their Relation to Disease. 
7 
end. Although the larvae of the different species of mosquitoes 
vary considerably in the frequency with which they come up to 
breathe, there is none that can live for more than a few hours 
when deprived of access to the air. 
The larval period is one of growth, during which the skin is 
cast three times. At the end of this time—which may vary in 
length from a few days to several weeks, according to the condi¬ 
tions of temperature—growth is complete, and the larva casts its 
skin a fourth time to become a pupa. The pupa is a very different 
looking object from the larva; instead of being elongate and more 
or less cylindrical, it is of a form which has very aptly been 
Fig. 2.—Larvae op Mosquitoes. 
(a) Anopheles inaeulipennis, Mg.; (b) Stegomyia fasciata, F.; (c) Culex fatigmu\ 
Wied. X 4. 
described as “ comma-shaped,” consisting of a very large “head ” 
with a “tail” attached; at the end of the “tail” are a pair of 
“ paddles,” which assist the pupa in its extremely active move¬ 
ments through the water. The pupa takes no food, but like 
the larva it breathes air from the surface of the water; its 
breathing organs, however, instead of being situated at the tail 
end are placed close to the head. 
At the end of a few days (from one to five) the pupa comes 
to rest at the surface of the water, the skin splits along the 
back and the mosquito emerges. 
Such, in outline, is the general life-history of all mosquitoes; 
but, as might naturally be expected, there is a great deal of 
variation in detail both in the structure and the habits of these 
