat mosquitoes but they prefer larger insects. Certain birds 

 are known to feed on them occasionallj'. The nighthawk, the whip-poor- 

 will, the swallows, and the flj^catchei-s somestimes catch the adults, while 

 some shorebirds and wading birds, as sandpipers and phalaropes, eat the 

 larvae and pupae. The principal natural enemies live in the water and 



