Aug. 15,1921 
Dispersion of Flies by Flight 761 
DIRECTION OF DISPERSION 
The variation in the distances at which the traps in different directions 
from the point of liberation were located makes it somewhat more 
difficult to determine the tendencies of the marked flies to travel in 
different directions. Although the southeast trap was nearest to the 
point of liberation, it is notable that in it six flies, nearly 50 per cent of 
the marked house flies, were recovered, the next largest number (4) being 
in the two traps to the south, one in the east, one in the north, one in the 
west, and none in the southwest, thus showing with this species a tendency 
to travel toward the south and southeast. On the other hand, the 
tendencies as regards direction of flight of Chrysomya macellaria and 
Phormia regina appear to differ considerably from those of Musca 
domestica, but are themselves similar. Four (44.4 per cent) C. macella¬ 
ria and five (31.25 per cent) P. regina were taken in the west traps, 
two (22.2 per cent) C. macellaria and three (18.75 P er cent) P. regina in 
the southwest traps, two (22.2 per cent) C. macellaria and five (31.25 per 
cent) P. regina in the south traps, one each (11.1 and 6.25 per cent) in 
the east traps, and two (12.5 per cent) P. regina in the southeast, thus 
showing in these species a tendency toward migration to the west, south¬ 
west, and to a lesser degree to the south. 
As is shown in Table XI, the wind during this entire period of recovery 
was very choppy. During the first 2 days after release there was some 
south and southeast wind, but aside from this there was during the 
recovery period a very marked predominance of north and northeast 
wind. This would seem in the case of the two blowflies to indicate a 
tendency to travel with the wind in this test. Up to the end of October 
16, when recoveries of marked blowflies had nearly ceased, there was 
experienced during the daylight hours 68 hours of wind from the north, 
northeast, and east, compared with 17 hours from the west, southwest! 
and south. The drawing of conclusions on this point, however, would 
seem unwarranted owing to the extreme variability of the wind during 
the test. 
A considerable number of house flies taken in the southeast trap and 
of blowflies taken in this and the southwest trap indicates still further 
that dissemination by following vehicles aiong the roads is probably 
not an important factor in this or the previous tests. 
In this test, as in the previous one, the variable wind made it difficult 
to determine whether attractive odors such as those produced by towns 
and cities are an important influence in determining direction or dis- 
tance of flight. 
RELATION OR SEX TO DISPERSION 
In this test all of ( the 13 marked house flies recovered were females, 
as were the 9 screw-worm flies and all but 1 (6.25 per cent) of the 16 
specimens of Phormia regina. The only specimen of Ophyra leucostoma 
taken was a male. 
