February, '15] BISHOPP-DOVE-PARMAN: HOUSE FLY BIOLOGY 



69 



uary 16. On February 21, the last fly in the cage died, thus showing 

 that the greatest possible longevity in this test was fifty-three days. 



Turning our attention to our observations and experiments with the 

 wintering of the fly in the immature stages, we find two instances in 

 which we succeeded in carrying the species through in the larval and 

 pupal stages. In one of these tests conducted at Dallas, a large screen 

 cage situated in the country one-half mile from breeding places of the 

 house fly was used. On November 26, 1913, about three barrels of 

 mixed horse manure, cow manure, and straw infested with considerable 

 numbers of larvse of all sizes and puparia were put into the cage. Some 

 adults began emerging in the cage soon after the manure was intro- 

 duced. High water covered the manure pile in the cage early in 

 December, but emergence continued after the water subsided until the 

 end of December. No adults were seen to emerge after December 27 

 until April 16, 1914, when four or five specimens came out, although 

 larvse were found in the manure in considerable numbers up to March 

 21. During the latter part of April and early May the manure was 

 again submerged on account of heavy rains, and during this period 

 observations were not made. It seems certain that some larvse were 

 killed by these inundations. However, on Maj^ 26, six vigorous adults 

 were found in the cage. Observations on emergence were not made 

 for some time after this. 



We thus have shown that the house fly lived in the larval and pupal 

 stages from November 26, 1913, to May 26, 1914, a period of six 

 months. 



It is probable that having this cage placed in partial shade and the 

 inundations to which it was subject retarded the development of the 

 stages, thus accounting for the appearance of adults such a long time 

 after warm weather began. Attention is invited also to the fact that 

 larvse remained alive, apparently developing slowly during warm 

 periods, from November 26, 1913, until March 21, 1914, the last time 

 the manure was examined. This period covers all of the cold weather 

 usually experienced at Dallas. Had the larvse, observed on March 

 21, pupated immediately thereafter and the pupse produced adults in 

 the usual time, the resulting adults would have found prevailing tem- 

 peratures sufficiently high to begin reproduction. Hence, we may say 

 that this demonstrates that the larvse of the house fly may success- 

 fully pass the winter at this latitude. If the manure pile had been 

 larger, so as to generate heat, probably the larvse would have pupated 

 earlier and part of the late winter would thus have been passed in the 

 pupal stage. 



At Dallas, the following monthly mean temperatures were experi- 

 enced during the winter and spring of 1913-14: November, 62.9° F.; 



