26 NEW YORK STATE MUSEUM 
Flight and dissemination. This is something of great import- 
ance in view of the part flies may play in the spread of disease. The 
experiments of Dr L. O. Howard, Government Entomologist, have 
shown conclusively that the major portion of the flics about a 
building breed in the immediate vicinity, probably within 300 to 
soo feet. There is no denying the fact that this insect is capable 
of flying considerable distances but ordinarily this does not seem 
to occur. There is another phase of this question which has ap- 
parently received little consideration, namely, the conveyance of 
flies by vehicles of one kind or another. Only a little observation 
is necessary to show that the butcher cart of the country is a very 
efficient carrier of flies, presumably receiving accessions and leav- 
ing individuals at almost every stopping place, even though the 
route traversed may occupy an entire day. The same is true, 
though to a more limited extent, of trolley cars and express cars 
carrying sacked meat or other supplies 
equally attractive to flies. It is only 
necessary for these carriers to load 
where conditions are favorable for the 
infection of flies and we may have a 
mysterious outbreak of disease at some 
distance from the source of trouble. 
Natural enemies. The house fly, 
though so abundant, is subject to attack 
by various natural enemies. One of the 
most common is a fungous disease 
known as Empusa muscae which 
is occasionally responsible for the death 
of many flies, particularly toward the 
end of the summer. It is not uncom- 
mon to find a few individuals affected 
\ by this disease every year. A small, 
reddish mite may be occasionally found 
attached to flies, seriously weakening 
the host. There are, in addition, wasps 
and spiders which prey upon flies and 
undoubtedly are of considerable service 
PG. TF bok eel he en, though they are very tarelysctxeiently 
still more enlarged. (After Wood) ahundant to materially reduce the num- 
bers of this pest. Another interesting enemy of the house fly 
is known as the house centipede, Scutigera forceps Raf, 

