120 Br. F. A. l)ixey on the iihylogcnetic 



spots between the lighter patches. This, as we have 

 seen, is exactly the state of things now existing in 

 A. diana $ ; and a consideration of this and other 

 species {A. idalia, A. leto, &c.) will lead us to the con- 

 clusion that the process of differentiation began at the 

 hind border of the wings, and has gradually extended 

 inwards towards the body. Thus in A. diana ? , we find 

 the series of dark spots IV. and III. already distin- 

 guishable, though not yet well-defined, while [I. is just 

 emerging into separate existence.* 



The four normal series of dark marks having thus 

 been made distinct, as, for instance, in A. paphia var. 

 calcsina, we find in the next place a very general altera- 

 tion in the pale areas of the ground colour between the 

 spots. This loses its dull olive or bluish tint and 

 becomes bright brown, as in nearly all Argynnids, the 

 spots at the same time becoming, as a rule, smaller and 

 more sharply defined. The original ground colour, 

 however, clings to the females of certain species, and 

 even, though in a less degree, to the males. Among the 

 female Argynnids which retain the primitive ground 

 colour, there occurs the very striking form A. sagana, in 



-'■ Scudder (oj)- cit., vol. i., pp. 513 — 515) advances the view that 

 the dark coloration in butterliies began as a dark border to the 

 wings, spreading inwards and breaking up. It does not appear 

 from the passage cited whetlier Scudder would consider the spots 

 in the Argynnids to have directly arisen in this way, thoiigh his 

 language would seem to suggest such a conclusion. I myself 

 believe the balance of probability to be in favour of the view taken 

 in the text, for the following reasons : — (1). Other evidence seems 

 to show that the darker Argynnids are the older. (2). The general 

 prevalence of a dark colour at the base of the wings even in brown 

 Argynnids indicates that this at least is an ancient feature. {S). 

 The spots in series II. seem by their shape {vid. p. 116, note) to bear 

 traces of their latter differentiation. Such species as A. lathonia, 

 in which the spots of series II. are distinct and circumscribed, like 

 those of series III., we should on other grounds consider as the 

 more highly specialised members of their group. Higgins (" On 

 the Colour-patterns of Butterflies," ' Journal of Science,' 1868, 

 pp. 323 — 329), suggests that the arrangement of the dark markings 

 depends on that of the nervures, from the immediate neighbourhood 

 of which they appear always to take their rise ; while the lighter 

 ground colour of the wing, which may be more or less affected by 

 a " blush," is independent of the nervures. He makes, however, 

 no attempt to show any reason for the alleged couuection between 

 nerviires and dark colom'ing. As a matter of fact, both kinds of 

 markings, whether light or dark, may either follow the nervures 

 or be independent of them. 



