June, 1917] Winter Observations of Muscid Flies 287 



Sufficient artificial heat and the presence of breeding media, 

 however, will result in different observations. Thus in Colum- 

 bus, Ohio, Musca domestica was found in all stages, egg, 

 larva, pupa and adult, all winter in the favored environment 

 prevailing in an animal house where the temperature was 

 regulated to 70°. Similar conditions were found in the green- 

 house-insectary, where flies were bred from fish, meat and 

 manures. At the Columbus Garbage Disposal Plant these 

 flies were common during the winter, breeding in the thick 

 moist drippings from the vats. In the winter 1914-15, from 

 December 7th to May 21st, the author succeeded in producing 

 6 generations of houseflies from horse manure in a greenhouse 

 at College Park, Maryland. 



Manure piles were also investigated for the immature 

 stages. Significant observations were obtained in Maryland. 

 Large masses of puparia were taken from the north-east corner 

 of a maggot trap containing horse manure on the 2nd and lOth 

 of December, 1914, and on the 13th of January, 1915, then again 

 from the south side of the same pile on the 13th of May, 1915. 

 Some advantageous effect produced by the trap prevented the 

 rearing of adults from these puparia. Probably draining the 

 pile, thus loosening it, retards heating by fermentation, allows 

 abundance of ventilation and the corresponding decrease in 

 temperature of the pile. Furthermore, an examination of the 

 puparia still in the pile in the spring revealed no emptied 

 pupae shells from normal emergence. The revealing of so many 

 puparia on the manure pile on the trap from very early winter 

 and then throughout the winter apparently indicates that under 

 natural conditions the housefly hibernates as pup«. At 

 Columbus, however, several scattered batches of eggs were 

 found but these did not hatch when placed in the insectary. 

 Maggots of the housefly were not taken in these situations this 

 winter. Puparia, however, were collected January 6th in 

 guinea-pig manure pile containing rabbit and pig carcasses 

 on west side of Animal House. They w^ere brought into the 

 laboratory where a male Musca domestica L. emerged the next 

 day. A very large mass of puparia was found February 26, 

 1917, about 2 inches above the surface of the ground and about 

 2 feet within the southwest edge of a pile of sheep manure. This 

 manure was undisturbed all winter, except for the addition of 

 cleanings from the sheep sheds. This mass of puparia was 



