MIMICRY IN THE COLORS OF INSECTS. 889 
colors by interference, and there cannot be more than four, as both 
wings and scales consist only of four layers, two internal belonging 
to the hypodermis, two external belonging to the epidermis. In 
fact, if scales taken from dry specimens of Entimus are observed 
under the microscope, many partly injured can be found, which 
give different colors according to the layers of the lamellæ which 
remain. 
Secondly, colors by interference are produced by many very fine 
lines or strive in very near juxtaposition, as in Apatura and other 
color-changing insects. Colors by interference may perhaps be 
Sometimes also produced in the same way as in the feathers of the 
dove’s neck by very small impressions situated near together. 
The colors produced by the interference of light are only optical 
phenomena, differing in this respect from the other colors of the 
body, the epidermal and hypodermal colors. 
The epidermal colors belong to the pigment deposited in the cells 
of the chitinized external skin, the epidermis. These colors are 
mostly metallic blue, green, bronze, golden, silver, black, brown, 
and perhaps more rarely red. The epidermal colors are very easily 
recognized, because they are persistent, never becoming obliterated 
or changed after death. 
The hypodermal colors are situated in the non-chitinized and 
pi lay er, called hypodermis by Weismann. They are mostly 
brighter and lighter, light blue or green, yellow, milk white, orange 
and all the shades between. The hypodermal colors in the body of 
the insect fade or change, or are obliterated after the death of the 
msect. A fresh or living insect when opened may easily be 
deprived of the hypodermal colors simply by the action of a little 
brush. I said hypodermal colors in the body, because there are 
hypodermal colors which are better protected, being encased nearly 
, ed of the epidermis and hypodermis which become so strongly 
: glued together after the transformation into the imago state 
Mta maceration of years tried by me showed no effect at all on 
= wings. This fact is very interesting as it explains how 
S, and even colored wings, can be found in palzontological 
