COLOR AND COLORATION IJI 



sumption, in the case of insects, and one that is inadequate in spite of 

 its plausibility, for (i) it is extremely improbable from our present knowl- 

 edge of insect vision that insects are able to perceive colors except in 

 the broadest way, namely, as masses; (2) the great majority of insect 

 species show no sexual differences in coloration; (3) when colorational 

 antigeny is present it is probably unnecessary, to say the least, for "sexual 

 recognition. Thus, notwithstanding the marked dissimilarity of colora- 

 tion in the two sexes of C. promethea, the males, guided by an odor, seek 

 out their mates even when the wings of the female have been amputated 

 and male wings glued in their place, as Mayer found. 



Hence, when useless, colorational antigeny cannot have been de- 

 veloped by natural selection and may be due simply to the extended 

 action of the same forces that have produced variety of coloration in 

 general. 



Origin of Color Patterns. Tower, who has written an important 

 work on the colors and color patterns of Coleoptera, finds that each of 

 the black spots on the pronotum of the Colorado potato beetle (Fig. 238) 

 "is developed in connection with a muscle, and marks the point of at- 

 tachment of its fibers to the cuticula." Thus the color pattern, in its 

 origin, is not necessarily useful. This point is so important that we 

 quote Tower's conclusions in full. "The most important and widely 

 disseminated of insect colors are those of the cuticula . . . these 

 colors develop as the cuticula hardens, and appear first, as a rule, upon 

 sclerites to which muscles are attached. In one of the earlier sections of 

 this paper I showed that the pigment develops from before backward 

 and, approximately, by segments, excepting that it may appear upon 

 the head and most posterior segments simultaneously. 



"In ontogeny color appears first, as a rule, over the muscles which 

 become active first, or upon certain sclerites of the body. These are 

 usually the head muscles, although exceptions are not infrequent. It 

 should be remembered that as the color appears the cuticula hardens, 

 and, considering that muscles must have fixed ends for their action, it 

 seems that there is a definite relation between the development of color, 

 the hardening of the cuticula, and the beginning of muscular activity; 

 the last being dependent upon the second, and, incidentally, accompanied 

 by the first. As muscular activity spreads over the animal the cuticula 

 hardens and color appears, so that color is nearly, if not wholly, seg- 

 ment ally developed. 



"The relation which exists between cuticular color and the stiffening 

 of the cuticula is thus a physiological one, the cuticula not being able to 



