The Origin of the Markings of Caterpillars. 183 



of six centimeters, after which the fifth moult 

 takes place, the caterpillar becoming ready for 

 pupation in the sixth stage. No striking changes 

 of colouring or marking occur after the present 

 stage, but only certain unimportant alterations, 

 which are, however, of the greatest theoretical 

 interest. 



Sixth Stage. 



In this stage the eye-like appearance of the 

 spots on the front segments becomes still more 

 distinct than in the fifth stage ; at the same time 

 these spots repeat themselves on all the other 

 segments from the fifth to the eleventh, although 

 certainly without pupils, and appearing only as 

 diffused, deep black spots, of the morphological 

 significance of which, however, there cannot be 

 the least doubt. They are situated in precisely 

 the same positions on the 5 u segments as 

 those on the third and fourth near the front, and 

 above and below the subdorsal line. A feeble 

 indication of the latter can often be recognized 



(Fig- 23). 



In all dark-brown specimens the repeated 

 spots can only be detected in a favourable light, 

 and after acquiring an intimate knowledge of the 

 caterpillar ; but in light-brown and green specimens 

 they appear very sharply defined. 



There is one other new character which I have 

 never observed at an earlier period than the sixth 



