188 PROCEEDINGS OF THE ACADEMY OF [Jail.,, 



ally present on this mark in some of the worn specimens that do not 

 now possess them. This white spot can be far more frequently 

 detected on the upper surface of ohsoleta and aixhippus than on that 

 of arthemis and probably more often than in weidermeyeri, although 

 it may attain great relative size in this species (31, PI. XXV, fig. 1). 

 Its frequent appearance in the two mimics points to an origin from 

 an ancestor of the existing North American species that was in. 

 this respect nearer in pattern to L. lorquini, in which the spot is 

 almost invariably well developed (31, 479, 480, PI. XXV, figs. 6-8). 

 At the same time the redevelopment of an ancestral feature by means 

 of mimicry must not be lost sight of as a probable interpretation. 

 The pattern of D. strigosa is such that the spot in the fore-wing cell 

 of obsoleta probably adds to the likeness, at any rate during flight.. 

 The strong development of the feature in the females — in this species 

 the more ancestral sex — favors the former hypothesis. As regards 

 the traces of the Limenitis pattern persisting in the fore- wing cell 

 on the under surface and their transference to the upper surface, 

 ohsoleta and archippns have reached nearly the same stage. The 

 most strongly marked individuals of the former are, however, more 

 ancestral, in that the white spot on the upper surface and the two> 

 spots below are larger and more conspicuous than in any examples 

 of archippus. 



The seasonal differences on the fore wing were not so well marked 

 as on the hind. Furthermore, the relationship was reversed, the 

 autumn brood being more ancestral than the spring. The difference, 

 however, was barely detectable except in one feature where it was 

 very distinct — the minute white spot in the fore-wing cell. This was 

 sharp and distinct in 11 out of 13 autumn males and only 2 out of 

 10 spring males. It was also on the whole better developed in the 

 autumn females. 



Temperature experiments on the pupa? and, if possible, on the 

 ova and larvae would be well worth trying on this form as well as on 

 archippus and floridensis. Considering what has been done by 

 Dorfmeister, Weismann, Merrifield, and Standfuss, remembering 

 also that Lamborn has recently brought evidence which suggests, 

 although it does not prove, that vestiges of "tails" can be brought 

 back to the hind wings of the tailless mimetic females of Papilio 

 dardanus (36), it is quite probable that some increase^ in the pattern 

 derived from a non-mimetic ancestor might be induced by the shock 

 of heat or cold applied to the pupal or both larval and j^upal stages.. 

 And the fact that there are certainly some seasonal differences in the 



