44 BULLETIN 137, U. 8. DEPARTMENT OF AGRICULTURE. 
in sealed glass tubes for a considerable time after exposure. The 
eggs used were on leaf tobacco or in cells on microscope slides. Con- 
trols were kept corresponding to the different stages. It was found 
that adults and larve become inactive after a few minutes exposure 
to heat above 117° F., but recover if the temperature is not kept 
higher than 120° F. for a considerable length of time. An exposure 
of 1 hour at 140° F. killed all stages of the beetle in small quantities 
of tobacco but it was found that both larve and pupe are more 
resistant to heat while in the cells formed before pupation, the cells 
serving as a protection. The results of several of the experiments 
are given in Table VI. 
TABLE VI.—EFffect of high temperatures on the tobacco beetle-——Laboratory ex- 
periments at Clarksville, Tenn., 1916. 
Temperature. | 
: : Ex- Mae = 
Stage of insect. posure. Results. Remarks. 
Min. Max. 
JEL OVERS loo TBS |p “IB 
GA TAVCD Ue OU Winen ele soe 1 110 115 | Not effective....| In leaf tobacco. 
Adults and larve...... | 1 110 JO ee ss CKO ER J onllel: In cigar. 
UCI Sa eeae es aes 1 117 10 Iase< OKO, See Became inactive, but recovered after 
: treatment. 
Adults and larve...... 1 128 130) | See doseeee ae Part of each stage killed; remainder 
recovered. 
CSE yee ieee ria 1 128 Sila ME Te Chivies se seeee None of eggs hatched. Check eggs 
hatched normally. Eggs 1 day old. 
AUIStAg eS Aco 2 130 120) esoee GOR aes se Eggs on leaf tobacco. 
CoS tee emer oe 4 138 40 aeee donee In cigars. 
URSA SS eee ere eae 3 138 140 eee dose se Do. 
Larve and pupe...... 1 138 140) ese ce GOss Sake -_...| In yeast cake and tobacco. 
ANIIStagestaes can Skee 1 144 CS esc Oke eee In leaf tobacco. 
DOR ae eo aa 3 146 MEO) Wo esas GO Fe hee ee Do. 
DOR ered aes 3 158 IGE Wescss Goes seeeoee Eggs on leaf tobacco. 
DO ens eee ey 1 158 G5 yee G03 ae eee Do. 
DORM eee ee oe 4 180 | ISTP sos GOERE eer Do. 
In these tests only a small quantity of the food substance was used. 
The time required for treatment will therefore depend on the amount 
and character of the food substance and the insulation furnished by 
the container or wrapping material. The results of the numerous 
tests made show that comparatively mild heat, if long continued, 
is sufficient to kill all stages of the beetle. The temperatures found 
effective are in no way injurious to certain classes of tobacco, which 
in many cases are subjected to a much higher degree of heat in the 
process of manufacture. | 
STERILIZING TOBACCO WAREHOUSES BY MEANS OF STEAM. 
At Quincy, Fla., in July, 1913, an experiment was conducted by 
Mr. D. C. Parman, of this bureau, and the writer in a large warehouse. 
It is the custom of the managers to clean up and sterilize the ware-- 
houses as far as possible, usually by fumigation, before the new crop is 
broughtin. The warehouse used for the experiment was empty and the 
owners: wished to ascertain to what extent steam could be employed. 
