42 THE BOOK OF THE FLY 



intended food. By the use of her soft, slender ovipositor, 

 which is telescopically extensile and flexible, the eggs 

 are deposited in shaded and concealed situations. 



The house-fly is credited with laying batches of eggs 

 at intervals, perhaps four or more times, and about 150 

 on the first occasion, then 100, and less on subsequent 

 occasions. Under favourable circumstances the eggs 

 may hatch within a few hours of their being laid. 

 The maggots of midsummer broods may be full grown 

 and pupate in six days, and the perfect insect may 

 emerge from the puparium in another ten days of warm 

 weather, but in cold weather the pupa; of autumnal 

 broods may remain dormant for several weeks, or even 

 months. When nine or ten days old the mature fly may 

 begin to lay eggs ; hence, with such a life-cycle, in a 

 month of very favourable weather the progeny of a 

 single pair may number, say, 500 ; in two months' 

 time the number may become 250 times 500 ; and in 

 three months' time many millions ! 



