April, 11] dean: fatal temperatures 143 



ing properties. In the second report of the state entomologist of 

 New York, Prof. J. A. Lintner, in speaking of Tribolium ferrugineum 

 infesting grain and flour says, "A moderate degree of heat, 120° 

 to 130° F., continued for a few hours, would in all probability suffice 

 to kill all the eggs, larvae and pupse in the material, while a higher 

 temperature, perhaps 150° or more, would be needed for the beetles. 

 Prof. F. H. Chittenden in his article on "Insects Injurious to Stored 

 Grain" says, "Prior to the adoption of carbon disulphide as a fumigant, 

 heat was relied upon in the destruction of these insects. A temper- 

 ature of from 125° to 140° F., continued for a few hours, is fatal to 

 grain insects, and wheat can be subjected to a temperature of 150° 

 for a short time without destroying its germinating power." 



Nearly all the experiments of this nature were made relative to 

 the discovery of a method to destroy Angoumois grain moth, and 

 from the results of these experiments some of the experimenters and 

 other Avriters have assumed that many of the grain insects could 

 probably be destroyed in the same manner, but it would require a 

 higher temperature to destroy the adults than the larvae or pupae. 

 Since this method of combating grain insects was not developed and 

 given a practical test in a flour mill, and believing that the death 

 of these insects in the Kansas mills was caused by a fatal maximum 

 temperature, the next step was to determine this temperature and to 

 ascertain whether it would be possible and practical to not only pro- 

 duce such a condition in a modern mill, but whether it would prove 

 fatal to the insects therein. 



In the first experiment about twenty-five individuals of both the 

 adult and larvae of Tribolium confusum were placed in a shell vial 

 and covered with an inch of flour. A thermometer was placed in 

 this vial with the bulb Testing in the center of the flour. The vial 

 containing the flour and various stages of Tribolium confusum was next 

 suspended in a large bottle in such a manner as not to touch the sides 

 of it. This bottle was then placed in a glass jar filled with water, and" 

 this glass jar was placed in a vessel filled Avith water. The heat was 

 applied beneath this vessel. This arrangement reduced to a minimum 

 the unequal chstribution of the heat in the shell vial containing the 

 insects. In raising the temperature from 80° to 90° no change was 

 noticed in the action of these insects. At a temperature of about 

 96° the adults became uneasy and began running around rather 

 rapidly. At a temperature of 100° the larvae emerged and crawled 

 over the flour, and the adults were running more rapidly than at 96°. 

 At a temperature of 110° iDoth larvae and adults were frantic and were 

 making every effort to escape, and these actions were continued until 

 a temperature of 115° was reached. At this temperature both the 



