3 1 2 Studies in the Theory of Descent. 



Besides the larvae of the Micro-lepidoptera and 

 of those species living in the dark, there is also a 

 complete absence of marking in the young stages 

 of many caterpillars. Thus, all the Sphingidce of 

 which I have been able to observe the develop- 

 ment, show no markings immediately after emer- 

 gence from the egg ; in many they appear very 

 soon, even before the first moult, and, in other 

 species, after this period. 



2. The second category of markings, longitudinal 

 stripes, is very widely distributed among the most 

 diverse families. This character is found among 

 the larvae of butterflies, Sphingidcz, Noctucz } Micro- 

 lepidoptera, &c., but in all these groups it is absent 

 in many species. This last fact is opposed to the 

 view that this character is purely morphological, 

 and leads to the supposition that it may have a 

 biological value, being of service for the preserva- 

 tion of the individual, and therefore of the 

 species. 



I find that such marking is of service, stripes 

 extending longitudinally along the upper surface 

 of the caterpillar generally making the latter less 

 conspicuous. This, of course, does not hold good 

 under all circumstances, since there are many 

 species with very striking colours which possesss 

 longitudinal stripes. Let us consider, however, a 

 case of adaptive colouring, such as a green cater- 

 pillar, which, on this account only, is difficult to 

 see, since it accords with the colour of the plant 



