120 
BULLETIN 14*16, U. S. DEPARTMENT OF AGRICULTURE 
NATURAL DISPERSION 
FLIGHT OF ADULTS 
From what has been stated concerning the flight and oviposition 
habits of the moths, together with their long period of life, it is evi- 
dent that dispersion by flight is an important factor. It has been 
shown that the moths of both sexes are possessed of strong powers of 
flight and that they have been observed making single flights of 
nearly 300 yards. The duration of adult life as shown in Table 24 
averages approximately between 14 and 20 days for both sexes, thus 
giving the moths ample opportunity for wide dispersion in a series 
of flights, even if each flight was of short duration. In experimental 
tests individual moths of both sexes were recovered at a maximum 
distance of 5 miles on land and 20 miles by water from the point of 
DIRECTION Of PREVAILING WIWGS 
S> — ©-> = JULY 1921 
Fig. 49. — Map of Lake Erie, showing direction of prevailing' winds at principal lake 
ports, from Weather Bureau records, during June and July, 1921. 
the wind 
Arrows fly with 
liberation in the direction of the prevailing wind, indicating that 
they are able to disperse to at least this distance and probably for 
greater distances under favorable conditions. The duration of the 
oviposition period of the females in New England as shown in Table 
24 averages approximately between 10 and 14 days, and by reference 
to Table 38 and the discussion concerning the daily rate of oviposi- 
tion it is seen that the egg clusters are well distributed throughout 
the oviposition period. This affords an opportunity for the females 
to deposit eggs at practically any point to which they may disperse. 
In New England, and to a more limited extent in the eastern and 
western New York areas of infestation, the dispersion has been great- 
est in a general northerly direction. It appears that this direction of 
dispersion may have been influenced by the fact that during the flight 
period of the moths the prevailing winds are from the southwest. 
The transportation of infested plant products or plant remnants and 
the drift of infested material by water must also be considered as 
probably affecting the direction of dispersion. 
