242 ZOOLOGY 



A female may lay from one hundred to two hundred eggs. These 

 are usually deposited in filth or manure. In warm weather within 

 a da}' after the eggs are laid the young maggots, as the larvse are 

 called, hatch. After about one week of active feeding these worm- 

 like maggots become quiet and go into the pupal stage, whence 

 under favorable conditions they emerge within another week as 

 adult flies. The adults breed at once, and in a short summer 

 there may be over ten generations of flies. This accounts for the 

 great number. Fortunately few flies survive the winter. 



The Mosquito. — Among the flies are some of the greatest 

 human pests. The mosquito is one relative which is known to 



Three pupse and two larvae of mosquitoes at the surface of the water, breathing. The black 

 line is the water surface. From photograph from life, twice natural size, by Davison. 



harbor the small one-celled parasite (a protozoan) which causes 

 malaria. Another species of mosquito is a carrier of yellow fever. 

 Mosquitoes lay eggs in tiny rafts of one hundred or more eggs in 

 any standing water. Rain barrels, gutters, or old cans may breed 

 in a short time enough mosquitoes to stock a neighborhood. The 

 larvae are known as wigglers. They breathe through a tube in the 

 posterior end of the body and may be recognized by their peculiar 

 movement when on their way to the surface to breathe. The fact 

 that both larvae and pupae take air from the surface of the water 

 makes it possible to kill the mosquito during these stages by pour- 

 ing crude oil on the surface of the water where they breed. The 

 introduction of goldfish or other small fish into water where they 

 breed is another effective means of kilUng this pest. 



Economic Importance of Other Flies. — Other flies which are of 



