246 BACOT : MOSQUITOES AND THE DANGER OF MALARIA. 
so that the perfect mosquito emerges into the air from the pupa : 
case, which serves as a raft to support it during the process of 
ecdysis. 
So far as exact knowledge extends, female mosquitoes require 
a meal or meals of blood before they can develop their ovaries. 
In a few cases, out of a large number of experiments, eggs have 
been laid by females fed on syrup and other foods ; but the 
number of successes compared with the number of failures 
suggests that the former are exceptions which tend to confirm 
the rule. It has been suggested, because mosquitoes are known 
to swarm in Arctic wastes where they can hope to obtain blood 
at rare intervals only, that they must be able to produce eggs 
on some diet other than blood ; but the argument is not conclu- 
'sive. The facts are capable of explanation on other assump¬ 
tions—as, for instance, that some of the eggs of each batch 
laid may remain dormant for long periods before hatching. 
Male mosquitoes do not suck blood. The few recorded 
exceptions of this rule are thought by Edwards to be due, possibly, 
to the action of females with male secondary sexual characters. 
The males are known to feed on syrup ; also to visit flowers 
and decaying organic matter. Further, they will at times 
insert their probosces into the skin pores, probably to suck up 
perspiration. 
The blood required by the females need not necessarily 
be human. It is probable that a few only of the many species 
habitually attack man (Edwards estimates that there are 
upwards of 1,000 species, only 18 of which occur in Britaiq). 
What seems certain, however, is that the species which do 
suck man’s blood exist in innumerable numbers ; so that possibly 
it would be correct to state that the greater proportion of these 
two-winged fiends are inimical to man. It is probable, however, 
that man is not really the normal host of a large number of 
species which habitually attack him when opportunity occurs ; 
and it is, at the same time, certainly true that many of the 
species closely associated with man will feed on the blood of 
other animals when pressed for food. 
Mosquitoes are very prolific insects. Some Anopheles 
mosquitoes are stated to lay as many as 1,500 eggs. I have 
known the species associated with yellow fever to lay upwards 
of 1,000. The raft-making species are stated to lay from 120 
