
AQUATIC INSECTS OF FRESHWATER 

together, which float about 
five or six days till the em- 
brios emerge from the under 
side and at once take to the 
water. The larve keep near 
the sides of the pools or just 
below the water level, as 
they are not deepwater 
feeders and must fre- 
quently come to the sur- 
face to breathe, the oriface 
of the air tube being thrust 
out of the water. After a 
number of molts the pupa 
is developed, which has the 
head, thorax, wings and legs 
folded in one mass and the 
abdomenfree for navigation. 
The pupa and nymph 
stages are passed in a few 
4 days and when the period of 
FIG. 216. Long-beaked Mosquitoes, Culex pungens. emergence 1s reached, the 
Adult female and male. Greatly enlarged. nymph case opens over 
the back and the perfect insect appears; which, after drying itself, takes 
wing and disappears. The food of the larve is vegetal substances and the 
minute water infusoria. It is only the female insect which has the pro- 
boscis developed for drawing blood, and both it and the male feed princi- 
pally by sucking the juices of plants at night, the irritation of the bite 
being due to a venomous salivary secretion which probably serves to make 
the blood more liquid. The perfect insect also attacks other insects, cold- 
blooded vertebrates, small fishes, birds and other warm-blooded animals. 
The enemies of the larve and pupz are all the carnivorous insects and 
their larve, tadpoles, frogs, salamanders, newts, minnows, sunfishes, perch, 
sticklebacks, etc.; and those of the adult Dragon-flies are frogs and toads, 
night-flying birds and bats. It was a theory that the female Mosquito 
required animal blood to perfect the eggs, but this is scarcely possible con- 
sidering the enormous numbers of which only an infinitesimal proportion 
ever taste the blood of animals. Mosquitoes are classified as long and 
short beaked. The long-beaked genera of North America are Anopheles, 
Mergarhinus, Psorophora, Toxorhynchites, Stegomyia, Conchyliastes, 
Culex, Uranoteznia and Aédes, of which there are several hundred species. 

265 
