28 



BULLETIN 812, U. S. DEPARTMENT OF AGRICULTURE, 



lations of fine stocks inacessible to any gas. The flour beetles and 

 the cadelle, the larval stages of which cause much trouble in flour, 

 are in practically every flour mill in the country, except where reme- 

 dial measures are successfully practiced. Inspection of ports in 

 this country and in Europe through which the flour from many 

 American mills is handled, either for domestic or for foreign trade, 

 indicates that these insects just mentioned, which can not be con- 

 trolled so satisfactorily by fumigation, are causing serious trouble, 

 and that the large majority of the infestations originate at the mills. 







-->-• 



Fig. 15. — Photograph of elevator legs after application of the heat method of control. 

 Note the large number of flour beetles which, on feeling the heat, have crawled out of 

 the cracks of the wooden elevator legs and died upon the mill floor. 



The most practical and effective method known to control all classes 

 of mill-infesting insects is the application of high temperatures. (Fig. 

 15.) 



Heat has been recognized as a control agent for many years in this 

 country and in Europe. But its effectiveness as a control measure in 

 Hour mills was first demonstrated by professional experimental inves- 

 tigation by Prof. George A. Dean in several Kansas mills during the 

 period 1910-1913. 4 So successful were Dean's demonstrations that 

 the heat method has been tested by the Federal Bureau of Entomology 

 and by several State entomologists with the result that mills in 



* Dean, Geoege A., mill and stohed-grain insects. 

 189, p. 139-236, 56 figs., 6 pi., July, 1913. 



Kans. State Exp. Sta. Bui. 



