40 JOURNAL OF ECONOMIC ENTOMOLOGY [Vol. 6 



FURTHER DATA ON HEAT AS A MEANS OF 

 CONTROLLING MILL INSECTS 



By Prof. George A. Dean, Entomologist, Kansas State Agricultural College and 



Experiment Station 



Two years ago the writer read a paper before this Association on 

 "heat as a means of controlling mill insects." At that time, although 

 the heat method had been used successfully in one or two flour mills, 

 it was still in the experimental stage. However, within the last two 

 years this method has been so developed that now a large number of 

 mill men are satisfied that it is the only practical and efficient method 

 at present known of completely controlling all classes of mill-infesting 

 insects. In Kansas the heating of more than twenty mills has abso- 

 lutely proven that no stage of an insect, even in the most inaccessible 

 places, could withstand the heat, and several flour mills in Ohio, 

 Illinois, Indiana, Iowa, Nebraska, southern Canada, and elsewhere, 

 have corroborated the practicability and the efficiency of heat as a 

 means of controlling mill insects. 



If a mill is infested with the several stages of the confused flour 

 beetle {Triholium confusum), and the other little rust red flour beetles, 

 the cadell {Tenebrioides mauritanicus) , and the sawtoothed grain beetle 

 (Silvanus surinamensis) , the treatment heretofore used is of little 

 value, for these insects are found in cracks and in accumulations of 

 fine stuffs inaccessible to any gas. After one has visited flour mills 

 throughout this country, and has made inspections of flour arrivals 

 at the principal ports along the Gulf, the Great Lakes, the Atlantic 

 seaboard, and in Europe, he will soon discover that the confused flour 

 beetle and the cadelle, the larval stages of which are causing so much 

 trouble in flour, are found in practically every flour mill in this country, 

 southern Canada, and Europe. After inspecting this flour and the 

 ports of this country and Europe, through which the flour from many 

 of our mills is handled either for domestic or foreign trade, one is not 

 only convinced that it is this class of mill insects that is causing the 

 serious trouble, but that the large majority of the infestations origi- 

 nates at the mills. One will also be convinced that the hydrocyanic 

 acid gas method, as well as others that are in common use, is inade- 

 quate and that something more effective must be used if we are 

 going to control this class of insects. 



A Brief Summary of the Successful Heating of a Few Mills 



No. 1. During the summer of 1910, a 1,000-barrel frame mill in 

 Topeka was given a thorough fumigation with hydrocyanic acid gas. 



