Aug. is, 1921 
Dispersion of Flies by Flight 
74i 
this conclusion, especially in the case of the house fly, which showed a 
fairly uniform relation between the number of males and females caught 
in the different circles of traps. Among the screw-worm flies the females 
appear to have shown a slightly more marked tendency toward distant 
dispersion. 
RAPIDITY OP DISPERSION 
In this test it was not possible to get very accurate data on the rapidity 
with which the different traps were reached, owing to the fact that the 
traps were not examined at frequent enough intervals to get accurate 
figures. A number of specimens of house flies were recovered in every 
trap, including the most remote ones, the day following liberation when 
the first examination was made, and the vast majority of all marked 
flies recovered had entered the traps at the end of the fourth day. 
Several specimens were recovered in nearly all of the traps up to the 
eighth day, and a few specimens were recovered after this, the last being 
taken on the twelfth day. It is possible that some may have been 
recovered after this, but as a second liberation was made on that date it 
would be impossible to determine whether the flies belonged to the first 
or second lot. Computation of the percentage of the flies recovered on 
different days in the different circles of traps indicates that the marked 
flies reached the nearer traps somewhat sooner than the more distant 
ones. 
SECOND DISPERSION TEST AT DALLAS, TEX., 1916 
On July 11, 1916, at 12.45 p. m., about 8,000 flies, marked with red 
chalk, were liberated at the same point as in the previous experiments. 
These consisted of about 70 per cent Musca domestica , 25 per cent 
Chrysomya macellaria , 4 per cent Phormia regina , 1 per cent Lucilia 
sericata , Ophyra spp. and Sarcophaga spp., etc. On July 12, during the 
forenoon, a second liberation of about 25,000 marked flies was made. 
This lot was estimated at about 50 per cent M. domestica , 40 per cent 
C. macellaria , 9 per cent P. regina , and 1 per cent L. sericata , Sarcophaga 
spp., etc. Part of these flies were colored with paint pigment known as 
“fast red” and others with powdered chalk. At the time of release a 
7- or 8-mile breeze was blowing from the south, the sky was clear, and 
the sun was very hot. 
In this test the traps in the first and second circles of the previous 
experiment were moved beyond the outer circle in the previous experi¬ 
ment, the traps in circles 3 and 4 in the previous experiment becoming 
numbers 1 and 2 in the present test. The environment of these eight 
traps has been mentioned in the discussion of the previous experiment. 
The positions of the outer rings of traps are briefly described as follows: 
West, No. 3, by farm lot in trees, stable and house 50 yards distant; 
No. 4, by grocery store in edge of city of Dallas. North, No. 3, in edge 
of cornfield % mile north of the village of Reinhardt; No. 4, in cornfield 
