152 Journal New York Entomological Society. [Voi. v. 



bl. Radial veins on primaries arising separately and five in number. 



bi2. Vein IV2 of primaries approaching cubitus MEGATHYMID.iE. 



bi2. Vein IV2 of primaries placed centrally HESPERIADv^. 



bi3. No costal vein (vein I) on primaries Pamphilin/E. 



bi3. A costal vein (vein I) on primaries Hesperin^. 



The division of the Day Butterflies rests upon the presence of a strong 

 and short downwardly curved vein at the base of primaries and joining 

 the internal margin in the Parnassi-Papilionidoe, and its absence in all 

 the other Day Butterflies. Whether we homologize this vein with the 

 loop at the base of vein VII, which we call VIII, or give it a separate 

 number the character is unaffected, for the loop runs in a contrary di- 

 rection, and the opposite development of the vein in the Swallow-tails re- 

 mains to be accounted for. But I cannot so homologize this peculiar vein 

 and for several reasons. We find in Castnia, Actias, Telea, Thyridop- 

 teryx, a lower prolongation of the loop VIII. It seemed to me at one time 

 that here might be a trace of this vein IX which would have anastomosed 

 with VIII and finally have disappeared. But the greatest encourage- 

 ment, that I might discover the phylogeny of Papilio, was offered me 

 by the drawings of Mr. Meyrick in the Geometridse. For here appeared 

 vein VIII as a degenerate (dotted in the drawings) nervure, and, be- 

 hold, IX was present likewise and indicated by a curved continuous line 

 joining internal margin as in Papilio. Here I said, can I never be mis- 

 taken. This is the internal vein of the Papilionides. But when I, my- 

 self, tried to find Mr. Meyrick's vein in nature, it was not there. The 

 pertinacity with which Mr. Meyrick repeats this vein in his drawings of 

 the Geometrid wing leads one to suspect that he has really perceived it 

 on some special occasion and now brings it in (/. e., Venilia macular id) 

 where there is no occasion. But I have small hopes. 



The general resemblances, striking as they may be between the Hes- 

 periades and Papilionides, or between Papilio and the rest of the Day 

 Butterflies, might be all developed upon another line and thp connec- 

 tion between the two would in that case be placed farther back still. 

 Any system which places the Papilionides between the groups of the 

 other Day Butterflies, all of which appear to me to hang more or less 

 closely together, must first account for the fundamental neurational 

 differences before it can be entitled to credit. The diurnal habit might 

 be set down, with other features, to convergence. 



There are two chief directions in which changes are making in the 

 structure of the butterfly wing. The first is traceable throughout the 

 order. Its aim is the breaking up of the system of theMedia, one 



