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 1-J- 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 tobacco being killed. At temperatures below 20° F. 

 the time of exposure in a long series of tests varied from 1^ 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 larva? 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. Larva? 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 lots of 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 larva? 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, larva?, and pupa?, 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. 



