HOUSE FLIES. 9 
fungus. Careful experiments conducted at the experiment farm at 
Arlington, Va., during the winter of 1914-15 showed that flies kept 
in unheated buildings were killed during the first really cold nights 
of the winter. Those kept in one of the greenhouses behaved just 
as they would during the summer at similar temperatures. At tem- 
peratures of 65° to 75° F. very few lived longer than 35 to 40 days. 
The best conditions were found in one of the large stables which was 
slightly heated, the temperature ranging from 382° to 50° F. Some 
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Fic. 12.—Pupe of the house fly. About natural size. (From Newstead.) 
flies were kept alive here for a period of 70 days, a long period, but 
not sufficient to carry them through the winter. 
Regular collections of flies were made at the Arlington farm during 
the winter of 1914-15. No living adult house flies were found after 
the middle of January until April 30, while Pollenia, which does 
hibernate in the adult state, could be found in buildings almost any 
time during the winter, and on warm days they were found outside. 
On the other hand, there are on record some experiments and ob- 
servations which indicate that the usual manner in which the house 
fly passes the winter is in the pupal stage. Bishopp, Dove, and Par- 
man succeeded in two instances in keeping the species through the 
winter in the larval and pupal stages. Three barrels of heavily in- 
94399°— Bull. 679—15 2 
