significance of wing -markings. 101 



but and y are nearly always blue, or at least edged 

 with blue, in P. luuitcra and P. myrinna. 



These cases would seem to support the suggestion 

 already made that the " blue shade " in F. io represents 

 an encroachment inwards of the blue of the centres of 

 the submarginal series of spots.* 



The question now arises whether we can trace the 

 origin of this series of blue-centred spots, which we 

 have seen in their full development and in their decline. 

 It will be understood how keenly, when I was investi- 

 gating this point, I sought among the Fritillaries for 

 some indication of this blue-centred black border. Did 

 there exist any species of Argynnis with blue round the 

 margins of the wings ? The clue to the solution of the 

 question was supplied by the same species that is of so 

 much interest in regard to the series D, a — ^, viz., 

 A. niphe. In this insect we are at once struck by the 

 resemblance of the hind wing, both in <? and ? , to that 

 of P. cardui. The various series of dark markings are 

 seen to correspond, spot for spot, and what is more 

 interesting still, the submarginal portion of the wing 

 shows a blue colour, best developed near the anal angle, 

 which at once suggests the remnants of blue in P. cardui. 

 The blue here does not, it is true, occupy the centres of 

 the dark spots corresponding to those which form the sub- 

 marginal series in P. cardui, but rather belongs to the 

 ground colour between this series and one still further out, 

 while externally comes another interrupted narrow area 

 of blue ground colour before the black edge of the wing is 

 finally reached. Still it is difiicult to resist the conclusion 

 that the blue in P. cardui is derived from a source indicated 

 by the same colour in A. niphe, wdiich indeed may have 

 been effected by a spreading inward of the blue in ^ the 

 form of a shade which has afterwards been cut ofl:', of 

 which we have already seen an example in A. prorsa, or 

 by the taking up of the outer row of dark spots in an 

 attenuated form to make with the submarginal row a 

 series of composite spots, the included blue ground 

 colour becoming the centres of the series so made. This 



" A similar extension inwards of bluish coloration from the 

 series of blue-centred sj^ots occurs on the under side of A. ley ana, 

 both upper and lower wing. In A. prorsa (hind wing) this has 

 become separated from the border, remaining as a small but 

 distinct bluish patch. 



