Aug. 15,1921 
Dispersion of Flies by Flight 747 
On September 18, between 10 and 11 a. m., about 20,000 marked flies 
were liberated, and between 3 and 4 p. m., 40,000 were released. These 
flies were secured by means of traps at an abattoir in Dallas, the first lot 
being taken between noon of the previous day and 9 o'clock on the morn¬ 
ing of release and the second lot between 9 a. m. and 2 p. m. on the same 
date. The flies were transported to the point of release in screened 
cylinders containing green branches. They were then well colored with 
powdered red crayon by placing the cylinders in a canvas bag. When 
liberated the flies appeared to be very hungry, and many of them clung 
to our clothing and bodies in an effort to secure moisture, but the vast 
majority flew into the air, some apparently going up 20 or 30 feet and 
disappearing in all directions, but seemingly more going northward than 
in other directions. At the time of release the sky was clear and a gentle 
breeze was blowing from the south. The maximum temperature for the 
day was 95 0 F. All flies were brushed off clothing and cylinders, and 
two stops were made after the scene of release was left in order to make 
sure that no colored flies were following. 
The proportions of the different species released were about as follows: 
Musca domestica 42.32 per cent, Chrysomya macellaria 54.90 per cent, 
Phormia regina 1.25 per cent, Sarcophaga spp. 1.25 per cent, Lucilia seri- 
cata 0.14 per cent, Ophyra leucostoma and O . aenescens 0.14 per cent. 
The approximate averages of the species in the entire catch in the 16 
traps were: Musca domestica 44 per cent, C. macellaria 44 per cent, 
P • regina 1 per cent, Ophyra spp. 0.06 per cent, Lucilia spp. 1 per cent, 
Sarcophaga spp. 8 per cent. 
The proportion of the species among the marked specimens recovered 
was Musca domestica 20 per cent, Chrysomya macellaria 78.84 per cent, 
Ophyra aenescens 1.16 per cent. No marked specimens of Phormia 
regina, Lucilia sericata , or Sarcophaga spp. were captured. Comparing 
these percentages with the percentages of the species released, we note 
that the percentage of Ophyra recovered is over eight times, C. macellaria 
slightly less than one and one-half times, and M. domestica less than 
one-half the percentage released. 
DISTANCE OF DISPERSION 
As is shown in Table V, the number of marked house flies reaching 
the four concentric rings of traps from the center outward was 30, 23, 
11, and 5, a total of 69. Expressing this in percentages, we have 43.5, 
33*3> I 5*9» and 7.3. The maximum distance recorded for this species in 
this test was 8.1 miles in trap No. 4 west, where three marked flies were 
recovered. This was almost equaled in trap No. 4 east (7.9 miles) 
where two colored house flies were recovered. 
