3 1 4 Studies in the Theory of Descent. 



It has already been mentioned that the smallest 

 species are devoid of longitudinal striping. The 

 larvae of the Micro-lepidoptera show no such 

 marking, even when they do not live in the dark, 

 but feed either on the surface or in superficial 

 galleries of the leaves (Nepticula, &c.), in which 

 they must be exposed to almost as much light as 

 when living on the surface. The fact that the 

 subdorsal line sometimes appears in very young 

 Sphinx-larvae is explained, as has already been 

 shown, by the gradual backward transference of 

 adaptational characters acquired in the last stage 

 of development. 



It can easily be demonstrated that longitudinally 

 striped caterpillars mostly live on plants, of which 

 the general appearance gives the impression of a 

 striped arrangement. We have only to consider 

 in connection with their mode of life, any large 

 group of adaptively coloured species marked in 

 this manner. Thus, among the butterflies, nearly 

 all the Satyrincz possess larvae conspicuously 

 striped a fact which is readily explicable, because 

 all these caterpillars live on grasses. This is the 

 case with the genera Melanargia, Erebia^ Satyrus, 

 Pararge, Epinephele, and Ccenonympha, no species 

 of which, so far as the larvae are known, is without 

 longitudinal stripes, and all of which feed on 

 grasses. It is interesting that here also, as in 

 certain Sphingida, some species are brown, i. e., 

 adapted to the soil, whilst the majority are green, 



