60 Journal New York Entomological Society. [Volxxt. 



species of Anopheles, and those of which the eggs sink and remain at 

 the bottom unhatched for almost a year as in Culex suhcantans, pre- 

 tans, ahserratus, etc. The former division, which continues to breed 

 throughout the summer, usually selects the more permanent open 

 swamps; the latter division selects woodland pools which last only 

 during the spring months. 



Vegetation in the water has much effect upon the mosquito life 

 in it. Thus except in the most temporary rain pools mosquito larvae 

 and pupae in water free from plants would be exposed to the attacks 

 of many enemies and so be unable to maintain themselves. Vegeta- 

 tion serves as a protection to the eggs, the larvae and the pupae. On 

 the other hand, if the vegetation is too dense it precludes the possi- 

 bility of the larvae gaining access to the surface (and most of them 

 must do this, as had been said) and so literally drowns them; Spiro- 

 gyra, the green scum found so commonly in stagnant water of a more 

 permanent character, acts in much the same manner as the ordinary 

 surface vegetation, but in addition to shutting off the air supply fre- 

 quently entangles the larvae and drowns them before they reach a 

 point even near the surface. In the larger woodland pools where 

 water beetles are abundant the larvae naturally keep to the edges and 

 cautiously move along the bottom under the protection of the sunken 

 leaves. 



Temperature likewise has considerable effect on the larvae and 

 pupae, but scarcely as to influence choice of environment. In early 

 spring these stages may together extend over a period of six weeks, 

 while in midsummer the same species may pass from egg to adult in 

 ten days. On the other hand a low temperature seems to have little 

 effect on the hatching of the eggs. Some of the spring species may 

 emerge from the tgg in February, and an tgg boat of pipiens will 

 produce young as quickly when placed in spring water as when placed 

 in rain water. Agitation seems to be of greater consequence than 

 temperature in the hatching of the eggs. A rainstorm therefore will 

 often hasten the eggs to hatch. 



As to the distribution of mosquitoes all the species appear to be 

 found wherever their respective environments occur. Thus while 

 such species as Culex abfitchii, canadensis, frtusica and pretans are 

 common in the wooded districts of the north of New Jersey they are 

 also found in these same districts in the south of this state — in lesser 



