The Origin of the Markings of Caterpillars. 377 



eye-spots by the formation of a nucleus in the 

 " mirror," such as occurs occasionally in Deilephila 

 Euphorbia (Fig. 43), more frequently in I}. Galii, 

 and as a rule in D. Vespertilio. Nevertheless, 

 these markings arise in quite another manner to 

 the eye-spots of the Cheer ocampincz, with which 

 they conseqently have no genetic relation ; the two 

 genera became separated at a time when they 

 neither possessed spot-markings. Further, in 

 Pterogon (Enotherce we find a third kind of spot- 

 marking, which is most closely allied to the ocelli 

 of the Ch&rocampa-\&rv&,> but is situated in quite 

 another position, and must have originated in 

 another manner, and consequently quite inde- 

 pendently of these eye-spots. 



It can also be readily understood why the first 

 and second elements of the markings of the Sphin- 

 gidce should be mutually exclusive, and not the 

 second and third or the first and third. 



A light longitudinal line cutting the oblique 

 stripes, considerably diminishes that resemblance 

 to a leaf towards which the latter have a tendency, 

 and it is therefore only found in cases where an 

 adaptive marking can be of no effect on account of 

 the small size of the caterpillar, i.e. in quite young 

 stages. (See, for instance, Fig. 56, the first stage 

 of S. Populi.} At a later period of life the old 

 marking must give way to the new, and we accord- 

 ingly find that the subdorsal Jine vanishes from all 

 the segments on which oblique stripes are situated, 



