8 BULLETIN XO. 200, -TJ. S. DEPARTMEXT OF AGRICULTURE. 
this date, in no case do the highest counts rise to the level of the 
lowest counts made before August 10. 
In one respect these counts hardly give a fair indication of the 
effect of the maggot trap, this for the reason that the college kitchen 
was closed from August 7 to September 7. It will be seen that flies 
almost completely disappeared from the kitchen during the latter 
part of August, but as soon as the garbage pails were again in use the 
fly counts go up fairly high, although not as high as the lowest count 
at this place before the experiment started. It is interesting to note 
that while the kitchen was closed the fly counts at the stable were 
somewhat increased and that after the kitchen reopened the flies 
almost disappeared from the stable. Taking the counts at the 
kitchen, we find that the average of the 10 counts before August 10 is 
2,131, while the average of the 10 counts after August 10 is 692, an 
average reduction of 67.5 per cent. At the stable the average of 9 
counts before August 10 is 1,038, and the average of 12 counts after 
August 10 is 248, an average reduction of 76 per cent. 
The behavior of the horses standing in the stalls was also a fairly 
good index of fly prevalence in the stable. As noted above, the 
horses were constantly tormented during June and July. During the 
day the stamping of feet and switching of tails was incessant. After 
the maggot trap had been in operation for some time there was a 
noticeable change. The horses stood much more quietly, and their 
efforts to get rid of flies were less continuous. Several men at the 
college observed this and volunteered the information. 
INFLUENCE OF OTHER BREEDING PLACES ON THE NUMBER OF FLIES 
AT THE COLLEGE. 
If the maggot trap was really destroying 98 per cent of the flies 
breeding in the manure at the college stable, why is there not a corre- 
sponding reduction in the number of adult flies instead of an average 
reduction of from 67 to 76 per cent ? The third series of observations 
points to a probable explanation of this. As indicated on the map, 
there are several breeding places within 700 yards of the college, 
and 700 yards is well within the range of flight of flies, a fact which 
has been proved by several workers. A few flight experiments with 
marked flies were carried out during the season, not with the idea of 
determining the range of flight, but merely to make sure whether or 
not flies from these various breeding places found their way to the 
college stable and kitchen. 
First, about 600 recently emerged flies were thoroughly dusted with 
finely powdered red crayon and liberated on August 31 at a point 
near the stable indicated by the letter B (fig. 1). The point of 
liberation was about 400 yards west of the college stable and perhaps 
500 yards from the kitchen. In spite of the presence of several houses 
