Aug. is, 1921 
Dispersion of Flies by Flight 
737 
the north light travel. Freighting trucks and dairy wagons pass on tlie 
east and west road. 
On June 30, at 11.00 a. m., a second liberation consisting of about 
25,000 flies marked with red chalk was made at the same point as the 
first. The species in this lot were in about the same proportions as those 
in the first release, with possibly somewhat fewer house flies and a few 
more screw-worm flies and Phormia regina. 
Immediately after these flies were liberated the flies in the recovery 
traps were killed and removed for examination, and these examinations 
were made at approximately daily intervals up to and including July 11, 
with the exception of July 2, 4, and 9. The bait pans were replenished 
each day that the flies were removed from the traps. 
It is interesting to note that the proportion of the species among the 
marked flies recovered is very similar to the proportion of those species 
among the flies released. These figures are given for comparison: Musca 
domestica , 70 per cent released, 77 per cent recovered; Chrysomya maccl- 
laria , 25 per cent released, 21 per cent recovered; Phormia regina , 1 per 
cent released, 0.83 per cent recovered; Lucilia spp., Ophyra spp., Sarco- 
phaga spp., Synthesiomyia brasiliana Brauer and Bergenstamm, 1 per 
cent released, 1.16 per cent recovered. It should be remembered that 
the percentages of the species released are only a rough estimate. The 
percentage, of the different species in the total catch during the recovery 
period was not determined; hence it can not be compared with the 
marked flies released and captured. 
distance of dispersion 
The essential data in these experiments as regards the number of flies 
recovered in traps set at different distances in different directions are 
presented in Table II. It will be noted that in general the closer rings 
of traps caught more flies than those at greater distances, although in 
the outside circle of traps the number of flies taken was greater than in 
the third ring. This may undoubtedly be explained, at least partially, 
on the basis of the more advantageous positions where some of the traps 
in the fourth circle were set. The influence of immediate environment 
on the recovery of marked flies will be discussed under some of the 
subsequent experiments. 
