1142 JOURNAL, BOMBAY NATURAL HIST. SOCIETY, Vol. XXI, 



-consequences of the dispersal of individuals thus eflFected leads to the 

 breaking down of distinctions between local races thus preventing varia- 

 tion in the insects of widely separated districts. These migrating Pieridce 

 are all very strong fliers and some individuals would doubtless go far from 

 their place of origin ; in the course of a few years, probably hundreds of 

 miles. 



The larevailing colouring is, as already stated, white, often suffused with 

 some shade of yellow above as well as below, the upperside often with 

 black bordering which is subject to variation in extent and intensity ac- 

 cording to the season, sometimes, indeed, afl^ecting very nearly the whole 

 surface in the so-called wet-season broods where the dry-season individuals 

 are lightly marked. In certain genera (Colotis) we get species that are 

 salmon-coloured, in others ( Colotis^ Hebomoia, Lvias) the apex of the f orewing 

 in some species has an orange or yellow or carmine patch; in Prioneris 

 and Delias the underside of the hindwing may have a broad red terminal 

 border or basal red spots ; Pareronia has in the male some shade of light blue 

 with black veining and border on the upperside ; in Appias the underside 

 in certain species is subject to suffusion with deep yellow while Terias is 

 always some shade of yellow above and below. Fresh young shoots that 

 appear in the hot weather in India produce large specimens with extensive, 

 intense black markings while the comparatively hard, dry leaves of the 

 cold weather result in smaller and much lighter insects. Now, in the 

 generality of cases, dry, hard leaves mean slow feeding, consequently slow 

 lar/al growth and large, light specimens ; new, tender leaves have 

 the effect of allowing quicker growth, producing smaller, darker individuals. 

 In the Pieridoe, seemingly, the rate of growth of the larva is more or less 

 •constant whatever the quality of the food available and, therfore, the more 

 food and the easier it is to assimilate, the larger the resulting imagine is. 

 All the larvae of the family are voracious eaters and feed upon soft-leafed 

 trees and bushes or upon herbaceous plants the young shoots of which are 

 fast growing and very juicy ; the soft leaves admit of the quantity of food 

 being always sufficiently easily assimilable to produce the normal growth 

 and the great softness of the new shoots gives an extra impetus to increasing 

 the size, while their extreme juiciness produces the exuberance of black 

 pigment which is so remarkable in the family. The colouration of the 

 wings is characteristic at all seasons and its style never varies though 

 the extent may ; even on the undersides the style is constant and there 

 is nothing ever to be found of the curious seasonal dimorphism existing in 

 some hympaline and satyrine butterflies. The shapes of the wings are 

 the same at all seasons, also though, perhaps, Terias losta has the apex of 

 the forewing more produced in the cold weather. 



The larger whites are very strong, fast fliers and progress in the skipping 

 .style, in successive vmdulations, Hebomoia, Catopsilia ; Delias, however 



