PROGRESS REPORT ON THE EUROPEAN CORN BORER 121 
The flight of moths from the older and much more heavily infested 
area in Ontario is believed to be the most plausible explanation of the 
origin of the infestation along the shore of Lake Erie in Michigan, 
Ohio, and Pennsylvania, and on the islands in the western end of 
the lake, although no conclusive evidence of this method of intro- 
duction has been established. The possibility that this infestation 
originated from the drift of infested plant material in the waters of 
the lake or from the shipment of infested plant products must also 
be considered. A study of the available wind records of the Lake Erie 
weather stations for the period 1916 to 1921 showed that during the 
flight period of Pyrausta nubilalis the prevailing winds were from 
the southwest, which fact would apparently prevent the possibility 
of the moths flying toward the southern or western shore of Lake 
Erie, but on certain days of that period, particularly during 1921, 
when infestation was first found in the American areas in question, 
the directions of the winds and of occasional summer gales were from 
points north (fig. 49), which would aid the moths in any flight 
toward the American side. According to Crawford and Spencer (72) 
the flight period of the moths in Ontario extended from approxi- 
mately June 16 to July 25 in 1921. During this period the prevail- 
ing winds, particularly during June, blew directly from southern 
Ontario toward the southern and western shores of the lake. (See 
map, fig. 1.) Although the direction of the prevailing winds during 
July, 1921, was from the southwest at most of the lake stations 
where wind records were available, at Erie, Pa., the prevaling winds 
were from the northwest, or from the direction of the infested areas 
of Ontario. Moreover, there were gales from the northwest at some 
of the other southern and western lake stations during this month, 
as shown in Table 40. 
It is apparent from the information shown in Table 40 that there 
was an unusual amount of wind movement from the north and east 
during June and July, 1921, as compared with previous years. The 
fact that the original infestation in Ohio and Michigan was con- 
fined to the islands and the townships bordering the lake, and that 
this infestation followed an unusual amount of wind movement from 
the direction of the infested areas in Ontario, would appear to indi- 
cate the probability of wind spread from Ontario as the causative 
agent. 
