HIBERNATION OF ANOPHELES 259 



up to the onset of the monsoon, after which it becomes exceedingly 

 numerous. A.fiiliginosus, on the other hand, is distinctly the cold weather 

 species in the Punjab, and continues to lay its eggs throughout the 

 winter ; like c ul id fades, it diminishes in numbers with the advance of 

 the hot weather, but it does not increase in the same way immediately 

 after the rains, the numbers- remaining comparatively small until long 

 after culicifacies is well established. A. rossii disappears entirely in the 

 colder months, and does not reappear till the middle of July. The 

 determining factor is probably the optimum temperature for the deve- 

 lopment of the larva of each species. 



It should be noted that the nature, as distinct from the amount, of the 

 rainfall is important in relation to the prevalence of mosquitoes after the 

 rainy season. Continuous torrential rain tends both to wash away the 

 larvae and to prevent the females from successfully depositing their eggs. 



Mosquitoes, like all insects which normally have a short life history 

 and which can multiply only under certain conditions, are able to exist, 



by one means or another, during unfavourable seasons, 



1.1,1 , . j ~, u Hibernation and 



in order that the race may be carried on. The com- 



... , , Astivation 



monest manner in which this is brought about is by the 



hibernation of impregnated females, which, finding the season too far ad- 

 vanced to complete the maturation and deposition of their ova, seek out 

 resting places and remain concealed until favourable conditions present 

 themselves at the commencement of the next season. During this period, 

 which may extend to many months in temperate climates such as that of 

 Europe, they feed seldom if at all, and remain in a passive and torpid 

 condition, living upon the store of food material already accumulated, 

 until they are revived by the warm weather. The eggs are then laid, and 

 it is from these first batches of eggs that the mosquitoes of the ensuing 

 season are produced. 



Annett and Dutton, in the course of their observations on the hiber- 

 nation of English mosquitoes, record having found a number of females 

 of A. maculipennls in cellars, lumber rooms, wash houses and similar 

 localities in the month of February. In all these situations the anophe- 

 lines were resting in a culex-like attitude ; they were difficult to rouse, 

 and when caught in a bottle crawled rather than flew into it. They 

 never found any of the mosquitoes in stables and cattle sheds, as these 

 places were comparatively dry and were constantly warmed by the 

 animals-at night. Not a single male maculipennls was seen throughout 

 the observations, which extended over several months in the winter ; this 

 fact indicates that it is the female alone which hibernates. 



