COLOR AND COLORATION 209 



one of the earlier sections of this paper I showed that the pig- 

 ment 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 hard- 

 ening 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, segmentally developed. 



" The relation which exists between cuticular color and the 

 stiffening of the cuticula is thus a physiological one, the cutic- 

 ula not being able to harden without becoming yellow or 

 brown. What bearing has this upon the origin of color pat- 

 terns? In the lower forms of tracheates, such as the Myria- 

 pods, colors appear as segmental repetitions of spots or pig- 

 mented areas which mark either important sclerites or muscle 

 attachments. On the abdomens of insects, where segmenta- 

 tion is best observed, color appears as well-defined, segmen- 

 tally arranged spots, but on the thorax segmentation is ob- 

 scured and lost upon the head. Of what importance, then, is 

 pigmentation? And how did it arise? If the ontogenetic 

 stages offer any basis for phylogenetic generalization, we may 

 conclude that cuticula color originated in connection with the 

 hardening of the integument of the ancestral tracheates as 

 necessary to the muscular activity of terrestrial life. The 

 primitive colors were yellows, browns and blacks, correspond- 

 ing well with the surroundings in which the first terrestrial 

 insects are supposed to have lived. The color pattern was a 

 segmental one, showing repetition of the same spots upon suc- 

 cessive segments, as upon the abdomen of Coleoptera. 

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