THE COLOURS OF BLUE BUTTEKFLIES. 115 



instance in which the theory of warning coloration, suggested by Mr. 

 Robinson to account for the colour of the bhie males, had failed. This 

 brought the whole question to my notice again, and I now venture 

 with much trembling to " rush in where angels fear to tread" — at least, 

 I gather from back numbers of The Entomdloi/istSbnd The Entomologist's 

 Record, that they have feared hitherto, as there is no article of any 

 kind dealing with the subject, so far as I can trace — ^and raise the 

 whole question, with our editor's permission, as a very desirable one 

 for discussion, durmg which, perhaps, some readers who have been 

 devoting their attention to raking in all the weirdest varieties, aberra- 

 tions, gynandromorphs, and other monstrosities they can get the net 

 over, rather than to finding out the why and wherefore of the differ- 

 entiated colouring of their victims, may be able to advance some 

 theories, or, at least, record some experiences, which will help some of 

 our more brainy brethren to put together a working hypothesis. 



In the introduction to vol. ii., British Noctiiae and their Varieties, 

 our editor gives (p. vi.) two tables of genetic development of pigment 

 colours as follows : (1) white, yellow, orange, red, brown, black, (2) 

 white, yellow, green, red (or brown), purple (or blue), black. Now, it 

 is remarkable that our British "blues" can show among them every 

 one of these colours, except yellow, which, I think, is not present in a 

 pure form, say gamboge or canary-yellow, in any species. From this, 

 it seems to me probable that the ancestral " blue " was more probably 

 white than blue or brown, and that the latter colours, the prevailing 

 ones nowadays, were developed by natural selection, for I do not think 

 there can be much doubt that sexual selection, from the point of view 

 of colour, is practically non-existent among butterflies, although I 

 believe it is exercised in at least one other direction ; but that is 

 another story. 



Now, according to the Darwinian theory, colours are brightest as a rule 

 in the more active sex, and duller in the other, the arrangement being- 

 turned to account by sexual selection in one case, and by protective 

 coloration the outcome of natural selection in the other ; this, of 

 course, is speaking broadly. Granting then that the bright colour of 

 the male blues is the result of great activity, and that sexual selection 

 plays no part, the two alternatives are : (1) they are blue because they 

 have reached the highest stage of development in colour, or (2) they 

 are blue because blue is a useful colour to them for protective purposes. 

 Assuming the latter is the case, then the blue is either a warning 

 colour, proclaiming their uneatableness ; or it is a mimicking colour, 

 causing them to resemble some other creature which is uneatable ; or 

 it is a protective colour in the sense that it enables them to escape 

 detection by causing them to appear similar to some inanimate object 

 when at rest temporarily with their wings open. I do not think it 

 can be a warning colour, because as a rule red or yellow, often in con- 

 junction with black, are the usual warning colours adopted by the 

 insect world, and I see no reason to believe that it is a mimicking 

 colour, because I fail to see what there is to mimic. I do think, 

 however, that it may be a protective colour in enabling the butterflies, 

 when settled with wings expanded, to resemble some blue flowers, 

 especially as they often settle on the tops of grass stems or long stalked 

 small flowers, which they entirely hide and take the place of. I also think 

 that, when flitting rapidly about, the blue colour causes a flickering effect, 



