732 
Journal of Agricultural Research 
Vol. XXI, No. xo 
about the vehicle when the start away from the point was made. The 
flies were at first driven off, and after a short distance had been traveled 
all of those about the vehicle were killed. A second and sometimes a 
third examination were made to make sure that no colored specimens 
were following. 
RECOVERY AND IDENTIFICATION OF FLIES 
In order to determine the distance of dissemination, conical traps 18 
inches in diameter baited with “gut slime” were set at measured dis¬ 
tances in different directions from the point of liberation. The flies col¬ 
lected in these recovery traps were killed at daily intervals as nearly as 
possible, and the mass of flies was carefully gone over for colored speci¬ 
mens. In most instances the colored flies could be identified with the 
unaided eye, but when any doubtful specimens were found they were 
examined with a microscope and the presence of particles of chalk could 
then be determined accurately. During the first few days after libera¬ 
tion most of the flies were strongly colored, but later the specimens 
retained the color mainly on the halteres. 
The sex and species of the marked flies recovered were determined, 
and in many cases the percentage of the different species of unmarked 
flies in the recovery traps was estimated by examination of a certain 
number of flies, and in the same way the sexes were estimated in a num¬ 
ber of instances. The weight of the catch in each recovery trap was 
also determined. 
Owing to the different conditions under which the several dissemina¬ 
tion tests were made it seems best to discuss them separately. 
INITIAL FLIGHT TEST NEAR FORT WORTH, TEX. 
On May 31, 1916, at 1.30 p. m., 7,000 or 8,000 flies were marked with 
red chalk and liberated in an open field about X mile east of the two 
large packing houses which are located approximately 2 miles north of 
Fort Worth. One of the prime objects of this test was to determine 
the freedom with which the flies would go toward packing houses from 
surrounding areas where more or less attractive feeding and breeding 
conditions for flies of all kinds occurred. High teen recovery traps were 
used in this test. They were set at distances and directions as follows 
from the point of liberation (fig. 1): Trap No. 1, 930 feet 15 0 north of west 
on dock of a silo construction company; trap No. 2, 851 feet 15 0 south of 
west on a platform of a plant where dead animals were rendered, hence 
very attractive for flies; trap No. 3, 1,037 feet southwest near a small 
slaughterhouse with surroundings attractive for flies; trap No. 4, 1,323 
feet 12 0 south of west in garden behind store; traps No. 5, 6 , 7, and 8, 
about 2,123 feet 2 5 ° south of west located around a rendering plant where 
conditions were attractive to flies; traps No. 9, 10, 11, 12, and 13, about 
2,588 feet 5 0 south of west and within the inclosure of one of the large 
