1924] 
Winter Mortality of European Corn Borer 
287 
TABLE No. 6. 
The Effect of Snow Protection on the Extent of Winter Mortality. 
Sweet ( 
:orn (24 
stalks) 
Longfellow flii 
(29 stalks 
it corn 
) 
Total 
No. of 
larvae 
Num- 
ber 
dead 
%of 
winter 
mor- 
tality 
Total 
No. of 
larvae 
Num- 
ber 
dead 
%of 
winter 
mor- 
tality 
Top foot of stalks 
13i0 
67 
51% 
92 
55 
60% 
Middle section of stalks... 
435 
190 
43% 
223 
9j2 
41% 
Bottom foot of stalks 
68 
13 
19% 
49 
13 
26.5% 
It is believed that the top of these stalks was exposed most 
of the winter, that the middle sections were exposed some of the 
time during the winter months and that the bottom foot was 
covered with snow during the whole period of severe winter 
weather. 
Since it has been shown that the variation in winter mor- 
tality of this insect has been quite marked during the two 
winters, 1922-1923 and 1923-1924, it may be useful to examine 
the temperatures of the area covered by experiments during 
these winters. The extent of the area infested by this insect in 
New England is only some 80 miles east and west and about 175 
miles north ands outh, while the extent of the injurious occurrence 
is only a small portion of this area. This is indeed a small area 
in which to study climatic conditions, but on the other hand, 
these conditions will be shown to be quite variable. There is 
considerable difference between the conditions on Cape Cod and 
the winter climate of the hills of Central New Hampshire where 
much more variable winter temperatures are experienced. 
In tables 7 and 8 certain figures are presented for 15 locali- 
ties throughout this larger area. These are divided into groups 
to correspond with the main sections of the area into which the 
results of the study of winter mortality seem to fall. Five locali- 
ties represent the conditions of southern Maine and New Hamp- 
shire; three localities, the river valleys of northeastern Massa- 
chusetts; five localities, eastern Massachusetts and two localities 
