236 Transactions . — Miscellaneous. 



venting infection of man by the mosquito there are also 

 two courses open — to destroy the mosquitos or protect the 

 man. The possibility of the latter, the protection of the 

 man, we have already shown. The destruction of the mos- 

 quito is a very big order, but when its life-history and habits 

 are studied it is seen to be possible within limitations. 



Let us for a moment consider the life-history of the mos- 

 quito. The great interest aroused by Ross's discovery has 

 made our knowledge of the subject much greater and more 

 exact. Different species have different habits, but there is 

 a great deal common to all. The members of the family 

 Culecidce, to which both Cidcx (the common gnat) and Ano- 

 pheles belong, pass, like other insects, through different stages 

 of existence, presenting in these stages very different appear- 

 ances and very different modes of life. From the eggs are 

 batched the larvae. These inhabit pools of water or the 

 quiet edge of a slowly flowing stream. They feed on minute 

 organisms growing in the water, on vegetable matter, also on 

 each other and on the larvae of other insects. They require 

 air, and come to the surface to breathe. After a time the 

 larva sheds its outer coat and becomes the pupa, which also 

 lives in the water, but which, unless disturbed, rests quietly 

 at the surface. If disturbed it jerks itself rapidly and forcibly 

 to the bottom. After two or three days the pupa in its turu 

 breaks open its outer skin and the adult mosquito emerges. 

 Hitherto the insect has been aquatic in its habits ; but the 

 mosquito, after resting on the pupal skin through which it has 

 brokeu until its wings are hardened, flies off to the nearest 

 shelter, seeking in the day-time a retired dark spot, but 

 issuing forth at night in search of food. Within a few 

 minutes of sundown it goes abroad, and punctually just 

 before sunrise seeks its hiding-place. (Hence the reason 

 that malaria is contracted mostly at night, and an explana- 

 tion of the fact that exposure to night air has been for ages 

 regarded as a potent factor in the causation of malaria.) 

 The mosquito feeds on various foods, sucking readily the 

 juices of plants and fruits. It is only the females which are 

 blood-suckers ; the male is a vegetable feeder. As a result 

 of observation and experiment, it is believed that the 

 sucking of blood by the female is connected in some way 

 with the proper development of her eggs. Only those 

 mosquitos which have sucked blood produce fertile eggs. 

 After gorging itself the female returns to cover. She does 

 not fly far, and is not carried by the wind, for when the wind 

 is strong the mosquito rests quietly. This fact explains why 

 malaria is contracted often within a very limited area of a dis- 

 trict or village. The mosquito does not travel beyond the 

 immediate vicinity of its birthplace. Nor does it fly high in 



