29 THE STABLE FLY. 
when the temperature ranges between 31° and 45° F. This range of 
activity is due to variation in individual flies, to the rapidity of the 
decline or rise in temperature, and to the minimum temperature 
experienced by the individuals. No adults appear to be killed when 
the temperature does not go below 27° F., and some at least are able 
to survive temperatures considerably below this pomt. All of the 
adults at Dallas, Tex., seem to have been killed when the temperature 
reached 8° F. As has been stated, the flies always seek shady places 
during hot weather, but when the temperatures are low they delight to 
dart about in the sun in a manner very similar to that of the house fly. 
The maggots, or larve, are very susceptible to drying. This is 
particularly true soon after they are hatched. Excessive moisture is 
also detrimental to their development, and flooding kills them in a 
few hours. They appear to be able to endure rather high tempera- 
tures when abundant moisture is at hand, although the heat produced 
in manure and straw stacks is often sufficient either to kill them or to 
drive them outward. No doubt the generation of heat within the 
breeding places stimulates the development of the immature stages 
during the fall and winter months. Light is detrimental to the 
development of the larve. When placed in bright daylight, even 
though sheltered from the sun, larvee have never been known to 
complete development. These facts make it possible successfully 
to destroy the pest in this stage of its life. 
The pupe of the insect, being in the resting stage, are much less 
susceptible to all climatic extremes. They appear to be able to with- 
stand low temperatures and are not very susceptible to heat or dry- 
ing, especially after development of the fly has proceeded for some 
time. 
PREDACEOUS ENEMIES. 
Hogs, as well as chickens and other poultry, are capable of destroy- 
ing great numbers of the immature stages of the stable fly. They 
are attracted to the straw stacks and manure piles partly by the grain 
to be found, but incidentally they destroy the maggots and pups 
which they find. A number of insects are also important destroyers 
of these stages. Certain beetles devour them in considerable num- 
bers. The adult flies fall prey to numerous enemies. Among the 
more important enemies of the adults are the large robber flies, which 
may be seen in great numbers around straw stacks, pouncing upon 
flies which are depositing eggs or resting upon straw. A number of 
wasps capture the flies that are attacking stock or flyimg about. 
When filled with blood the adults are comparatively sluggish and 
much more easily caught by these enemies. When in this condition 
spiders often devour numbers of them. 
540 
nreeegee eo nee 
