326 ENTOMOLOGICAL SOCIETY 



The highest temperature was found about i or 2 feet below the 

 surface. Within this area the beetles were very numerous. By 

 weighing a quantity of the middlings, and counting the beetles 

 taken therefrom, I found about fifteen hundred beetles to a pound 

 of the middlings. I found 103 from a single ounce, which would 

 make 1,648 to the pound. But the beetles are very small; a 

 hundred weighed only 23 grains. Hence to the pound of the 

 material there would be about 345 or 350 grains of beetles, or 

 about g 1 ^- of the whole weight. 



As the middlings are fed to hogs chiefly, this large percentage 

 of animal food will likely produce no serious results, though it 

 might affect the more sensitive palate of the cow. 



There are, so far as I know, but three other records in regard 

 to the production of heat in grain by insects. Two of these refer 

 to the work of Bruchus scutellaris in pease. The first reference 

 to the subject was by Judge Lawrence Johnson, recorded by Mr. 

 L. O. Howard in Insect Life, Vol I, page 59. He found the 

 temperature of the pease 25 F. above that of the atmosphere of 

 the room. The second observation was by Mr. William D. 

 Richardson, of Fredericksburg, Va., August 13, 1891, published 

 in Insect Life, Vol. IV., page 16, issued November. 1891. Mr. 

 Richardson found the temperature of the infested pease 18 F. 

 above that of the atmosphere. This temperature continued two 

 weeks, when it began to fall, the beetles soon after ceasing to 

 emerge. 



Prof. A. J. Cook* states that this beetle has been known to pro 

 duce heat in grain, but gives no temperature record. 



I am therefore enabled to put on record a rise in temperature 

 caused by insects, more than double that observed by Judge John 

 son, and lacking but i F. of being three times as great as that 

 observed by Mr. Richardson. 



The interesting question now remains, What caused the heat? 

 In the case of Bruchus in pease it has been thought due entirely 

 to the mechanical action, or friction, of the beetles in gnawing 

 their way out of the pease, and this seems probable from the fact 

 that when the beetles ceased to emerge the temperature fell ; but 

 with Silvanus in bran or middlings there is no gnawing-out 

 process. The larvae pupate in the loose material. It seems 

 hardly probable that their crawling through or feeding upon the 

 loose particles could produce so much heat. In order to test this, 

 I allowed some beetles to fast one or two days ; I then placed the 

 bulb of a chemical thermometer in a tube, and filled it about an 

 inch deep with beetles, which struggled and wriggled vigorously, 

 but they had no appreciable effect upon the mercury. After sev 

 eral hours, I put in a quantity of the bran, and though the beetles 



*Rept. Mich. Board of Agr. for 1889, p. 150. 



