HABITAT OF HOUSE FLIES. 83 



is obviously incompetent to destroy them, it is useless to 

 speak of them further. Flies breed in organic matter of 

 every description, animal as well as vegetable. The large 

 majority of them are limited in their destructive effects, 

 filling humble offices in the great scheme of Nature, and 

 unrecognized and unrecorded except in the collection of 

 the specialist, check lists, and agricultural reports. Many 

 species of ISIuscidae are able to retain their fecundated 

 eggs until hatched in a receptacle provided for that pur- 

 pose, and are able to excrete the living maggot directly 

 and in considerable and surprising numbers. I have 

 seen a female of this family rapidly moving ov^er a small 

 quantity of freshly deposited dung, and voiding maggots 

 at intervals of several seconds, until at the expiration of 

 two or three minutes the entire surface of the material 

 was plentifully sprinkled with their writhing forms. 



The house fly breeds in freshly deposited stable manure, 

 and its four stages or transformations occupy, at most, 

 some fifteen days ; M. csesar and vomitoria occupy about 

 the same period. There is practically no stated limit to 

 the number of broods in a season, and it is probable that 

 every hour of the day, from April to December 1st, the 

 several transformations are occurring contemporaneously 

 among the different broods. 



II. Experiments ix Rearing. 



To satisfy myself on the question of the rapid develop- 

 ment of the house fly, a quantity of horse manure was, 

 in the latter part of August of this year, placed on the 

 surface of loose soil with which a soap box was partially 

 filled, and exposed to the sun in my back yard for one 

 day, at the end of which time a glass pane M^as placed 



