MELANISM AND MELANOCHROISM. 297 



and wings thinner and purer white than spring form. P. rapie, 

 ' Further south (in the United States) the winter (spring) form 

 tends to pure white on the upper surface' (G. H. French). 

 Colias euiytheme, spring form keeivaydin, Edw., smaller than 

 summer form, duller yellow and with less roseate reflection, 

 both sides more sprinkled with black scales, the orange patch 

 on the fore wings not so marked, sometimes almost absent. 

 PItyciodes tharos, seasonal forms niarcia, Edw., and morpheus^ 

 Fb. ; P . phaon also has seasonal forms. Grapta interroi^ationis, 

 hybernating ioruifabricii, Edw., summer form umbrosa, Lintn.; 

 ' There are about four broods in a season, and while those of 

 the last or hybernating brood are the pale forms, the others 

 are more or less mixed, as Mr. Edwards has shown ' (G. H. 

 French). G. comma, hybernating form Juxrrisii, Edw., summer 

 form dryas, Edw. Lyccena pseudargiolus vars. lucia, Kirby, and 

 mavginata, Edw., coming from pupae which have hybernated, 

 show coalescence of markings on the under side of the hind 

 wings. Seknia bilunaria var. juliaria, Haw., and vS. limaria 

 var. delunaria, Hb. In North America, owing to the great 

 difference between the summer and winter climates, seasonal 

 forms are often very marked. As a rule, the spring form, 

 emerging from pupse which have hybernated, is smaller and 

 darker than the summer brood, a condition which has been 

 attributed to the effects of cold while in the pupa stage. But, 

 strangely enough, a moderate amount of cold appears to have 

 an opposite effect, for in our climate the spring Pieridce, which 

 are dark in America, are distinctly lighter than the summer 

 forms, and the imported P. rapcB would seem to have retained 

 that character somewhat in America. Also, as regards size, I 

 believe that it is found that the races of large silk-moths, 

 which are bred on the cooler slopes of the Himalayas, are 

 invariably larger and finer than those of the same species from 

 the heated plains of India ; and this has been attributed to 

 their longer sojourn in the pupal ^ state, whereby they have 

 more time for development. The only theory I can advance 

 to harmonise these various facts may seem to many a some- 

 what unwarranted one, and I shall look with interest for any 

 comments on it. The darker and smaller forms may be 

 supposed always to be those whose development has been 

 quick, the metabolism great in proportion to the growth, while 



' I should cuii-,i(lci- it iiiiiiossiblc lluii a longer sc)joarn in the pujial state, cuuhl 

 make them " larger and liner." One can understand that a longer sojourn in the 

 larval state, with plenty of food, would act in this direction. — ^J.W.T, 



