486 
Journal of Agricultural Research 
Vol. XXX, No. 5 
here be summarized for comparison 
with those requirements in America. 
One of the limiting conditions is 
winter temperature. The insects are 
killed by exposure to 0° F., and places 
which normally have subzero temper¬ 
atures,, not accompanied by heavy 
snow covering, are shown to be found 
on the limits of distribution. (Mos¬ 
cow, Astrachan.) 
Warm, dry spring weather is shown 
to be essential to the rapid development 
of the weevil. Such conditions obtain 
in southern France, Italy, and Turkes- 
of about 40° F., four months above 
50° F. and three months above 60° F. 
Cold, damp spring weather favors 
the increase of fungous enemies. Such 
weather is found in Denmark, southern 
Russia, and to a lesser extent in Trans¬ 
caucasia. Months whose mean tem¬ 
perature is above 50° F. have more 
than 2 inches of rainfall. 
No data are available from which to 
determine the factors which limit dis¬ 
tribution on the south. 
For the purpose of applying these 
findings to American conditions they 
tan, and to a lesser extent in Tiflis. 
The spring must be increasingly dry, 
and the summer precipitation must be 
not mpre than 4 inches. Each of the 
months whose mean temperature is 
above 50° F. should have less than 2 
inches of rainfall. 
Damage decreases with an increase 
jn altitude. This is climatically equiv¬ 
alent to an increase in latitude. The 
porthem boundary is found in regions 
having a growing season of about 150 
days, with a mean annual temperature 
are condensed into the following condi¬ 
tions: 
(A) Optima: 
Mean annual temperature 50° F. or above. 
Summer rainfall not over 4 inches. 
No winter temperatures below 0° F. or, if 
below, in combination with heavy, snowfall. 
Growing season of 150 days or more. 
( B) Limits: 
Mean annual temperature below 40° F. 
Summer rainfall over 6 inches. 
Subzero winter temperatures combined with 
light snowfall. 
Growing season less than 100 days. 
