1915] Lyon — Does the Housefhj Hibernate as a Pupa? 141 



consisting of one hundred piipse. These were buried in wet and 

 dry sand, wet and dry loam, wet and dry horse manure and in leaf 

 mould. These materials, together with the pup», were placed in 

 large glass jars, covered with cloth and the whole divided into four 

 series. One series was placed out of doors under sheltered condi- 

 tions, one under exposed conditions, another in an unused green- 

 house and the last in the basement of a large stone building. 



The experiments were started on October 19, 1914, and flies con- 

 tinued to emerge till December first from the jars stored in the 

 basement. Two hundred and ten adults emerged from nine 

 hundred pupae, the greatest number coming from the dry manure, 

 wet sand and wet manure. The temperature of the basement was 

 about 60° F. during the entire winter. 



In the unused greenhouse, which was somewhat warmer than 

 out of doors, three hundred and sixty-four adults emerged from 

 eleven hundred pupte, the greatest numbers emerging from wet 

 manure and dry sand. The last adult emerged on November 

 twenty-fourth. 



No adults emerged from the jars out of doors, although the 

 weather was very mild, with the temperature only slightly lower 

 than that in the unused greenhouse. 



Observations were made daily and no adults emerged after 

 December first. On June 23, 1915, the jars were opened and the 

 contents examined. No parasites or fungi were found and the 

 pupse appeared perfectly normal, but on being broken open they 

 were found to have completely dried out. This condition was ob- 

 served in all the jars. 



The results of these experiments, which represented quite nat- 

 ural conditions and the especially favorable conditions of the 

 basement of the building, seem to indicate that the housefly can 

 not easily overwinter as a pupa, although it can emerge until the 

 middle of winter. It would seem, therefore, that the appearance 

 of seemingly freshly-emerged adults in any considerable numbers 

 during late winter and early spring should be accounted for in some 

 other way. 



