172 ENTOMOLOGY 



harden without becoming yellow or brown. What bearing has this 

 upon the origin of color patterns? In the lower forms of tracheates, 

 such as the Myriapods, colors appear as segmental repetitions of spots 

 or pigmented areas which mark either important sclerites or muscle 

 attachments. On the abdomens of insects, where segmentation is best 

 observed, color appears as well-defined, segmentally arranged spots, 

 but on the thorax segmentation is obscured 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, corresponding 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. 



"So firmly have these characters become ingrained in the tracheate 

 series, and so important is this relation of the hardening of the cuticula 

 to the musculature and to the formation of body sclerites, that even the 

 most specialized forms show this primitive system of coloration; and, 

 although there may be spots and markings which have no connection 

 with it, still the chief color areas are thus closely associated." 



Development of Color Patterns. Although the causes of colora- 

 tion are, for the most part, obscure, it is possible, nevertheless, to point 

 out certain paths along which coloration appears to have developed. 

 These paths have been determined by the comparison of color patterns 

 in kindred groups of insects and the study of colorational variations in 

 adults of the same species. The development of coloration in the in- 

 dividual, however, has as yet received but little attention excepting 

 the excellent studies of Mayer and of Tower. Butterflies, moths and 

 beetles have naturally been preferred by most students of the subject. 



The most primitive colors among moths are uniform dull yellows, 

 browns and drabs the same colors that the pupal blood assumes when 

 it is dried in the air. These simple colors prevail on the hind wings of 

 most moths and on the less exposed parts of the wings of highly colored 

 butterflies. The hind wings of moths are, as a rule, more primitively 

 colored than the front ones because, as Scudder says, "all differentiation 

 in coloring has been greatly retarded by their almost universal conceal- 

 ment by day beneath the overlapping front wings." Exceptions to 

 this statement are found in Geometridae and such other moths as rest 



