186 PROCEEDINGS OF THE ACADEMY OF [Jan., 



and often more strongly marked on the under surface. A trace of it 

 •could be made out on the upper surface of all the females and on 17 

 of the males; from one or both sides of the remaining males it was 

 .absent, but it is likely that when these were fresh examination with 

 -a lens would have led to the detection of a few white scales. It is 

 -clear that the trace of the original discal band is more shortened in 

 archippus than in the Arizona form, and that the 4th spot in area 3, 

 or in other individuals the 3rd in area 4, is now in the position of the 

 minute trace of a 5th spot in area 2 of obsoleta. Furthermore, the 

 l)lack discal marking retains in obsoleta more of its original appearance 

 as an outer edging to the white band than in archippus — an appear- 

 ance still more fully sustained upon the hind wing. In the fore wing 

 x)f archippus it is obviously much developed, especially at the costal 

 end, in mimicry of the model plexippus. 



The trace, on the costa itself, of the anterior end of the white band 

 of the fore wing, already described as generally to be found in archip- 

 pus (31, p. 457), was present in all the females and 19 males of 

 obsoleta, but in some of these it was barely visible. This feature is 

 apparently more often wanting altogether from archippus, but the 

 two forms have reached nearly the same level, and I think that in 

 both examination with a lens would reveal the presence of some 

 trace of the marking in most or perhaps all fresh specimens. 



I have already incidentally mentioned on p. 185 the most inter- 

 esting ancestral feature in the fore-wing pattern of obsoleta, and one 

 •entirely wanting from archippus, viz., a distinct trace in area la of 

 the inner marginal end of a white discal band like that of arthemis 

 •or weidemeyeri. This linear mark was present, varying in the 

 degree of its development, in all the females and 23 males, and 

 traces might probably have been found on all when fresh. The 

 mark is also to be found on the under surface where the fore wing is 

 overlapped by the hind, but for this reason it was only examined in 

 a few specimens; in these it did not stand out on the paler ground- 

 •color as conspicuously as on the upper surface. It has been already 

 pointed out on p. 185 that the outer end of the. mark coincides with 

 the point on the inner margin indicated by the direction of the 

 vestige of the black outer border in some individuals, viz., a point 

 well within the posterior angle of the fore wing. In a single female 

 ^Apr. 17, 1909), unfortunately rather worn, the mark in la appar- 

 >€ntly extends to the black margin at the posterior angle. The 

 same relationship to a mark stopping short of the angle is also 

 ndicated, especially in fresh specimens of the female, by a distinctly 



