246 Studies in the Theory of Descent. 



First Stage. 



After about eight days the caterpillars emerge. 

 They are only two millimeters in length, and are at 

 first yellowish, but soon become green, set with small 

 single bristles, and they possess a short greenish 

 caudal horn, which afterwards becomes black. 

 The head is greenish-yellow. The young larvae 

 are entirely destitute of marking. (PL III., 

 Fig. i). 



Second Stage. 



The first moult takes place after four days, the 

 caterpillar now acquiring the marking which it 

 essentially retains to pupation. 



Fine white subdorsal and spiracular lines ap- 

 pear, and at the same time a dark green dorsal 

 line, which, however, does not arise from the de- 

 position of pigment, as is generally the case, but 

 from a division in the folds of the fatty tissue along 

 this position. (Fig. 2, PL III.) 



The colour is now dirty green in all specimens, 

 the skin being finely shagreened. 



Third Stage. 



The second moult, occurring after another 

 period of four days, does not bring any change of 



successively, the moth then hovering over and sucking at the 

 flowers for some time. The eggs exactly resemble in colour 

 the young green buds of Galium. 



