464 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 10 



rapid succession of generations, or if they had keener appetites and a 

 special hking for the codhng moth larvae, the benefit from them would 

 be more appreciable. With their long developmental period, small 

 numbers, and their feeding scattered, both as to kind of larva?, and as 

 to generations of the codling moth larva, the appreciably effective 

 control work done by this species is reduced to a minimum. 

 February 6, 1917. 



HIBERNATION OF THE HOUSE-FLY IN MINNESOTA^ 



By C. W. Howard, St. Paul, Minn. 



The manner in which the house-fly (M. domestica) survives the 

 winter is a matter which has drawn considerable discussion in the 

 last few years. The older theory, that it is the adult fly which passes 

 the winter, for some time gave place to the theory that the winter 

 was spent in the pupal and possibly in the larval stage. The recent 

 work of Bishopp, Dove, and Parman (1915), and of Dove (1916) shows 

 conclusively that in a mild climate such as that of Texas it is possible 

 for both larvae and pupae to pass the winter and adults to emerge in 

 the spring. In cases of mild weather during the winter adults might 

 emerge and oviposit. Nothing has been done to prove whether the 

 same conditions hold for the colder northern regions such as Minnesota. 

 Jepson, at Cambridge, England (1909), was unable to carry pupae 

 through the winter successfully. Newstead in 1909 stated that the 

 most recently emerged flies in autumn may hibernate. On dissection 

 such flies are found to have the abdomen packed with fat bodies in 

 the autumn, but not so in the spring. In 1913 Hewitt confirmed 

 these observations. In a later paper in 1915 Hewitt in some observa- 

 tions on the migration of fly larvae made in the early sirring near 

 Ottawa stated that not a single living pupa was found in the manure 

 or in the soil about the manure pile. He therefore returned to the 

 older theory that the fly overwinters in the adult state in a dormant 

 condition where there is sufficient shelter to protect it from a killing 

 degree of cold, or in places where the temperature and food conditions 

 are suitable to keep it periodically or permanently active. He suggests 

 that the immature stages may survive the winter where temperature 

 and food conditions are favorable, as will be often found in warm 

 stables. Lyon in 1915 in Massachusetts was unable to secure the 

 emergence of adults from puparia exposed to outdoor conditions over 

 winter, although it was a mild winter. 



That flies can be bred during winter under suitable conditions is a 



1 Paper No. 78, Journal Series, Minnesota Experiment Station. 



