216 Mil. E. B. POULTON ON THE PROTECTIVE [Mar. I, 



Darwin's which enables us to point towards the purely sexual value 

 of one factor in the appearance of certain butterflies ; and by the 

 same kind of observation it is likely that increasing stability will 

 be given to tlie whole theory of sexual selection. Darwin noticed 

 that the magnificent surface-colours which exist on many tropical 

 butterflies, and which change with the position from which the 

 insect is observed {being probably due to diffraction), become 

 most brilliant when they are seen from the front, and at an angle 

 which corresponds with that at which they would be seen by the 

 female as the male butterfly approaches her. 



As a further test of the " warning " value of certain colours, we 

 can use as a comparison the colours and patterns of certain larvae 

 which are known to be "warning" only, or which at any rate cannot 

 be sexual. After giving the list and the experimental details, I 

 shall attempt to show that there are certain combinations of colour, 

 and sometimes even certain patterns, which are generally distinctive 

 of "warning" as apart from sexual coloration. And such dif- 

 ferences of type are to be expected ; for the two systems of coloration 

 appeal to a different class of animals and appeal to a different 

 sense. The " warning " colours of insects appeal to a Vertebrate' s 

 sense of what is conspicuous ; the sexual colours appeal to an 

 Invertebrate's sense of what is beautiful. And it is one of the 

 most remarkable facts in the study of comparative psychology 

 that our own sense of what is beautiful entirely coincides with that 

 of an insect, so that the difference in the two types of coloration 

 depends entirely upon the sense alluded to above, and has probably 

 no reference to the class of animals in which the sense exists. 

 For, if we had no knowledge of tiie use and meaning of the colours 

 of insects, we should all agree in maintaining that certain colours 

 and patterns (whicli we now trace to the action of sexual selection) 

 comprise all that is beautiful in the appearance of this class of 

 animals, and we should draw a sharp line between these and 

 other combinations of colour which we now recognize as possessing 

 an entirely different significance. 



In the following instances it is unnecessary to enter upon any 

 preliminary account, as the table contains all the details which 

 I can find recorded. Of course this list must contain any cases 

 (if tested) in which a conspicuous appearance is believed to be 

 due to " mimetic " resemblance to another species protected by 

 possessing some unpleasant attribute. I much regret that hardly 

 any of these most interesting cases have been used for experiment 

 (see Table IV., pp. '218-223). 



Looking at this fourth table, we find that the theory of warning 

 colours is again confirmed in the most marked manner. Unfortu- 

 nately the extremely interesting " mimetic " cases still lack the 

 necessary experimental demonstration; although the intimidating 

 larvae of C. elpenor and C. vinula are really mimetic of vertebrate 

 appearances, and the former has been shown to be attended by a 

 considerable amount of success. The only "mimetic" form in 

 this last list is Sesia fuciformis, and in this case the mimicry is 



