July 15,1925 Effect of Low Temperatures on Bruehus oltectus 
179 
was whether or not the eggs hatched, not the ultimate development 
of the insect. 
These data further show that at temperatures down to — 8° C. 
a much greater length of time must elapse before fatal results ensue. 
At that temperature all the curves flatten out at about the 24-hour 
period. In passing it should be noted that this temperature is 
approximately the one to which injured specimens supercool in the 
ether bath used in the electrothermal method. 
The highest temperature used, — 2° C. for one week, was not fatal 
to any stage, and Larson and Simmons (10) have shown that a much 
longer period than one week is necessary at 0° C. to insure a complete 
kill. The curve showing the limits of the fatal temperature-time 
zone is therefore very long and with a very gradual slope in the 
upper 8 degrees of below 0° C. temperature. 
it is evident, however, that for lower temperatures a much shorter 
time is necessary. Referring to the curves again, it is seen that 
there was no survival at an exposure of — 20° C. for a period of five 
hours, anti even this period applies only to the hatching of eggs. 
Unemerged adults and pupae could withstand only a very short 
period at this temperature, probably only that period required to 
permit penetration of the temperature into the bean. Adults died 
at an exposure of —17° for less than one hour, while one hour'at 
—14° was fatal to them. 
From 1 Table III it is seen that pupae and advanced larvae continue 
their development even after considerable periods of exposure. 
This is of much interest from the standpoint of physiology, but 
since such development does not continue long enough to permit 
the emergence of tne insect, the curve has been drawn between the 
last points of survival and the first points indicating death without 
regard to whether there was any period of later development or not. 
The data for larvae of known age are not as complete as those for 
the other stages. Table III indicates, however, that the mortality 
zone is the same as for unemerged adults and pupae and advanced 
larvae. As sets of vials containing larvae of several ages were used 
each time, it was possible to show that there was no difference in 
power of reistance between very young larvae and those that were 
well advanced, so that the mortality zone for pupae and advanced 
larvae can safely be applied to larvae of less development. 
Larson and Simmons (10) suggest that the temperature at which 
the colony of weevils was maintained prior to freezing has some 
effect on resistance. To verify this a colony was maintained at 
approximately 0° C. for one week in a commercial cold-storage 
plant. At the end of this time adults, unemerged adults, and pupae 
were subjected to a temperature of 14°. The results indicate that 
no hardening had taken place. Both active and unemerged adults 
were killed by exposure for one hour, while exposures of two hours 
killed the pupae and advanced larvae. An exposure of seven hours 
killed pupae and advanced larvae at —10 . These results are 
essentially the same as with weevils taken from room temperatures. 
