COLOR CHANGES IN DYNASTES TITYRUS 445 



light formed both upon thorax and elytron of the left side, which 

 was the one illuminated. In one minute the contrast between 

 right and left was very marked indeed. 



Heat 



Standing in moist air with one side illuminated from an elec- 

 tric bulb with naked metal filament shining through some 7 cm. 

 of rather turbid distilled water, the dead beetle remained dark 

 colored more than one hour, but a half hour later when direct 

 sunlight shone along with electric light through water, the beetle 

 had turned light colored on the side toward the light. How- 

 ever, by this time the water was hot and the glass dish next to 

 the beetle felt warm. When removed, this beetle turned pale 

 slate-colored in ten seconds. Even the spots on the side illumi- 

 nated and heated were now still affected by that treatment 

 since they were very pale, while on the side not illuminated they 

 had remained dark red-brown. 



In another experiment, light passing from a tungsten bulb 

 through 7 cm. of water changed color of both elytra and thorax 

 on one side in twenty minutes. While in the above it was at- 

 tempted to cut off heating effects in illumination, in other ex- 

 periments the dead beetle was exposed from one side to heat 

 rays only, coming from electric bulb enclosed in black paper 

 and with all outside light shut off. After an hour the edge of 

 the elytron nearest to the source of heat had turned white while 

 the rest of the elytra and thorax surfaces were dark and very 

 wet with small drops of water collected on it. Removed from 

 the wet air into that of the room, in five seconds the light grey 

 color had spread from the whitened edge of the elytra up nearly 

 to the middle line of the back and also onto the thorax where the 

 heat had evidently produced some effect. In one minute the 

 elytra were most all white even where not exposed to heat rays. 



Moisture 



The first experiment made with this long-dried beetle showed 

 its fine response to moisture; that is, when a cross-shaped piece 



