CIRCULAR 462. U. S. DEPARTMENT OF AGRICULTURE 



the larvae and the eggs, the exposure period for complete mortality 

 was the same for 32° as for 30°. 



In tests with the adults, 200 newly emerged adults were placed 

 in each Petri dish, and 1 or 2 such dishes used in each test. Con- 

 siderably more variation in resistance among individuals was noted 

 in the case of the adults than in the tests with the other stages. From 

 200 to 300 adults were necessary for a significant figure on mortality, 

 whereas 100 larvae were sufficient to give a figure of approximately 

 the same significance. The results obtained with a total of 15.485 

 adult beetles are also shown in figure 1. The adult was slightly 



4 



25 



15 















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- 





















• 



# ; 



s 





























T i 



r ' 



r 



■ 





o 







ADULTS 



EGGS 











a a 







A 

 Q 



A LARVAE 



-x — x-d PUPAE 

























16 20 



0AYS 



28 



32 



Figure I. — Days of exposure required for assuring complete mortality of eggs, larvae, 

 pupae, and adults of the cigarette beetle at various temperatures ranging from 15° 

 to 40° F. 



more resistant to the lower temperatures than the egg and pupal 

 stages. At 10° a 1-hour exposure was lethal, but at 15° a 5-hour ex- 

 posure and at 20° a 2-day exposure was necessary to produce com- 

 plete mortality. In the case of the adults, in contrast to that of the 

 eggs, larvae, and pupae, the exposure at 32° was 2 days longer than 

 at 30°. An exposure of 33 days was required at 40°. 



Of particular interest in the graphs shown in figure 1 is the position 

 of the time-temperature points at temperatures of 30°, 32°, and 36° F. 

 The time required to cause complete mortality in eggs is nearly the same 

 for 30°, 32°, and 36°, only 1 day more being required to produce com- 

 plete mortality at 36° than at 30°. In the next 4-degree rise in temper- 

 ature, however, the time to produce complete mortality was increased 

 4 days. With larvae it requires 2 days longer at 36° than at 30° and 

 32° to effect complete mortality, whereas with pupae a 4-day longer ex- 



