COLOR AND COLORATION 2O5 



In several instances, local varieties have been artificially pro- 

 duced as results of temperature control. Thus Standfuss 

 produced in Germany, by the application of cold, individuals 

 of Vanessa urticce which were indistinguishable from the 

 northern variety polaris; and from pupa? of Vanessa cardni, 

 by warmth, a very pale form like that found in the tropics; 

 and, by cold, a dark variety similar to one found in Lapland. 



These investigators and others, notably Merrifield and 

 Fischer, have accumulated a considerable mass of experimen- 

 tal evidence, the interpretation of which is in many respects 

 difficult, involving as it does, not merely the direct effect of 

 temperature upon the organism, but also deep questions of 

 heredity, including reversion, individual variation, and the in- 

 heritance of acquired characters. 



The seasonal increase in size that is noticeable, as in C. 

 pseudargiolus and I. ajax, is doubtless an expression of in- 

 creasing metabolism due to increasing temperature. Warmth, 

 as is well known, stimulates growth, and cold has a dwarfing 

 effect. While this is true as a rule, there are some apparent 

 exceptions, however. Thus Standfuss found that some cater- 

 pillars were so much stimulated by unusual warmth that they 

 pupated before they were sufficiently fed, and gave, therefore, 

 undersized imagines. A moderate degree of warmth, how- 

 ever, undoubtedly hastens growth. 



Sexual Coloration. The sexes are often distinguished by 

 colorational as well as structural differences. Colorational 

 antigeny (this word signifying secondary sexual differences 

 of whatever sort) is most prevalent among butterflies, in 

 which it is the extreme phase of that differentiation of orna- 

 mentation for which Lepidoptera are unrivaled. 



The male of Pieris protodice (Fig. 234) has a few brown 

 spots on the front wings ; the female is checkered with brown 

 on both wings. In Colias philodice (Fig. 235) and C. enry- 

 theme the marginal black band of the front wings is sharp 

 and uninterrupted in the male, but diffuse and interrupted by 

 yellow spots in the female. In the genus Papilio the sexes 



