1044 
Journal of Agricultural Research 
Vol. XXVIII, No. 10 
this slight increase in temperature associating itself with a marked increase in 
longevity. Specimens of the granary weevil were still alive after an exposure 
to this temperature for 105 days. 
With a temperature ranging from 50° to 60° F., and under the other conditions 
prevailing, the normal lives of both species of weevil were greatly prolonged. 
Adults of the rice weevil confined in a refrigerator with this range of temperature 
lived for a period of 558 days, and specimens of the granary weevil in the same 
refrigerator for a period of 873 days. The normal life of the rice weevil in sum¬ 
mer is from 100 to 200 days, while that of the granary weevil averages from 
200 to 250 days. 
The immature stages of these two weevils show a similar difference in their 
powers of resistance to low temperatures. Eggs of the rice weevil perished after 
being exposed to a constant temperature of 30° F. for 4 days, whereas eggs of the 
granary weevil survived an exposure to the same temperature for a period of 28 
days. Larvae of the rice weevil were killed by an exposure to a temperature of 
30° F. for a period of 11 days, while larvae of the granary weevil survived an 
exposure of 44 days to that temperature. 
The data previously quoted have been derived from experiments with several 
thousand individuals. However, the susceptibility to low temperatures varies 
so much in individuals of the same species that very large numbers must be 
experimented with in order to arrive at definite conclusions regarding the lethal 
qualities of any one temperature. The foregoing figures can not be considered 
quite final until further experiments involving many more individuals have 
been completed. More detailed results regarding the lethal effect of various 
low temperatures on the different stages of these two weevils will be published 
later, when experiments now under way have been completed. 
The effect of high temperatures on the two weevils is also of interest, although 
there are no very great differences in the reactions of the two species to heat. 
With both species constant temperatures above 95° F. soon prove fatal. Of a 
large number of adults of the rice weevil confined in an incubator at a tempera¬ 
ture ranging from 95° to 98° F., all were killed at the end of 9 days. Adults of 
the granary weevil confined in the same incubator were all dead at the end of 13 
days. A temperature of 120° F. killed adults of both species in three hours, and 
a temperature of 130° F. within 30 minutes. It is interesting to note that ovi- 
position ceased at a constant temperature of 94° F. 
