NATURAL ENEMIES 
69 
The only record of the attack of this species on 
Musca domestica is by Brefeld. Empusa americana 
seems confined to large flies, like the house fly, the 
blow flies and the like. Doctor Thaxter states that it 
is frequently met with from June to October on the 
borders of woods near brooks or in shrubbery about 
houses. The fly is generally found fixed to the under, 
or rarely the upper, sides of leaves or bare twigs a few 
feet above the ground. It occurs in New England and 
North Carolina. The rhizoids or attaching hyphse, in¬ 
stead of growing out in the form of numerous scat¬ 
tered threads, are developed in an even layer around the 
insect’s body, forming with the conidiophores a con¬ 
tinuous mat-like covering, which often becomes dark 
rust colored on exposure to the weather. 
These are, so far as known, the only true botanical 
enemies of the house fly. Of course, breeding as it 
does in fermenting organic matter and in the dirtiest 
and filthiest locations, and frequenting such situations 
as it does in search of food, it carries upon its body, 
and within its alimentary canal for the brief period 
which it takes for its food to pass through, any num¬ 
ber of spores of fungi and of bacteria, but it is prob¬ 
able that nearly all of these are carried accidentally 
by the fly and do it no harm. Many species of many 
genera of fungi and bacteria have been cultivated upon 
sterilized plates upon which flies caught haphazard 
have been allowed to walk and which they have been 
allowed to speck, but as just stated these are probably 
innoxious to the fly itself. From the observations of 
