442 E. A. ANDREWS 



amount of change, apparently, that results in dry or in moist 

 weather. 



The change from dark to hght may be brought about in several 

 seconds or in several minutes. 



The changes are progressive, being first completed usually 

 on the elytra while not yet finished on the thorax. The yellow 

 color comes on in patches or clouds and leaves the shell for a time 

 marbled or clouded with dark that finally vanishes as if drying 

 away. 



Thus, in one case when the air was moist after rain, a female 

 beetle removed from wet air began to show color change in 

 fifteen seconds, in thirty seconds the shell was blotched, in forty- 

 five seconds the blotches of yellow were larger, in one minute 

 the dark was reduced more, in two minutes there were still 

 blotches of dark remaining but in three minutes the elytra 

 were all yellow on the background and the thorax was about 

 half yellow and half dark, in five minutes there still remained 

 some sooty clouds on the thorax. The same beetle on two other 

 days showed the beginning of bleaching on removal from wet 

 air within five seconds, and was very light in twenty seconds, 

 while in thirty seconds the elytra were the maximum yellow and 

 the thorax yellow with smoky black shades which had disappeared 

 by the end of sixty seconds. 



In various trials with the males the light began to be noticed 

 in ten to fifteen seconds after removal from the wet air, in thirty 

 seconds there was much light on the elytra and some on the thorax, 

 in sixty seconds the elytra were light and only sooty shades re- 

 mained of the dark on the thorax, and these shades might be 

 gone before two minutes from time of change of air. When 

 exposed to strong sunlight the change of color from dark to light 

 was about the same rate as if the animal had been removed 

 from the wet air, but this was true only when there was a large 

 amount of air and a strong side light that might well have quickly 

 changed the degree of saturation of the air. 



When a live beetle was put into an atmosphere dried by phos- 

 phorus pentoxide, the change from dark to light color was, in 

 most cases, more rapid than when put from moist air into the air 



