318 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 7 



scoop was covered with some drug for several months, and was not 

 disturbed or moved. 



Tenebrioides mauritanicus and Tenebrio molitor. The cadelle beetles 

 are readily killed by 48° C, but the larvse will often live until a tem- 

 perature of almost 50° C. is attained. Moisture, or the lack of mois- 

 ture in the atmosphere, does not seem to make any radical difference. 

 The beetles of the cadelle, and also the darkling beetles, are killed by 

 47° C. to 48° C, but the larva of the former is more resistant and a 

 higher temperature is required to destroy it. The larvae of T. molitor, 

 however, are more suscei^tible to heat in the presence of moisture 

 than in its absence. Larvse of T. molitor died at 46° C. to 48° C. 



Triboliiim confusum. The confused flour beetle is killed by 48° C. 

 and the moisture content of the heated atmosphere seems to make 

 very little difference in results. The slight difference in favor of the 

 moist atmosphere is not sufficiently large to be of any advantage. In 

 fact, taking into account the slower rise in temperature in moist air, 

 the obstruction to the penetration of heat, and the consequent diffi- 

 culty in obtaining a fatal or killing temperature, the dry atmosphere 

 is preferable. The eggs, larvse and pupse are all more readily killed 

 than the adults by the dry heated atmosphere. The adults recover 

 rapidly from the effects of heat if they survive. The larvse and pupse 

 sometimes survive the dry-heat treatment if the killing temperature 

 is rarely or scarcely attained, but all die subsequently, even if trans- 

 ferred to a moist food supply. Larvse and pupse which survive a 

 similar temperature in a moist atmosphere seem in no way inconven- 

 ienced by the treatment they receive, and develop normally. When 

 the confused flour beetles are placed in the oven with a quantitj^ of 

 flour, or middlings, they leave the surface of the material, burying 

 themselves in the cooler parts of their food supply as the temperature 

 rises. When the mass begins to heat through, they attempt to escape 

 the heat by crawling out of the material and soon die on the surface 

 of their food at 47°C, to 48°C. The time required for the heat to 

 penetrate the middlings, or food supply, varies with the material to 

 be treated, its moisture content and also with the intensity of the heat. 

 Flour on the metal bottoms of conveyors will heat through in 3 to 5 

 hours if the surrounding atmosphere is heated to a temperature of 

 55°C. to 60°C. The flour in the conveyors is often 2 or 3 inches deep, 

 so these insects would not be affected by any f umigants excepting the 

 heavy penetrating gases, and would need to be subjected to these for 

 long periods. 



Ploclia interpundella. The Indian meal moth is readily killed by 

 high temperature, 46°C. often proving fatal to larvse, pupse and adults, 

 if continued for several hours. A habit of this species, that of working 



