December, '16] dove: wintering of house-fly 533 



depositions. Copulations had been observed in this experiment, and 

 by comparison with similar lots of adults it is certain that the adults 

 were sexuallj' matured. An authentic determination of the fungus 

 was not obtained, but it was apparently Empusa musccp. 



In the experiments with Musca domestica, cited in Table I, no Em- 

 pusa appeared. It seems possible that the fungus develops princi- 

 pally in sexually matured and fertilized flies which do not deposit on 

 account of low temperatures. The fungus appears to occur among 

 house flies only under cool conditions of autumn and the fact that 

 they do not deposit during low temperatures may be the explanation. 



Larval Stages 



Winter depositions have been observed in various instances on warm 

 days at Dallas, Texas. In Table II it will be observed that in Breed- 

 ing Nos. 59, 56 and 58 freshly deposited eggs were obtained, on January 

 14, 1914. These were deposited by clusters of females on a manure pile 

 which was generating heat. The eggs were divided, allowed to hatch 

 and develop; some in the manure pile, some in a small tin box in the 

 house, and some in a similar tin box in a shelter for weather instruments. 

 Adults were reared from the manure pile, by preventing the larval 

 migration, within twenty-three days from hatching and in the house 

 in forty-nine days from hatching. While no adults were produced in 

 the shelter, the length of the larval period was extended to twenty-five 

 days. In the shelter the larvae died when very small and being moist 

 experienced lower temperatures than the air which had a minimum of 

 11.5° F. Similarly, in Breeding No. 57, in which small larvae were 

 taken from infested manure and straw, all died within thirty days. 

 In Breeding No. 97-B, freshly hatched larva? which were kept in a 

 mixture of cold wet manure, to which was added occasional small lots of 

 fresh manure, lived more than sixty-seven days. 



While young larva? are capable of withstanding conditions that will 

 lengthen the periods as shown above, in most cases larvae will become 

 developed before the media becomes cold. Especially is this true in 

 manure piles during the early portion of the winter. In Breeding No. 

 62, 1,400, one half to fully grown, larvae were selected by hand and 

 retained in the same media. This consisted of a mixture of horse 

 manure and decaying straw which was of a cold nature, and was not 

 placed on soil where the larvae could penetrate for protection. Living 

 larvae were present on Februarj^ 5, 1914, which was ninety days after 

 they were placed in the cage. By referring to Table II, we find other 

 instances in which larval periods were greatly extended, and while I 

 am certain that greater periods than these were obtained, the fact that 

 larvae and pupae were both present at the beginning of some experi- 



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