40 BULLETIN 737, U. S. DEPARTMENT OF AGRICULTURE. 
Most of the tests recorded in Table IV were made with the different 
stages of the beetle in smoking tobacco. In this series the time of 
exposure to cold varied from 14 hours to 5 days. The treatment did 
not prove completely effective on all stages of the beetle at tempera- 
tures between 14° and 16° F. with exposures under 5 days. In all 
experiments under the same conditions exposures of over 5 days 
gave satisfactory results, all stages of the beetle in various classes of 
manufactured tobacce being killed. At temperatures below 20° F. 
the time of exposure in a long series of tests varied from 13 hours 
to 56 days. Experiments with infested tobacco exposed for 56 days 
at temperatures between 33° and 40° F. were not entirely satisfactory, 
a few larve remaining alive. For short exposures it was found that 
results depended largely upon the insulation afforded by wrapping 
and upon the quantity of material used. Larve within the cells were 
found to be more resistant to cold than other stages of the insect. 
After treatment the material used in the experiments was placed in 
an incubator and kept for some time under observation at a constant 
temperature of 86° F. 
Six additional experiments were made with cigars that were heavily 
infested. The boxes were wrapped with paper and kept in cold stor- 
age in sealed metal containers. The temperature varied from 12° to 
20° F., but was fairly constant at 14° F. The time of exposure was 7 
days for three experiments, 21 days for one experiment, and 31 days 
for two experiments. All stages of the beetle, including large numbers 
of eggs, were present in five lotsof cigars. In the experiment in which 
the time for exposure was 21 days two boxes of 25 cigars each, in 
which large numbers of newly hatched larve had been placed, were 
used. In all the experiments the treatment proved completely effec- 
tive. The boxes were kept under suitable rearing conditions at 
the Richmond laboratory for several months and no reinfestation 
developed. 
At a temperature of approximately 14° F., three separate tests 
were made with cigarettes. Three boxes containing 100 cigarettes 
each, heavily infested with adults, larve, and pup, were utilized, 
the duration of the experiments being 14, 15, and 42 days respec- 
tively. In each lot all stages of the beetle were killed. In another 
series of experiments 30 separate tests were made with various quan- 
tities and classes of manufactured tobacco. The temperature of the 
cold-storage room was fairly constant, approximating 14°F., the 
variations during the entire period being from 12° to 18° F., and the 
relative humidity ranging from 84 to 90 per cent. In these as well 
as other experiments temperature and humidity records were obtained 
by means of a self-recording thermograph and hygrograph. Part 
of the material was exposed in air-tight containers and part exposed 
in the original containers, not sealed, or in paper-wrapped packages. 
