Aug. 15, 1921 
Dispersion of Flies by Flight 735 
It is notable that over 64 per cent of the total number of marked flies 
recovered were found to be captured when the traps were emptied about 
24 hours after the liberation had been made, and several of the traps 
were not examined within this 24-hour period. 
This test also shows that distances up to 1,000 feet are covered in a few 
minutes by flies, that the screw-worm fly may travel nearly half a mile 
in 3 hours, and that the house fly may go over 3,000 feet in less than 48 
hours. 
Since the recovery traps were not placed in all directions from the 
point of liberation, it is very difficult to draw conclusions in this test in 
regard to the effect of wind on dissemination. During this recovery 
period the wind during the daytime varied in velocity from 5 to 30 
miles, and the prevailing directions were south and southeast. 
(Table I.) The wind with a velocity of from 13 to 24 miles blew from 
the southeast and south during the 48 hours following release, and since 
the majority of the marked flies recovered were taken within that period 
it is seen that those captured traveled practically at right angles to this 
wind. 
A second liberation of about 10,000 flies, marked with yellow chalk was 
made at 4.30 p. m., June 1. The proportion of the different species was 
estimated to be as follows: Chrysomya macellaria 60 per cent, Phormia 
regina 28 per cent, Musca domestica 10 per cent, other species, including 
Lueilia, Ophyra, Sarcophaga, and Muscina stabulans , 2 per cent. Diffi¬ 
culty was encountered in identifying the flies from this liberation. None 
were observed except on June 2, when the following recoveries were posi¬ 
tively made: No. 14, 10.15 a. m., 1 9 P. regina; No. 10, 12.30 p. 111., 1 9 P. 
regina; No. 11,2 9 P. regina, 1 $ C. macellaria; No. 13, 1 P. regina, 
1 ? C. macellaria; No. 1, 1.30 p. 111., 2 $ and 1 9 P- regina; No. 2, 1 9 
C. macellaria. This shows that P. regina traveled over 3,000 feet in less 
than 18 hours after release and that night hours were included in this 
period. 
Table I .—Climatological data relating to initial dispersion test at Fort Worth, Tex. 
Temperature. 
Wind. 
Humidity. 
Ac¬ 
tual 
sun. 
Date. 
Max. 
Min. 
Mean. 
Direction during successive 
hours from 6 a. m. to 8 p. m. 
Velocity 
during 
day. 
Rain. 
Max. 
Min. 
Mean. 
1916. 
0 F . 
0 F . 
0 F . 
Miles . 
Inch . 
Per 
cent. 
Per 
cent . 
Per 
cent . 
Per 
cent . 
92 
May 31.... 
94 
70 
82 
14 SE. 
8 to 24 
0 
76 
39 
56 
54 
June 1.. .. 
95 
72 
84 
14 s. 
15 to 24 
0 
75 
34 
43 
70 
2 .. .. 
96 
75 
86 
2 S., 4 SW., 2 NW., 3 W., 3 NW. 
2 NE., 9 SE., 1 S., 2 SE. 
5 to 21 
0 
76 
60 
87 
3 • • • • 
94 
72 
83 
5 to 13 
0 
70 
49 
60 
80 
4 . . . . 
« 7 
75 
81 
14 SE. 
8 to 26 
0 
77 
50 
39 
64 
52 
5 • • • ■ 
86 
70 
78 
2 a, 5 sw., 5 w., 2 NW. 
19 to 30 
0 
03 
54 
73 
