448 E. A. ANDREWS 



when in dry air, and rapidly taking on the light color if rapidly 

 dried and slowly turning red if slowly moistened; it seemed that 

 there must be some special peculiarity of the surfaces of the shell 

 of the animal in those regions which caused it to change color 

 according to its dryness or wetness. 



Whether this change in the shell was chemical; a change due 

 to hydration; or a change due to some physical effect upon light 

 connected with distribution of light was not at first evident. 



The application of other liquids than water and also microscopic 

 observations of the substance of the shell both point to the con- 

 clusion that the causes of the color change in the substance of 

 the shell are physical arrangements of the material that allow 

 of distributions of air that lead to the reflection of yellowish 

 light and on the other hand, substitution of liquids for air and 

 resulting passage of red light or partial absence of light. 



Experiments with other liquids than water 



While a drop of stiff honey on the thorax of a live or a dead 

 beetle neither soaks in nor produces any change in color, at least 

 not for a great many hours, a drop of vaseline acts quite like 

 water. An area covered with vaseline turned black gradually 

 and not uniformly, for some spots remain light longer, so that 

 where vaseline is thickest the shell may remain light, and thin 

 layers of vaseline at the edge of the drop may enter the shell 

 and turn it black. Much later, the black spots so produced 

 were no longer to be seen. 



Xylol instantly blackens the shell but in a minute or so, on 

 drying, leaves the shell again light. The xylol dries out first 

 a,t the center leaving a dark circle for a time. 



Ether dropped on the shell instantly produces a black spot 

 that instantly vanishes with a dark ring remaining a little longer. 



When absolute alcohol was poured over a beetle, its surfaces 

 turned dark at once and returned to the light color as the alcohol 

 evaporated in a few seconds. On the other hand, a dead beetle 

 that was dark from standing in moist air, when brushed over 

 with 95 per cent alcohol did not bleach but when so treated with 



