COLOR AND COLORATION 1 99 



variegated coloration of lichens. Only the younger larvae, 

 however, proved to be susceptible to the colors of the environ- 

 ment ; unlike those of Amphidasis betularia, in which the older 

 larvae also were sensitive to the surrounding light. Here 

 again, natural selection is unnecessary, even if not superfluous, 

 as an explanation of this kind of protective coloration. 



Effects of Temperature. The amount of a pigment in the 

 wing of a butterfly depends in great measure upon the sur- 

 rounding temperature during the pupal stage, when the pig- 

 ments are forming. Black or brown spots have been enlarged 

 artificially by subjecting chrysalides to cold ; hence it is probable 

 that the characteristically large black spots on the under side 

 of the wings of the spring brood of our Cyaniris pseudargiolus 

 are simply a direct effect of cold upon the wintering chrysal- 

 ides. Similarly the spring brood (variety mar da} of Phy- 

 ciodes tharos owes its distinctive coloration to cold, as Ed- 

 wards has proved experimentally. Lepidoptera have been the 

 subject of very many temperature experiments, some of which 

 will be mentioned presently in the consideration of seasonal 

 coloration. 



Speaking generally, warmth (except in melanism} tends to 

 induce a brightening and cold a darkening of coloration, the 

 darkening being due to an increased amount of black or brown 

 pigment. Temperature, whether high or low, seldom if ever 

 produces new pigments, but simply alters the amount and dis- 

 tribution of pigments that are present already. 



Effects of Moisture. Very little is known as to the effects 

 of moisture upon coloration. The dark colors of insular or 

 coastal insects as contrasted with inland forms, and the pre- 

 dominance of dull or suffused species in mountainous regions 

 of high humidity, have led observers occasionally to ascribe 

 melanism and suffusion to humidity. In these cases, how- 

 -ever, the possible influence of low temperature and other fac- 

 tors must be taken into consideration. The experiments of 

 Merrifield and of Standfuss showed no effect of moisture upon 

 lepidopterous pupae. 



