288 journal of economic entomology [vol. 7 



Temperatures of Manure and Their Significance 



In the course of these experiments some significant observations were 

 made on the temperature of the manure piles. The heating of the 

 freshly piled manure is a matter of common knowledge and observa- 

 tion, but I have not seen any reference to its relation to the breeding 

 of house-flies beyond the general statement that the higher tempera- 

 ture accelerated the development which my own experiments carried 

 out some years ago under controlled incubator conditions demon- 

 strated. Newstead found that at 100° F. the larvae were uncom- 

 fortable and left the manure. In incubator experiments I found that 

 a temperature of 104° F. was too great for the larvae and anything 

 above that roasted them ahve. 



If we examine the temperature of a pile of manure taken at a time 

 when it is fresh, attractive to flies and inhabited by larvae, the results 

 are somewhat surprising and significant. The following are the 

 temperatures which were taken in connection with two of the experi- 

 ments : 



Expmt. No ; 11 (1). 11 (4). 11 (.5). 



Date August 8. August 9. August 15. 



Length of time manure exposed 3 days. 2 days. 2 days. 



Atmospheric conditions Sunny, cool Oppressive, Oppressive, 



wind. alternately sunny alter- 

 sunny. nately. 



Air temperature 86° F. 78° F. 103° F. 



Temp, on surface of manure 97° F. 87° F. — • 



Temp. 1 in. below surface — 106° F. — 



Temp. 4 in. below surface 156° F. 145° F. — 



Temp. 6 in. below surface 158° F. — — 



Temp. 10 in. below surface 164° F. — 160° F. 



From the above temperature records it will be seen that at no 

 great depth from the surface of the manure piles the heat was too 

 great to permit the existence of the larvae, and this fact was supported 

 by observation. On the top of the pile the larvae were only living in 

 the surface layer, that is, the habitat was peripheral and the excessive 

 internal heat due to fermentation becomes practically a larvicide. 



It is evident that in a well-packed manure heap, I am not speaking 

 of small or loosely piled heaps, that only the peripheral region is in- 

 fested by the house-fly larvae, and that they do not, as a rule, penetrate 

 deep into the central regions. In loosely piled heaps it would be pos- 

 sible for them to penetrate more deeply. The cooling of the whole 

 heap might conceivably permit the deeper penetration of subsequent 

 broods, but against this should be set the fact that the outside region 



