Phyletic Parallelism in Metamorphic Species. 471 



They appear most distinctly in the groups com- 

 posed of families. 



Nobody has as yet been able to establish the 

 group Rhopalocera by means of any single cha- 

 racter common to the larvae ; nevertheless, this 

 group in the imagines is the sharpest and best 

 defined of the whole order. If we inform the 

 merest tyro that clubbed antennae are the chief 

 character of the butterflies, he will never hesitate 

 in assigning one of these insects to its correct 

 group. Such a typical character, common to all 

 families, is, however, absent in the larvae ; and it 

 might be correctly said that there were no Rho- 

 palocerous larvae, or rather that there were only 

 larvae olEquites, Nymphales, and Heliconii. The 

 larvae of the various families can be readily sepa- 

 rated by means of characteristic distinctions, and 

 it would not be difficult for an adept to distinguish 

 to this extent in single cases a Rhopalocerous 

 caterpillar as such ; but these larvae possess only 

 Jamily characters, and not those of a higher 

 order. 



This incongruence partly depends upon the cir- 

 cumstance that the form-divergence between a 

 Rhopalocerous and a Heterocerous family is much 

 greater on the side of the imagines than on that of 

 the larvae. Were there but a single family of 

 butterflies in existence, such as the Eguites, we 

 should be obliged to elevate this to the rank of 



O 



a sub-order on the side of the imagines, but not on 



