bacot: mosquitoes and the danger of malaria. 243 
to man than any other group. To this order belong such proved 
carriers and distributors of disease-germs as the House and Blow¬ 
flies ; also the numerous biting species—Tabanids, Stable flies, 
Tsetse flies, Blood-sucking midges, etc. The mosquitoes form, 
from man’s point of view, the crowning infamy of the Diptera. 
The actual theft of blood from their victims is a very minor 
matter, compared with the irritation caused by the injection 
of their saliva into the wound ; while in the background lurks 
the danger of inoculation with some disease-germ introduced 
during the process of feeding. Agriculturists, again, have to 
deplore the inroads made by dipterous larvae on growing crops. 
It is true that some of the two-winged flies are Ishmaels and 
destroy their relatives, but it is doubtful if these species com¬ 
pensate for a tithe of the harm wrought by their fellows. 
Like all the groups of insects belonging to the order Diptera, 
the mosquitoes undergo a complete metamorphosis during the 
period of development from egg to adult, the larvae hatching 
from the eggs being entirely different in form and habit from 
their parents. 
The Eggs .—Female mosquitoes usually lay their eggs on 
the water-surface or the wet margins of a pool, occasionally 
on wet mud. The instincts of certain northern species lead 
them to deposit their eggs in the bottom of dry hollows, which 
are converted into pools only in the following spring by the 
melting of the winter snow; but no English mosquitoes are 
known to have this habit. 
The eggs may be deposited singly or attached together in the 
form of rafts, which float upon the surface of the water, head end 
downwards, according to the species laying them. Those laid 
singly on water may either sink, float, or become stranded on 
the margins of the pool ; and, in accordance with their specific 
nature, individual constitution, or treatment, they may either 
hatch promptly or the larvae may defer emergence from the 
shell for a long period after incubation. It seems, however, 
a constant rule that eggs of the species which cement them 
together to form a raft must hatch promptly or perish. 
The Larva, though adapted for an aquatic life only, may 
survive in some cases for several days in wet mud, but are 
unable to complete their development in the absence of sufficient 
water to swim in. In feeding, they seem to rely chiefly upon 
