INFLUENCE OF ENVIRONMENT 



TEMPERATURE 



TEMPERATURK, as shown in the preceding chapter, probably affects 

 mosquito life more widely than anything else. The mosquito is a 

 cold blooded animal and its body temperature is usually only a few de- 

 grees higher than the temperature of the surrounding medium. The 

 temperature of the medium surrounding the insect determines the rate 

 of its metabolism, may destroy it by freezing or may kill it by heating. 



Field observations of the behavior of Aedes sollicitans and Aedes 

 cantator adults, as reported by Rudolfs in Bulletin 388, A'^. J. Agri- 

 cultural Ex'periment Station, showed that a temperature between 68°F. 

 and 77 °F. had the greatest accelerating influence upon the rate of their 

 activities. The author has observed that adult activity is very slight 

 when the temperature falls to 60°F. and virtually ceases at 40°F. 

 Death follows formation of ice within the body, but does not occur 

 above 30°F. and usually only at lower temperatures. 



Experiments conducted by the author in 1940 and 1941 with larvae 

 of Culex pipiens and Aedes aegypti showed that metabolic activity of 

 the larvae was greatest between 68°F. and 87 °F. As temperatures rose 

 above 90°F., activity slowed down. Death occurred within a few days 

 at temperatures of 102 °F. and over. 



Mosquito species passing the winter as adults in the latitude and ele- 

 vation of New Jersey are nearly always so reduced in numbers that they 

 cannot reach large numbers before midsummer. Mosquito species pass- 

 ing the winter as eggs can and usually do produce large broods prior to 

 midsummer. As study of the 1933 trap collections will show, Culex 

 pipiens, which passes the winter as an adult, is the dominant species, but 

 these records show that this position of dominance is not reached until 

 July. On the other hand Aedes canadensis and Aedes vexans, both of 

 which pass the winter as an egg, are abundant prior to July. Once each 

 year, during the winter, the mosquito fauna is greatly reduced in num- 

 ber by low temperature and must make a new start the following spring. 



Larval development during the spring is so slow that a species re- 

 quiring seven to eight days in midsummer will not complete its larval 



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