The Origin of the Markings af Caterpillars. 205 



Fourth Stage. 



The third moult, which again occurs after four 

 days, is not accompanied by such important 

 changes. The green ground-colour has now 

 completely disappeared, and is replaced by a dull 

 black. The caterpillars are now, as also in the 

 previous stage, extremely variable. Thus, for 

 example, a triangular patch of the green ground- 

 colour may be retained on the posterior edge of 

 the segments (Fig. 41), those specimens which 

 possess this character generally having their mark- 

 ings retarded in development, as shown by the 

 absence of the second " mirror " of the ring-spots. 



In Fig. 41 the shagreen-dots from which 

 this second " mirror" is subsequently formed, 

 are distinctly larger than the others, and on the 

 eleventh segment two of them have already 

 coalesced. 



Fifth Stage. 



After another period of four days, the fourth 

 moult takes place. The marking remains the same, 

 but the colours become more vivid; the brick-red of 

 the head, horn, dorsal line and legs, changing into 

 a fiery red. The spiracular line, formerly green 

 alternating with yellow, generally becomes re- 

 solved into a row of reddish-yellow spots. Ten 

 days later the caterpillar (8*5 centimeters in 

 length), ceases to feed, and prepares for pupation. 



