L 
hry. 9 
DIPTERA. 27 
Eggs are deposited in small boat-shaped masses and the larvee hatch- 
ing from these escape into the water. They move about by a jerky 
motion, often ascending to the surface to obtain a fresh supply of air 
which is taken through a slender tube at the caudal end (fig. 2). The 
pup are also active and move about in the water during their brief 
existence in this form, rising to the surface for air, which is taken 
through a spiracle near the head When the insect is ready to emerge 
the pupa rests at the surface with the dorsal face slightly out of the 
water, the case splits and the mosquito draws out first the front legs 
Fia. 2.—Culex pungens: larva at left, pupa at right, with anal segment below—all enlarged (from 
Howard). 
which are placed on the water to serve as support while the rest of the 
body is withdrawn. The wings expand very quickly and the insect 
flies away. 
About one hundred and fifty species of this family have been 
described, and of these over thirty belong to North America. They 
are mostly divided among the genera Culex, Anopheles, and Corethra, 
the majority, however, twenty-seven accredited species, being included 
in the genus Culex. These may be considered as mosquitoes proper, 
and all our most annoying forms. 
