2 1 4 Studies in the Theory of Descent. 



the twenty-five mentioned, and I only know this 

 variety from single individuals, found at a former 

 period. Among the twenty-five caterpillars., all 

 gradations of colour occurred, from pitchy black to 

 light clay-yellow, and even to an almost whitish- 

 yellow ; some were brownish-black, others of a 

 beautiful chestnut-brown, and others yellowish 

 brown, dark clay-yellow, or brownish-red. Out 

 of twenty-one specimens of which the ground- 

 colours were noted, there were nine black, nine 

 clay-yellow, and three brown ; each of the three 

 groups again showing various minor modifications 

 of colour. The other colours also varied some- 

 what. Thus, the " mirrors " were sometimes 

 white, sometimes strong yellow, and occasionally 

 they also contained a reddish nucleus. 



The variations in the shagreening were espe- 

 cially interesting, inasmuch as these appeared 

 to have a striking connection with the general 

 colouring of the caterpillar. Black specimens 

 seldom show such sparse shagreening as that 

 represented in PI. V., Fig. -46, but are generally 

 thickly scattered with large shagreen-dots right up 

 to the dorsal line (Fig. 47, PI. VI.), then strikingly 

 resembling the adult larva of D. Euphorbia. The 

 light ochreous-yellow individuals, on the other 

 hand, were sometimes entirely without shagreen- 

 ing (Fig. 48, PI. VI.), being smooth, and much 

 resembling the light ochreous-yellow or yellowish- 

 red caterpillar of D. Niccza (Fig. 51, PI. VI.). 



