265 Studies in the Theory of Descent. 



the head is light green, with two narrow blackish 

 brown lines surrounding the clypeus ; the horn 

 and thoracic legs are black ; claspers, reddish 

 green ; length, twelve to thirteen millimeters. 

 (Fig- 540 



Third Stage. 



After another period of four days the second 

 moult occurs, neither colour nor marking being 

 thereby affected. Only the horn, now no longer 

 forked, becomes brownish with a black tip. The 

 young caterpillars are now, as before, admirably 

 adapted to the pine needles, on which they feed 

 by day, and from which they can only be distin- 

 guished with difficulty. 



Fourth Stage. 



The third moult also brings no essential change. 

 The ground-colour and marking remain the same, 

 only the spiracles, which were formerly dull yellow- 

 ish, are now of a vivid brick-red. The horn be- 

 comes yellowish-red at the base. 



Fifth Stage. 



The marking is only completely changed in the 

 fifth and last stage. A broad reddish-brown dorsal 

 line replaces the subdorsal, more or less completely. 

 The supra-spiracular line also becomes broken up 

 into numerous short lengths, whilst the green 

 ground-colour in some specimens becomes more or 



