THE TOBACCO BEETLE. 43 
of granulated smoking tobacco and passed during the regular course 
of manufacture through the drying processses in use in a large fac- 
tory where smoking tobacco is manufactured. All stages of the beetle 
were destroyed. In one of the driers a temperature of 180°F. was 
reached, which is sufficiently high to sterilize the tobacco quickly 
and effectively. 
In the New Providence factory the leaf tobacco, after treatment 
with vaseline, is compressed into packing cases, placed in drying 
rooms, and subjected to heat for some time. The maximum tem- 
perature reached was found to be about 150°F. This process is used 
for a certain grade of tobacco shipped to Africa and it is said that 
little or no damage has ever been reported from mold or insect 1n- 
jury. In the experiments made (Oct. 20-24, 1915) by Mr. A. C. 
Morgan and the writer to determine the effect of the heating process 
in destroying the different stages of the tobacco beetle, infested 
tobacco was placed in the heating room and a continuous record of 
the temperature obtained by means of a self-recording thermograph. © 
Humidity records were taken at the beginning and close of each 
experiment. Part of the eggs used were on leaf tobacco on which 
they had been deposited, and part in cells on microscope slides, and 
control lots were kept for each of the different stages. In all of the 
controls development was normal, but 1t was found that the tempera- 
ture reached in the heating room resulted in killing all stages of the 
beetle. The details of several of the experiments are given in 
Table V. 
TasLe V.—EHffect of heat on different stages of the tobacco beetle (Lasioderma 
serricorne). EHaperiments at New Providence, Tenn., 1915. 
| 
: T ara- 
Stage of insect. Rela- vonage 
tive Time 
Humid: of ex- Results. Remarks. 
ity. posure 
Eggs. |Larve. | Pupe. | Adults. Min. | Max. 
Percent.| Hh. | OF. | Hours: 
105 41 8 51| 38-40| 97] 140 24 | All stages | Eggs 4 and 5 days old. 
killed. 
114 10 10 Touls8=49 | LOW | 188 Agno oa! doers: Eggs 1 day old. 
32 42 10 28 | 38-49 93 | 140 Qsiltcenee do......| Eggs 1 to 5 days old. 
EFFECT OF HIGH TEMPERATURES ON DIFFERENT STAGES. OF THE TOBACCO BEETLE— 
LABORATORY EXPERIMENTS. 
At Clarksville, Tenn. (1916), numerous laboratory experiments 
were conducted to determine the effect of high temperatures. The 
incubators or ovens used in making the tests were fitted with water 
jackets which permitted exposures to be made without much varia- 
tion in temperature. The different lots were kept with suitable food 
