2O8 ENTOMOLOGY 



to be immune from the attacks of birds as described beyond. 

 In this way, as Wallace suggests, the egg-laden females may 

 escape destruction, as they sluggishly seek the proper plants 

 upon which to lay their eggs. Here would be a fair field for 

 the operation of natural selection. 



In most insects, however, sexual differences in coloration 

 are apparently of no protective value and are usually so trivial 

 and variable as probably to be of no use for recognition pur- 

 poses. The usual statement that these differences facilitate 

 sexual recognition is a pure assumption, in the case of insects, 

 .and one that is inadequate in spite of its plausibility, for ( i ) 

 it is extremely improbable from our present knowledge 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 unneces- 

 sary, to say the least, for sexual recognition. Thus, notwith- 

 standing the marked dissimilarity of coloration 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 am- 

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



Hence, when useless, colorational antigeny cannot have 

 been developed 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 Coleop- 

 tera, finds that each of the black spots on the pronotum of the 

 Colorado potato beetle (Fig. 237) " is developed in connection 

 with a muscle, and marks the point of attachment of its fibers to 

 the cuticula." Thus the color pattern, in its origin, is not neces- 

 sarily useful. This point is so important that we quote Tow- 

 er'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 



