534 Appendix. 



of phytophagic variations must therefore have been still 

 less perceptible than the now perfected final results; and 

 this leads to the conclusion that minute variations of 

 this character were of sufficient importance to pro- 

 tectively-coloured species to be taken advantage of by 

 natural selection. But minute variations in a dull- 

 coloured larva would, as' previously pointed out, produce 

 a comparatively much greater effect than such variations 

 in a brilliantly-coloured species ; and as protection is 

 required by the former, the initial phytophagic effects 

 would be accumulated, and the power of adaptability 

 conferred by the continued action of natural selection, 

 whilst in vividly-coloured species where no power of 

 adaptability is required this cause of variation would not 

 only produce a result which, as compared with its effects 

 upon dull species, may be regarded as a "vanishing 

 quantity," but this result would be too insignificant to 

 be taken advantage of by natural selection, which is in 

 these cases dealing only with large " quantities," and 

 striving to make the caterpillars as brilliant as possible. 

 The fact that vividly-coloured distasteful larvae do not 

 show phytophagic variation is to my mind explained 

 proximately by these considerations ; the ultimate cause 

 of phytophagic variability regarded as a chemico-physio- 

 logical action requires further investigation. 



Sexual Variation in Larva. Since most of the mark- 

 ings of caterpillars can be explained by the two factors 

 of adaptation and inheritance, or, in other words, by their 

 present and past relations to the environment, and since 

 sexual selection can have played no direct part in pro- 

 ducing these colours and markings, I feel bound to re- 

 cord here some few observations on the sexual differ- 

 ences in larvae in addition to the cases of Anapcea and 

 Orgyia already recorded (note i., p. 308) and of 

 Lophostethus Dumolinii (p. 527). 



