Aug. 15 , 1931 
Dispersion of Flies by Flight 
759 
percentage of this species liberated and also about one-half of the per¬ 
centage of this species in the total collection in the recovery traps. 
It should be stated that the weather conditions encountered in this 
test were somewhat adverse, especially as regards variable winds (Table 
XI). Furthermore, the lateness of the season probably had a markedly 
adverse influence on the spread of some of the species, notably Chrysomya 
macellaria , which is preeminently a warm-weather species. The test 
was carried out at a time when the activity and number of C. macellaria 
were declining and the reverse was true in the case of Phormia regina, 
which predominates as a fall and winter species. This is clearly indi¬ 
cated by the diminution in the percentage of these two species of flies 
taken in the various traps. During the early part of the period the total 
captures in certain traps averaged about 20 to 40 per cent C. macellaria 
and 7 to 10 per cent P. regina, while toward the end of the period the 
percentage of C. macellaria dropped to 5 or 10 and P. regina increased to 
20 or 30. The total numbers of house flies captured were fairly large 
throughout the period. 
Owing to the distance which it was necessary to traverse in emptying 
the recovery traps and rebaiting them it was deemed best to make the 
rounds about every three days, hence for the most part the traps were 
emptied, rebaited, and theflies examined on October 12, 15, 18, 21, and 29, 
and others were examined on November 4 and 14. The only notable 
exception to this arrangement was trap No. 2 south, which was emptied 
daily after October 15. The bait in this trap was thus given somewhat 
better attention, and this gave it a slight advantage over the other traps. 
DISTANCE) OF DISPERSION 
The distance the different species of inarked flies had traveled is shown 
in Table X. It will be noted that in general in the nearer traps ranging 
from 7 to 11 miles the major part of the marked flies were captured. In 
the more distant traps ranging from 13 to 15 miles only two marked 
flies were recovered, while in the traps approximately 17 to 18 miles from 
the point of liberation no liberated flies were taken. The maximum dis¬ 
tances recorded for the four species of flies recovered were: Musca 
domestica 13.14 miles, Chrysomya macellaria 15.1 miles, Phormia regina 
10.9 miles, Ophyra leucostoma 7 miles. 
50937°—21 - 5 
