COLOR CHANGES IN DYNASTES TITYRUS 443 



of the room. It may be sixty seconds as compared with one 

 hundred and twenty seconds. On another trial the dark red 

 beetle changed to yellow in two minutes when put into arti- 

 ficially dry air, and in four minutes in air of room. When onto 

 the elytra of a dark living male, some phosphorus pentoxide 

 powder was put, that spot changed at once to light yellow with 

 evolution of such heat as to cause a strong reaction from the 

 beetle. 



The difference in rate of color change from yellow to red and 

 from red to yellow is well shown when the beetle is held in run- 

 ning water and then put in the air of the room. The running 

 water does not seem to wet it, that is, it glides over its surface 

 without apparently sinking in, so that when the beetle is re- 

 moved its polished surface seems dry save for a few drops of 

 adhering water, but the color changes slowly from yellow to 

 dark red extending from some regions to entirely embrace all 

 the thorax and the elytra. To complete the change about a 

 minute and a half was needed. 



When the same beetle, now all dark, is placed on the table, 

 it begins at once to turn yellow, so that yellow is visible in five 

 seconds and by the end of sixty seconds all the elytra surface 

 and most of the thorax is yellow, with, however, clouds of dark 

 on the thorax still remaining. 



The assumption that the material of the thorax and elytra 

 is such that it responds with great delicacy to slight changes in 

 moisture in the air and not merely to actual wetting with large 

 amounts of water is sustained in the next section. 



PART 2 



Having tentatively reduced the external factors that seemed 

 responsible for changes in color in these beetles, to changes in 

 moisture, the internal factors due to the beetles being alive needed 

 to be considered. 



Having in the museum a male specimen mounted by Prof. 

 Otto Lugger some time prior to 1885, it was suggested by Mr. 

 M. G. Gichner that this be tried in comparison with the living 



