208 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 1s a pure assumpticn, in the case of insects, 
and one that is inadequate in spite of its plausibility, for (1) 
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. promcethea, 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) ‘1s 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 
