422 Studies in tJie Theory of Descent. 



black maintaining its ground longer in the Italian 

 than in the German form. 



In the Genoese form the two first stages are 

 completely black, and in the third stage an orange- 

 yellow lateral stripe first appears. I n the German 

 form this stripe appears in the second stage, and 

 there is not subsequently added, at least on the 

 middle segments, a yellow border surrounding 

 some of the warts of the median series. In the 

 third stage, however, the yellow (which is but the 

 precursor of the later green colour) becomes 

 further extended, so that the caterpillars often 

 appear of an orange colour, some or all of the 

 warts and certain spots and stripes only being 

 black (Figs. 66 and 68). The warts are also 

 often yellow while the ground remains in most 

 part black in brief, the bright colour is in full 

 struggle with the black, and an endless series of 

 variations is the result of this conflict, whilst in the 

 corresponding stage of the Genoese form almost 

 complete constancy prevails. 



This constancy remains also in the following 

 (fourth) stage, the caterpillar still being deep 

 black, only the yellow (sulphur-coloured) lateral 

 stripe, which has now become brighter, indicating 

 the impending change (Fig. 67). This takes 

 place in the fifth stage, in which the ground- 

 colour suddenly becomes bright green, the black 

 remaining at most only in traces on the anterior 

 edges of the segments. 



