February, '13] DEAN: HEAT FOR MILL INSECTS 41 



No mill could have been given a better fumigation with the gas^ 

 and yet a few months later tliis mill was showing evidence of serious 

 insect infestation. The following spring this mill was given a second 

 fumigation wdth hydrocyanic acid gas. One month later insects were 

 in sufficient numbers to cause trouble. During the month of June, 

 without any change or additional radiation in the heating system of 

 the mill, the heat was turned on one Sunday morning and continued 

 until nearly Sunday midnight. The examination the next day showed 

 that far more insects were killed than in the gas fumigations, and inas- 

 much as the examination several months later failed to reveal a single 

 live Mediterranean flour moth in any stage, the manager of the mill 

 was satisfied that it was a far more effective and practical method. 

 Later additional radiation was installed in this mill, and it now has a 

 most effective system. 



No. 2. During the summer of 1910, a 1,500-barrel mill of Welling- 

 ton, Kansas, was fumigated with hydrocyanic acid gas. The expense 

 of the fumigation was over $225, which does not include the shut-down 

 of three days. Before the summer season had passed, not only the 

 common mill insects were again becoming abundant, but the Mediter- 

 ranean flour moth was doing serious injury. The following summer 

 after installing additional radiation at an expense of not more than 

 that of one fumigation, the mill was heated from Sunday morning^ 

 until Sunday midnight. A careful examination the next day showed 

 that no insect escaped death on the floors where the heat ranged from 

 115° to 130° F. No part of the mill was injured by the heat. The 

 examination one year later showed that the Mediterranean flour 

 moth was completely eradicated. The president of the milling com- 

 pany said of the heating method, ''I am confident that the method is 

 a great success. We find that after subjecting our mill to heat for 

 eighteen hours, not a creature which was exposed to the heat lived." 



Heating of Mills in Ohio.^ Professor Gossard, entomologist of 

 the Ohio Agricultural Experiment Station, in his annual report for the 

 year 1911, recommends the heat as a practical and a most efficient 

 method, and speaks of several mills in which the heat was used suc- 

 cessfully. The millers in his state who have used heat are convinced 

 that it is the cheapest and the most effectual method for the control 

 of mill insects. In Bulletin No. 234 of the Ohio Agricultural Experi- 

 ment Station Mr. W. G. Goodwin, the assistant entomologist, makes 

 the following summary relative to the heat method : 



"It is the most thorough method of treatment for the control of 

 insects infesting flour mills; it requires but one treatment per year ta 



•Annual Report of the Entomologist, Ohio Agr. Exp. Sta., 1911. 



