Aug. 15,1921 
Dispersion of Flies by Flight 
757 
FOURTH DISPERSION TEST AT DALLAS, TEX. 
Since marked specimens of both the house fly and the screw-worm 
fly were recovered to the maximum distance afforded by the recovery 
traps in the third dispersion test, it was decided to perform another 
experiment with the recovery stations at still greater distances from the 
point of liberation. The same point for liberating the flies was used in 
this test, but owing to difficulties encountered in collecting the flies and 
rebaiting the recovery traps to the north it was deemed advisable to 
set only two traps in that direction. The number of traps to the south 
was also decreased to two; the number east and west was increased to 
five in each direction, and one trap was placed in the southeast quadrant 
and one in the northeast quadrant in order to show more clearly whether 
or not the flies were following the main arteries of traffic which run ap¬ 
proximately north and south and east and west. 
The location of the traps in this test is indicated in figure 2. Their 
immediate environment and distance from the point of liberation were 
as follows: West, No. 1, 9.5 miles, in the edge of the town of Farmers 
Branch, some poultry and a cow on adjacent lot; No. 2, 10.9 miles, near 
farmhouse, hogpen, mule and cow lot adjacent; No. 3, 13.2 miles, under 
tool shed at a ranch headquarters, considerable live stock kept near by; 
No. 4, 15.8 miles, under sheep shed on farm, horses, mules, and hogs 
near; No. 5, 17.8 miles, against chicken house on farm, some hogs and 
mules 100 yards away. North, No. 1, 13.14 miles, in edge of town of 
Allen, in yard near hogpen; No. 2, 16.85 miles, in old bam on farm, 
hogs and mules in barnyard. East, No. 1, 9.3 miles, on farm, hogs, 
cows, and horses in barnyard; No. 2, 10.8 miles, under shed on farm, 
many pigs, sheep, and other animals in yard and small slaughterhouse 
100 yards distant; No. 3, 13.1 miles, under water tank on farm, all 
classes of stock in adjacent yard; No. 4, 15.1 miles, under shed on farm, 
mules, hogs, and cattle near; No: 5, 17 miles, in shed adjacent to hog¬ 
pen on farm, mile beyond town of Rockwall. South, No. 1, 8.2 miles, 
under tree in edge of Dallas, no live stock near (same situation as trap 
No. 4 in previous test); No. 2, 9.7 miles, at laboratory in middle of 
residential section of Dallas, live stock kept in yard. Southeast, so 
designated, one trap 7 miles from point of liberation being 2.5 miles 
east of south, yi mile northwest of town of Reinhardt, under shed by 
barn, live stock in yard. Southwest, so designated, one trap 10 miles 
from point of liberation, 4 miles south of west from that point, placed 
by empty bam with house, hogpen, and horse lot near by. 
The traps to the west, north, east, and south were located on the same 
roads as in the previous test. The southeast trap was near a main 
highway running northeast from Dallas to Garland, where it forms a 
juncture with a macadamized road running east from the point of libera¬ 
tion. Very little if any traffic would pass directly by the point of 
liberation and around by this trap. 
