64 
JOURNAL OF ECONOMIC ENTOMOLOGY 
[Vol. 13 
Thus, a combination, rarely to be expected, greatly mitigated the 
damage of 1919. It is hoped that such conditions will prove more 
frequent in the future. It is one thing to note a deficiency of this 
character and quite a different matter to allow such variations to 
materially influence a policy which may have far-reaching effects. It 
is impractical to apply the general code of the criminal law and hold 
an insect incapable of harm until it has proved its ability to cause 
serious damage over wide areas year after year, because such demon¬ 
stration would very probably make it impossible to economically check 
or control the pest. 
Considerable stress (8 p. 66, 9 p. 8410) has been laid upon the practi¬ 
cal immunity in certain small plots at Medford, Mass., of a rank 
growing southern corn and this has been used to support the hope that 
dent corns of the south would escape serious injury. The damage in 
none of these plots was serious and in view of the decided tendency of 
the moths to select early varieties for the deposition of eggs, a habit 
most evident in New York state, we hold it to be unsafe to rely to 
any material extent upon such a slight and comparatively unreliable 
indication. 
The occurrence of but one brood with consequent limitation of 
injury in the infested areas in New York state is conclusive evidence 
of the effect a relatively slight change in climate may have upon this 
insect. Of itself, it justifies a pessimistic attitude toward the reduc¬ 
tion in injury in eastern Massachusetts in 1919, and at the same time 
affords no substantial basis for any such relative immunity for the 
larger portion of the corn belt. There is every reason for expecting 
two and in the more southern portion of the country three broods or 
generations each season. The prolonged period of activity might be 
expected to offset in large measure, at least, any advantage accruing 
to a rank, rapid growing variety of corn. 
The possibilities of clean culture or modifications in agricultural 
methods, likewise appear to be overstressed (9 p. 8410) when it is 
remembered that these conclusions are based upon examinations of 
comparatively few fields and that even in the older infested areas in 
Massachusetts there is considerable local variation in the degree of 
infestation, a condition much more marked in New York state. This 
is no argument against the utilization of such methods to the utmost. 
It is simply a warning against depending upon them to any great 
extent until their utility has been demonstrated. 
There should be due conservatism in the estimation of probable 
injury and the same is equally true, if not more important in regard 
to approximating probable immunity. 
