OF WASHINGTON. 325 



the hind tibia and first tarsal joint, and that in his opinion too 

 much reliance had been placed on this character for the distinc 

 tion of species. 



Mr. Doran read a paper entitled : 



THE EVOLUTION OF HEAT BY SILVANUS CASSIA. 

 By E. W. DORAN. 



February 20, 1892, my attention was called to a bin of bran or 

 middlings, used for feeding stock at the barn of the Maryland 

 Agricultural College, which was badly infested with this com 

 mon red beetle often found in stored grain. On examining the 

 material I perceived at once that it was very warm. Procuring 

 an accurate thermometer, I made the following observations : 

 Time of day, 1.30 P. M. ; temperature of the room, 53 F. ; 

 temperature of middlings, warmest place, 95 F. ; temperature of 

 middlings, coldest place, 42 F. ; difference in temperature of the 

 two points, 53 F. The places where the extremes of tempera 

 ture were found were in the same bin, not more than three feet 

 apart, and at about the same distance below the surface. This 

 extremely high temperature was confined to a small space, not 

 more than two or three feet in diameter, within which the beetles 

 were very numerous, as well as the larvas. The material was 

 perfectly dry, with no indications of mould or ferment. The 

 lower temperature of 42 F., or near that, was found in various 

 places in the same bin, and in other bins and sacks of bran, in 

 the same room. 



Five days later, February 25, I made a second observation, 

 with the following observations : Time of day, 4 P. M. ; tempera 

 ture of the room, 46 F. ; highest temperature of the middlings, 

 86 F. ; lowest temperature of the middlings, 45 F. ; difference 

 between the two extremes, 41 F. ; difference in extremes of two 

 points one foot apart, 20 F. 



One difference between the result of this and the former obser 

 vation is due to the fact that the material had been considerably 

 stirred up in making the examination, and later by those in charge 

 of feeding experiments. However, it will be noticed the actual 

 fall in temperature is only 9 F., though the difference between 

 the extremes is 12 F. less. 



Another examination a week later showed only one or two de 

 grees difference, which may have resulted from still further stir 

 ring of the material. 



At first, as I have said, the beetles were confined to a very 

 small space, though the bin is about 12 feet long by 6 feet wide. 



