HIBERNATION 119 



upon Aedes spencerii, under iiuusually favorable conditions, indicate a length of 

 life of from two to three weeks for the males of that species. Indications are that 

 only a very few of the males live to the maximum of three weeks. It was possible 

 to gauge the length of life of these males thus accurately because this species has 

 but a single brood and all the adults issued within, at the most, a week. 



The length of life of the female exceeds that of the male but differs with the 

 species and with circumstances. In temperate regions certain species hibernate 

 and these probably live longest as their activities are divided by an intervening 

 long period of quiescence. In these cases the length of the winter will determine 

 the longevity of the mosquito and we must look upon certain species of Culiseta 

 and Anopheles which occur far to the north as living longest. 



There is a correlation between the habits of oviposition and length of life. 

 Members of the genera Culex, Culiseta, Lutzia and Uranotcenm deposit all their 

 eggs at one time in a mass and death ensues immediately or soon after the eggs 

 are laid. The females of these genera may be said to be short-lived, the species 

 being perpetuated through a rapid succession of broods during the warm months. 

 In Aedcs, where the eggs are deposited in small lots, at intervals, the female 

 lives much longer, in many cases several months. Accurate data can not often 

 be had on account of disturbing factors and we must rely largely upon our 

 general knoAvledge of the species. In a few cases, however, we have experimental 

 or other evidence which is conclusive. Aedes calopus has been a frequent subject 

 of experiment and females have been kept in captivity as long as 154 days, al- 

 though this appears to be far in excess of the normal span of life. Observations 

 by Knab, made in western Massachusetts in 1903, indicate that the females of 

 certain species of Aedes live at least three months. He found that Aedes stimu- 

 lans, A. fltchii and A. ahfitchii have but a single brood which develops early in 

 the spring. The data for the three species coincide so closely that they may be 

 considered together. The earliest capture (as appears from preserved speci- 

 mens) of a female was April 29; they continued abundant and troublesome 

 through May and June but showed some decrease during August. We have 

 specimens captured as late as September 12. 



HIBERNATION AND /ESTIVATION. 



With the majority of the species of mosquitoes the unfavorable season is 

 passed in the egg state. Certain genera, however, pass the winter, and in cer- 

 tain tropical regions the dry season, in the adult state. In such cases it is only 

 the female that survives, having been previously fertilized, to deposit her eggs 

 at the beginning of another season. Theobald states that the male of Culiseta 

 annulatus hibernates in England but this record stands quite alone. It is certain 

 that at least in the genera Culex and Anopheles no males survive the winter. 

 The hibernating females seek shelter with the approach of cold weather and at 

 this time they show no inclination to feed. Those species more or less associated 

 Avith man take advantage of the shelter of cellars, stables, sheds and other build- 

 ings, the darkest ones apparently being the most favored. They have also been 

 found hibernating in caves. Other species retire to hollows in trees, crevices in 



