6 BULLETIlSr NO. 200^, U. S. DEPAKTMENT OP AGEICULTUEE. 



some emphasis entirely aside from its bearing on the practical use 

 of the maggot trap. The explanation is probably to be fomid in 

 the changes which take place in the manure heap during storage. As 

 the pile stands it settles considerably, with a consequent decrease of 

 air spaces, and, especially if watered, air does not penetrate far below 

 the surface. Deherain and Dupont (1900) have shown that in manure 

 well heaped so that air can not penetrate readily, the confined gases 

 consist largely of carbon dioxid and methane, and that oxygen is 

 not found except near the surface. It may well be that the lack of 

 oxygen and the abundance of carbon dioxid render old manure 

 unfavorable for the breeding of flies. It may also be that the com- 

 position of the gases in the manure is one of the factors which in- 

 fluence migration and the choice of a place for pupation. 



(V \ \NL/MBEf? WHfCH PUPATED /N THE MA/\/Of?E: 



\\ m/soo 



/ AvERAoe or lo cooA/rs at K/rc/-/e/^ aerof^s augc/st /o-^ 



OF /O COUA/rS AT ff/TCHSN AFTSP AL/CUST /O. 



Ai/£RAG£ OPS COUNTS AT STABLE B£FOP£ ^UaUST /O. 



OPS COUNTS AT STABLE APTEP AUGUST /O. 



Fig. 2. — Graphical representation of the -work of the maggot trap and its effect on the prevalence 

 of flies. (Original.) 



EFFECT ON THE FLY PREVALENCE AT THE STABLE AND KITCHEN. 



Turning now to the second line of observation, it will be of interest 

 to determine to what extent the maggot trap influenced the number 

 of fhes at the stable and kitchen. An answer to this is to be found in 

 the series of fly counts made during the season, both before and after 

 the trap was started. In taking these comits ^'tanglefoot" sticky 

 fly paper was used. The papers were exposed for 24-hour intervals 

 and counted immediately at the end of that period. Figure 3 is a 

 graphic representation of these series of counts at the stable and 

 kitchen. In each case the number given is the total caught on two 

 papers exposed at the same time. At the kitchen the two papers 

 were always exposed in the same way on top of the garbage pails, 

 and at the stable one paper was put on the floor just outside the 



