636 JOURNAL OK ECONOMIC ENTOMOLOGY [Vol. 9 



A Normally Infested Manure Pile During the Winter 



Between October 7 and November 7, 1914, about thirty bushels of 

 cow manure, waste hay, pieces of boards, and rubbish were allowed 

 to accumulate in a pile which, exposed in the open, became most 

 heavily infested with larvae and pupa;. The manure pile being warm 

 from generated heat, the conditions were very favorable for devel- 

 opment, and to be certain that the infestation was mostly Musca 

 domestica, some eight hundred flies were separately bred out by arti- 

 ficial heat. Fresh uninfested cow manure was added to the cage 

 until January 14, and during this time adult house-flies continuously 

 emerged. Additions of fresh manure being discontinued on January 

 14, the generated heat gradually decreased and caused them to cease 

 emerging by January 30. Prior to this date at least 600 adults emerged 

 normally. With their decrease in number the predaceous Scatophaga 

 furcata, as determined by Dr. J. M. Aldrich, increasingly emerged in 

 the cage. This species has previously been pointed out to be preda- 

 ceous upon adult flies and this was fully confirmed by our observations. 

 The manure pile intentionallj^ remained unchanged in size or form after 

 January 14, and no emergence occurred until April 16. On May 5, 

 three other house-flies emerged and emergence continued until June 5, 

 during which time the total number was at least 142. I believe the 

 emergence in the cage would have been a surprising nuniber of hun- 

 dreds had the cage been large enough to allow a margin of a few feet 

 on either side of the manure pile to prevent escape of migrating larvae. 



The migration of larvse has been sufficiently dealt with by Hutchison 

 (1914 and 1915). The larval habit of burrowing into the soil has been 

 graphically illustrated by Dr. C. G. Hewitt (1915). At Dallas, Texas, 

 during the fall of 1914, about 900 adults were observed to emerge 

 into an empty cage six feet from a manure pile; the greatest distance 

 of a single larval migration was at least eight feet. The burrowing 

 depth of the larvse was not determined, but Dr. Hewitt's diagram 

 shows that they have been found in sandy loam two feet deep, and 

 good numbers were present below a depth of one foot. Attention is 

 called also to the fact that the larvee pupated far enough away from 

 the manure pile so as not to be affected by the generating heat. 



The cage of Breeding No. 105 contained the only accumulation of 

 infested manure on the premises, and yet when adults began to emerge 

 in the cage they continuously increased in number on the walls of 

 nearby houses. It is quite evident that this was due to the larval 

 migration from underneath the sides of the cages. 



The failure in so many overwintering experiments to produce adults 

 in spring may be attributed to the absence of soil into which the larvas 

 could migrate for protection. 



