CHEMiSTEY OF INSECT COLOUitS. 135 



antiopa the blue was least resistent to the reagents ; there is of 

 course, as already explained, nothing contradictory in a physical 

 colour thus disappearing. I have included in this group the 

 crescent-shaped blue marks on P. polyctor, since the behaviour 

 of these strongly recalled that of the Vanessidse, especially V. io. 

 It is especially to be noted that this blue also returned in a 

 few days.* 



And now, in conclusion, we come to the group of Lyccena. I 

 do not know what to say about these species. They are the only 

 blues I know of which are not certainly physical. At one time I 

 thought it highly probable that these were, anyhow, pigment 

 colours ; but further reflection and experience have considerably 

 modified my views. On the one hand, there were obtained in each 

 species colour changes, chiefly to a slate colour or grey, that I at 

 one time thought pretty good evidence for a pigment ; but, in the 

 light of later work, this conclusion seems tome much shaken. Here, 

 again, we are arguing so much in the dark, being left without any 

 clear answer, such as would be given by either a " solution " or a 

 " reversible " effect. As against the supposition that there is any 

 pigment here, we must set the facts that in corydon, at any rate, the 

 blue is suspiciously metallic in appearance ; while the same remark 

 applies to many specimens of the female of alexis — such species, I 

 mean, as are in the intermediate stage of colouring, between the 

 brown of the normal female and the full blue of the male. In ad- 

 dition, I would draw attention to the facts that, as recorded in my 

 original tables,t the blue in several instances acquired a greenish 

 tint. This appears to me, now, very suspicious, and somewhat 

 indicative of a physical blue ; but since no undoubted pigment 

 blue has yet been found, it is, of course, impossible to assert that 

 such would not become green under the influence of reagents. 

 On the whole, then, pending the appearance of fresh evidence, it 

 seems to me that all we are justified in asserting of LyccBna-hlne 

 is that it is, anyhow, somewhat different in character from any of 

 the other blues. This much seems clearly shown by its reactions ; 

 but whether it be a physical or chemical colour we cannot at 

 present decide. 



J. 



Having thus examined in turn the evidence yielded by the 

 reactions of each of the various colours, it only remains briefly to 

 sum up the results, before passing on to the few remarks that 

 have to be made on the biological aspect of these experiments. 

 At the same time I may also take the opportunity to make one or 

 two corrections and additions to previous statements. 



* It was very difiScult to know how to describe the reaction of this species. I 

 have entered the change as that to a " sort of yellow," on account of the appearance 

 of the traces whence the blue had temporarily disappeared. But it must not for a 

 moment be supposed that there was here any question of an actual chemical change 

 to yellow. 



t Entom. xxiii. 252. 



