Noctttrnal habits. 



occurred in our own experience in which " anopheles " flew about 

 and even attempted to feed in broad daylight, but, as a rule, they are 

 strictly nocturnal in their habits. This fact was long ago brought 

 forward by one of us in support of the view that in many parts 

 of India these mosquitoes act as the usual intermediate hosts of 

 Filaria nocturna, the embryos of which, as is well known, are 

 present in the peripheral blood only at night. The readiness with 

 which " anopheles " can be killed by placing the bottle containing 

 them for a short time in bright sunlight, the fact that they are 

 found during the daytime only in the darkest corners of rooms, 

 that they seldom or never rest upon light-coloured clothes or on 

 cleanly whitewashed walls, and the fact that whereas " culex" mos- 

 quitoes emerge from the pupa case at any time of the day or night, 

 "anopheles " very rarely emerge until evening, all point to the 

 conclusion that these insects are essentially nocturnal in habits. 



THEIR LENGTH OF LIFE. 



The usual length of life of adult " anopheles " is not known with 

 any exactness, but it is certainly considerable. Although the habit 

 of hibernation has not been observed in any of the Indian species, 

 Annett and Button have described it in the English species A, 

 maculipennis, which must therefore be capable of living at least 

 some months. It is also well known that adult " anopheles " can sur- 

 vive throughout the whole of the hot weather in India and Africa, 

 even when all breeding places are dried up. According to Stephens 

 and Christophers the adults remain during this time in the houses, 

 and though they feed regularly, they do not lay eggs, even when 

 artificial breeding places are made. One of us has also recorded 

 the fact that " anopheles " caught in houses at Ellichpur, in the 

 Berars, between March and June did not lay eggs, though they 

 readily did so at other times of the year. Stephens and Christo- 

 phers describe the habit of remaining in houses during the hot 

 weather under the term " a3stivation." Adult "anopheles" may, 

 with care, be kept alive in captivity for two months or more. 



THE " SWARMING " OF ANOPHELES. 



In his account of the anti-malarial operations at Mian Mir, 

 Dr. Christophers describes, under the heading of " The Swarming 

 of Anopheles," a habit which had not previously been noted with 



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