NATURAL ENEMIES 95 



parasite issues through a single rounded hole cut in 

 the pupal skin of the fly. The two sexes issue almost 

 simultaneously, the males a little before the females. 

 Each female appears to lay thirty to forty eggs. Out 

 of 288 specimens reared, eighty-five were males and 

 203 females, and the average duration of the life cycle 

 was nineteen days and seventeen hours. 



Girault will continue his intensive study of fly para- 

 sites and will undoubtedly learn many new and im- 

 portant facts. Additional species have already been 

 reared by him and await systematic study. 



VERTEBRATE HOUSE FLY ENEMIES 



The common garden toad, the great collector of in- 

 sects, will catch a house fly whenever it is able to do so. 

 It is, in fact, a pleasing occupation to feed house flies 

 to a good-sized toad, in order to ascertain his capacity. 

 But these animals are not inhabitants of houses. 



Some of the lizards that run about houses in tropical 

 regions feed upon flies, and the occupancy of houses 

 by these creatures is not objected to by natives, for this 

 as well as for other reasons. 



Birds are not effective as house fly enemies. Of the 

 wild birds, comparatively few feed upon them at all, 

 although there are many insectivorous species which 

 would do so if they were allowed to nest in houses. As 

 a matter of fact, however, in all the records of the Bu- 

 reau of Biological Survey of the U. S. Department of 

 Agriculture, which represent the examination of the 

 contents of the stomachs of many thousands of birds, 



