IOO 
Parasitic Arthropoda 
mouth-parts, legs, and wings of the future adult are now external, but 
enclosed in chitinous cases. On the upper surface, near the base of 
the wings are two trumpets, or breathing tubes, for the pupal spiracles 
are towards the anterior end instead of at the caudal end, as in the 
larva. At the tip of the abdomen is a pair of large chitinous swim¬ 
ming paddles. 
As illustrative of the life cycle of a mosquito we shall discuss the 
development of a common house mosquito, Culex pipiens, often 
referred to in the Northern United States as the rain barrel mosquito. 
Its life cycle is often given as typical for the entire group, but, as we 
have already emphasized, no one species can serve this purpose. 
The adults of Culex pipiens hibernate throughout the winter in 
cellars, buildings, hollow trees, or similar dark shelters. Early in 
the spring they emerge and deposit their eggs in a raft-like mass. 
The number of eggs in a single mass is in the neighborhood of two 
hundred, recorded counts varying considerably. A single female 
may deposit several masses during her life time. The duration of 
the egg stage is dependent upon temperature. In the warm summer 
time the larvae may emerge within a day. The larvae undergo four 
molts and under optimum conditions may transform into pups in 
about a week’s time. Under the same favorable conditions, the pupal 
stage may be completed in a day’s time. The total life cycle of Culex 
pipiens, under optimum conditions, may thus be completed in a week 
to ten days. This period may be considerably extended under less 
favorable conditions of temperature and food supply. 
Culex pipiens breeds continuously throughout the summer, 
developing in rain barrels, horse troughs, tin cans, or indeed, in any 
standing water about houses, which lasts for a week or more. The 
catch basins of sewers furnish an abundant supply of the pests under 
some conditions. Such places, the tin gutters on residences, and all 
possible breeding places must be considered in attempts to extermi¬ 
nate this species. 
Other species of mosquitoes may exhibit radical departures from 
Culex pipiens in life-history and habits. To control them it is essen¬ 
tial that the biological details be thoroughly worked out for, as 
Howard, Dyar, and Knab have emphasized, “much useless labor and 
expense can be avoided by an accurate knowledge of the habits of the 
species.” For a critical discussion of the known facts the reader is 
referred to their monograph. We shall confine ourselves to a few 
illustrations. 
