8 BULLETIN NO. 200, U. S. DEPARTMENT OF AGEICULTUBE. 



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 wiU 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 

 coimts 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 coUege 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 fhes 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 



_ -^._. 



