Aug. is, 1921 
Dispersion of Flies by Flight 
73 i 
captured in Dallas or Fort Worth at the packing houses and were then 
transported to the point of liberation. The time from placing the flies 
in the cylinders until they were liberated ranged from 1 to 2 hours. 
When the point of liberation was reached the cylinders were slipped 
into a canvas bag one at a time and from 1 to 2 ounces of finely powdered 
red chalk or paint pigment were introduced into the cage, which was 
inverted several times. The top was then removed, and the flies were 
allowed to escape. All flies were then shaken from the cages. 
The number and percentage of the different species of flies released 
were estimated by looking into the screened cylinders. While it is 
realized that this estimate is very rough, the writers’ experience in hand¬ 
ling great numbers of flies in traps has added to the reliability of the 
estimates. In one instance the flies in one trap were killed, and the 
proportion of species and sex was determined by actual count. 
When the flies emerged from the cage they were all distinctly covered 
with the chalk, the majority of them being brilliant red. In one instance 
yellow chalk was used and in another the flies were sprayed with rosalic 
acid, but the yellow color was not so readily distinguished in the mass of 
flies caught in the recovery traps, and not a single fly sprayed with 
rosalic acid was identified when an alkaline solution was applied to the 
specimens taken in the recovery traps. In a few of the liberations a red 
paint pigment was used, and this also seemed fairly satisfactoiy. 
In every case there was a considerable mortality among the flies 
placed in the cages, but it is believed that this was caused more by the 
heat while the specimens were being transported to the place of liberation 
than by the application of the marking agent. That there may have 
been some deleterious effect from the application of the chalk dust can 
not be denied, but the fact that some marked specimens were recovered 
17 days after application indicates that the method of marking was not 
highly injurious. 
ACTION OF FLlKvS WHEN LIBERATED 
All liberations were made on the ground in open fields. In every 
instance a considerable number of the flies were observed to take to 
the air immediately, some passing upward to a considerable height. 
They seemed to fly freely in all directions, but there seemed to be more 
going with the wind or at right angles to it than in other directions. A 
large number settled 011 the grass near by, and many of these were 
observed to be preening themselves in a contented way. In experi¬ 
ments where trees were near at hand large numbers were observed to 
settle on the leaves. Many flies exhibited great thirst, as was shown 
by efforts to procure moisture from the leaves and perspiration on our 
bodies. They persistently stuck to our clothing, hands, and faces, and, 
although the conveyance used was always left some distance from the 
point of liberation, a few flies were in every instance observed to be 
