35 Studied in the Theory of Descent. 



equally due to heredity. Thus, it is quite possible 

 that the faint and inconspicuous ring-spots of Deile- 

 phila Vespertilio are now valueless to the life of 

 the species they may be derived from an ances- 

 tral form, and have not been eliminated by natural 

 selection simply because they are harmless. I 

 only mention this as a hypothetical case. 



In the case of markings of the second class, 

 i.e. oblique stripes, a transference to later phyletic 

 stages can be demonstrated, although the stripes 

 thereby lose their original biological value. Thus, 

 the Chcerocampa larvae, when they were green 

 throughout their whole life and adapted to the 

 leaves, appear to have all possessed light oblique 

 stripes in imitation of the leaf-ribs. All the species 

 of the older type of colouring and marking, such 

 as Chcerocampa Syriaca (Fig. 29) and Darapsa 

 Chcerilus (Fig. 34), and also the light green young 

 forms of C. Elpenor (Fig. 20), and Porcellus 

 (Figs. 25 and 26), show these oblique stripes. In 

 these last species the foliage imitation is abandoned 

 at a later stage, and a dark brown, or blackish 

 brown, ground-colour acquired. Nevertheless the 

 oblique stripes do not disappear, but show them- 

 selves in the fourth stage especially, and sometimes 

 in the fifth as distinct dirty yellow stripes, although 

 not so sharply defined as in the earlier stages. 

 These persistent stripes, in accordance with their 

 small biological value, are very variable, since 

 they are only useful in so far as they help to break 



