Aug. is, 1921 
Dispersion of Flies by Flight 751 
of fly activity was from the east and southeast, 44 hours of wind being 
from those directions while the wind came from other directions for 37 
hours, 16 of these being from the north and 7 from the northeast while 
no west or southwest wind whatever was experienced. The fact that 
all the flies captured in the west line of traps were taken on two days, 
September 24 and 25, 5 on the former and 4 on the latter, is peculiar, 
but no explanation is apparent. The prevailing wind on these two days 
was from the southeast and south and on the two days preceding from 
the southeast, while during the days preceding September 22 and 
succeeding September 25 no southwest wind was experienced during the 
period when marked house flies were being recovered. 
The question of the amount of traffic along the highways was men¬ 
tioned in the introductory remarks on this flight experiment. It is 
certainly true that there is far more traffic along the highway running 
north and south from the point of liberation than to the east and west, 
and this corresponds with the greatest dissemination. There is, how¬ 
ever, heavier traffic to the south of the point than there is to the north, 
but many less flies were recovered. There is a comparatively small 
amount of traffic which would induce house flies to congregate and 
follow loads over any of the roads. No doubt the most attractive 
carriers would be milk wagons going into Dallas and returning to the 
rural districts, and these are not very numerous on the highways to the 
north. Other slow-moving vehicles would consist mostly of loads of 
cottonseed hulls and meal, which are not attractive, and miscellaneous 
groceries and supplies which would not be considered especially attrac¬ 
tive. No garbage or manure is hauled over the roads in any direction. 
The major part of the traffic consists of passenger-carrying automobiles 
and some motor trucks. At the time this test was being carried on 
there were many families with various kinds of household goods and 
food driving teams north and south on the main highway. These 
slow-moving covered wagons might readily serve as a means of trans¬ 
port for house flies for some distance. 
The dissemination of Chrysomya macellaria in the different directions 
was much more uniform than that of the house fly. Of the total of 272 
marked screw-worm flies recovered, 81, or 29.8 per cent, were recovered 
in the four traps to the west, 73, or 26.8 per cent, to the north, 55, or 
20.2 per cent to the east, and 63, or 23.2 per cent, to the south. The 
screw-worm fly, which is not especially attracted by urban conditions 
or habitations and is not inclined to come to or be carried by vehicles 
unless loaded with meat or meat products, would not be expected to 
show the same tendencies in dissemination as the house fly, and this 
seems to be indicated by the number of marked flies recovered in the 
different directions. With choppy wind conditions it would be equally as 
hard to determine the wind influence on this species as on the house fly. 
