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 larvae 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 

 abdomen free for navigation. 

 The pupa and nymph 

 stages are passed in a few 

 days and when the period of 

 emergence is reached, the 

 nymph case opens over 

 the back and the perfect insect appears; which, after drying itself, takes 

 wing and disappears. The food of the larvas 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 larvae and pupae are all the carnivorous insects and 

 their larvae, 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, Uranotasnia and Aedes, of which there are several hundred species. 



FIG. 216. Long-beaked Mosquitoes, Culex pungens. 

 Adult female and male. Greatly enlarged. 



265 



