“HOUSE FLIES. 15 
NATURAL ENEMIES. 
The house fly has a number of natural enemies. The common 
house centipede (fig. 9) destroys it in considerable numbers, there is a 
small reddish mite which frequently covers its body and gradually 
destroys it, it is subject to the attacks of hymenopterous parasites in 
its larval condition, and it is destroyed by predatory beetles at the 
same time. 
The most effective enemy, however, is a fungous disease known as 
Empusa musce, which carries off flies in large numbers, particularly 
toward the close of the season. The epidemic ceases in December, 
and although many thousands are killed by it, the remarkable rapidity 
of development in the early summer months soon more than replaces 
the thousands thus destroyed. 
WHAT CITIES AND TOWNS CAN DO. 
It would appear, from what we know of the life history of the com- 
mon house fly and from what remedial experimentation has already 
been carried on, that it is perfectly feasible for cities and towns to 
reduce the numbers of these annoying and dangerous insects so 
ereatly as to render them of comparatively slight account. The 
health departments of most of our cities have the authority to abate 
nuisances dangerous to health, and it is easy for the health authorities 
of any city to formulate rules concerning the construction and care of 
stables and the keeping and disposal of manure which, if enforced, 
will do away with the house-fly nuisance. Such a series of rules was 
formulated in the spring of 1906 by the Health Department of the 
city of Asheville, N. C., and an effort is being made during this summer 
to see that they are enforced. On the 3d of May, 1906, the Health 
Department of the District of Columbia also issued a series of orders 
of this nature, on the authority of the Commissioners of the District, 
and these orders, which may well serve as a model to other communities 
desiring to undertake similar measures, may be briefly condensed as 
follows: 
All stalls in which animals are kept shall have the surface of the 
eround covered with a water-tight floor. Every person occupying a 
building where domestic animals are kept shall maintain, in connec- 
tion therewith, a bin or pit for the reception of manure, and, pending 
the removal from the premises of the manure from the animal or ani- 
mals, shall place such manure in said bin or pit. This bin shall be so 
constructed as to exclude rain water, and shall in all other respects be 
water tight except as it may be connected with the public sewer. It 
shall be provided with a suitable cover and constructed so as to pre- 
vent the ingress and egress of flies. No person owning a stable shall 
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