A MAGGOT TRAP IN PRACTICAL USE. 7 
door and the second just inside the door, which faces the east. On 
several occasions papers were exposed, but the counts are not given 
in the diagram for the reason that a shower of rain or a strong wind 
spoiled some of the papers. The numbers which are plotted are those 
obtained on clear, warm days, on which the climatological conditions 
wore nearly the same except for the direction of the wind. This will 
account for the irregular time intervals between the successive counts. 
It is recognized that this method is not all that could be desired as 
an accurate index of fly prevalence. The use of a small number of fly 
papers in this way is nothing more than a method of sampling, but 
since the papers were exposed always in the same places and under 
nearly the same climatological conditions, the method may be con- 
sidered as reliable as any method of sampling used in other lines of 
Fig. 3.— The broken line connects series of fly counts at the garbage pails near kitchen; the solid 
line, those at the stable. (Original.) 
work. The use of a few fly papers in this way would not of itself 
have any appreciable effect on fly prevalence. It was thought that 
the use of fly traps would complicate the situation in that any appar- 
ent reduction in the number of flies might be ascribed to their use 
rather than to the maggot trap. 
A study of the fly counts shown in figure 3 reveals that there was a 
decided drop in the number of flies both at the kitchen and stable very 
shortly after the maggot trap was put into operation. Assuming that 
all the flies at the stable and kitchen at the time the experiment began 
(July 25) were freshly emerged and that they would all die off within 
three weeks (there is some evidence that flies seldom live longer than 
this in midsummer), one would expect to find a reduction in the 
number of flies about August 10 or 12. As a matter of fact this is 
what occurred. Although the counts fluctuate considerably after 
