244 PROCEEDINGS OP THE AMERICAN ACADEMY 



hypodermal colors are formed, of course, before the membranes are 

 glued together ; after that time those hypodermal colors are nearly as 

 well preserved as dermal colors, except that they are subject to fading 

 after a lapse of time. The possibility of such an inclusion is proved 

 as a fact by the inclusion of air in the white scales of Lepidoptera. 

 The white mother-of-pearl spots of the species of Argynnis are pro- 

 duced by a system of fine transversal pore-canals filled with air ; by 

 Hydrometra the white ventral marks have the same origin (Leydig). 



The hypodermal colors are mostly brighter and lighter than the 

 dermal ones, — light blue or green in different shades, yellow to 

 orange, and the numerous shades of those colors combined with white. 

 Exceptionally they are metallic, as in Cassida, and are then obliterated 

 after death. The fact which I find quoted, that such metallic colors 

 can be retained in dead specimens by putting a drop of glycerine 

 under the elytra, allows us to conclude that those colors are based 

 upon fat substances. The hypodermal colors are never glossy, as far 

 as I know ; the dermal colors frequently. 



It must not be overlooked that elytra, wings, and hairs all possess 

 a cuticula, and that even here dermal colors are frequently to be 

 found, together with hypodermal ones, chiefly in metallic colors. In 

 the same place both colors may be present, or one of them alone. 

 So we find hypodermal colors in the elytra of Lampyrido?. In the 

 elytra of the Cicindelida? the main metallic color is dermal, the white 

 lines or spots are hypodermal ; by which arrangement the variability 

 in size and shape of those spots is explained. A large number of 

 Lepidoptera have hypodermal colors in the scales of the wings, — a 

 fact shown by the rapid fading of those species. 



There occur in a number of insects external colors, that is, colors 

 upon the cuticula, which I consider to be in fact displaced hypodermal 

 colors, — the mealy pale blue or white upon the abdomen of some 

 Odonata, the white on many Hemiptera, the pale gray on the elytra 

 and on the thorax of the Goliath beetle, and the yellowish powder on 

 Lixus. Some of those colors dissolve easily by ether or melt in 

 heat, and some of them are a kind of wax. I believe that those 

 colors are produced in the hypodermis, and are exuded through the 

 pore canals. Therefore they may be considered as belonging to the 

 hypodermal colors. Eriosoma aim is commonly covered with white 

 waxy secretions. When taken off" gently a new secretion soon begins 

 to appear out of the pores of the four circular glands which are 

 found on each segment of the abdomen. If the dorsal half of the 



