66 PROCEEDINGS ENTOMOLOGICAL SOCIETY 



this is what we should expect, for they are short-lived and 

 need little nourishment. The prevalent idea, that mosquitoes 

 are primarily blood-suckers, is erroneous and due to the fact that 

 the blood-sucking species have forced themselves upon man's 

 attention; this has led to the assumption that the entire group 

 are blood-suckers. Most likely less than half of the existing 

 species are blood-suckers, and the habit in these is developed 

 in varying degrees. There are species which bite but rarely 

 and show little aggressiveness. But in others the desire for 

 blood is the supreme passion and for some of these a blood - 

 meal is absolutely necessary for the preservation of the spe- 

 cies; the female must have it to develop her ova. Not only 

 this, but in one species, the yellow-fever mosquito (Acdes ca- 

 fapits}, we find the extreme of development in this direction, 

 an adaptation to a single vertebrate, man. So closely is this 

 mosquito associated with its host that it cannot exist apart 

 from him, and it has been shown that the eggs of this species 

 will not develop properly unless the female has fed on human 

 blood. 



Mr. Hall argued that the existence of the life-cycle of the 

 malarial organism, with its alternate hosts of mosquito and 

 man, indicated that the blood-sucking habit of mosquitoes 

 must be very ancient, as this must have existed before the ma- 

 larial organism, as such, could be developed. 



Dr. Gill replied that in a geological sense the blood-sucking 

 habit of mosquitoes could be looked upon as recent, just as the 

 human species must be considered of very recent origin. 

 Moreover, cases are known where a new habit was acquired 

 by an animal very quickly. He mentioned several instances 

 of great perversions of habit being quickly acquired by ani- 

 mals, due to a new element being injected into a fauna, among 

 them the flesh-feeding habit of the kea of New Zealand, which 

 was acquired only after the introduction of sheep into that 

 country. However, in such instances as the mosquitoes which 

 carry malaria the delicate correlation indicates that the habit 

 is one of long standing. 



Dr. Gill said that in the study of this problem, of the ac- 



