124 BULLETIN 1476, IT. S. DEPARTMENT OF AGRICULTURE 
tion at the probable centers from which such spread may proceed. 
If there is only a light infestation at these points — for example, if 
cornstalks average only one individual per stalk — the element of 
chance may result in drifting stalks being cast on shore singly. 
The ability of the individual from such a cornstalk to produce pro- 
geny will naturally depend upon whether an individual of the oppo- 
site sex is to be found. When the infestation at the center of the 
spread is of more than a single larva per stalk, a new infestation 
may result from a single cornstalk thrown on shore, since the larvae 
it contains may result in several adults of each sex. While in the 
first instance the carrying of cornstalks by water drift may rarely 
result in new infestations or in infestations only in localities where 
several stalks have been thrown on shore together, in the second case 
infestations are much more likely to result. Furthermore, in the case 
of cornstalks being carried long distances by water, many of the 
larvae contained in such stalks may perish before the stalks are cast 
on shore, but in this case the chance of larval survival and resulting 
infestation is increased in proportion to the rate of the infestation 
of such cornstalks. 
Another reason for apprehension as the infestations increase in 
intensity lies in the breakage of cornstalks because of the feeding of 
larvae of this insect. Heavily infested stalks break over much more 
easily than stalks containing only a few larvae, and for this reason 
they would be much more likely to be swept away by rains or floods in 
the spring. 
A case illustrative of this condition may be mentioned in regard 
to the isolated infestation of the insect in eastern Xew York around 
Albany. The question has been asked, if water drift is an important 
means of dispersion, why has no infestation appeared along the lower 
Hudson to indicate a distribution of this sort from the Albany area \ 
There are two facts that may be offered in reply : (1) The infestation 
in the Albany area has never been heavy as compared with "Xew Eng- 
land infestations, so that the conditions favorable to the establish- 
ment of a new colony, as described in the two proceding paragraphs, 
may not have obtained: (2) the discovery of a new infestation, when 
individuals are few and scattered, is by no means a simple matter, 
and although repeated and careful scouting has failed to bring to 
light any infestations indicative of water spread along the Hudson, 
this is not necessarily proof that such infestations may not eventually 
be found. 
Because it is necessary to face this danger if it exists, the argu- 
ments that seem to support the water-drift theory in the dispersion 
of the insect about Lake Erie are presented, together with remarks 
on the infestation in Xew England. What factors caused the distri- 
bution of the insect about Lake Erie are now of minor importance, 
since the infestation is already general, but it is important that the 
evidence be examined to the end that if it is possible a repetition of 
this occurrence may be prevented. 
The discovery during 1921 that a narrow band of infested terri- 
tory (fig. 50) practically surrounded Lake Erie on the American side 
was rather remarkable. Although the discovery of the infestation 
during that year was not proof that such infestation had originated 
during that or the preceding year, the evidence indicated that the 
infestation was not of Ions: standing and had probably originated 
during 1921. 
