1900.] GROTE—THE DESCENT OF THE PIERIDS. 65 
EXPLANATION OF PLATE II. 
The figures are obtained by an improved photo-lithographic pro- 
cess. 1S'==subeostal; “'—sadtus 1'to 53 17 media ‘to 35 
C=cubitus1 to 2; 4 —analtrto 3. The first anal vein is obso- 
lete ; the thin fork to second anal is not numbered. On hind 
wings h, s. = humeral spur. 
Fig. 7. Pieris napi. Note the Pierine and original position of R1 and 2 above 
the cell; though here 72 is advanced nearly to cross-vein, and in this is P. xapz 
a slightly more specialized form than the type of the genus ?. rage, as also in 
that the fork 73 is still more reduced. On hind wings h. s. abbreviate, curving 
outwardly, The fork to second anal on fore wings is thin, but apparently a func- 
tional vein. Compare Schm. Hild. Taf. I, Fig. 5, for figure of P. ape. 
Fig. 8. Alesapia peloria. Type of genus, belonging to the opaque-veined 
Aporia series. When compared with P%erzs, more generalized, the fork of #3 
being longer. Consult the figure of Aforia, cited in text, for comparative details. 
Fig. 9. Mylothris rhodope. Type of genus; a four-branched form belonging 
to the Ascza series; AI and #2 in the original Pierine position above the cell; 
the veinlet 3 is slightly bent just below costa (as in Mancifium), showing 
that an additional radial veinlet has shortly been given up. 
Fig, 10, Llodina egnatia 2. Type of genus; belongs to the clear-veined, 
thin and wide-winged Ascza group, convergent with Prerzs. The most special- 
ized form, as shown by the radius, being three-branched, and A2 advanced 
beyond cross-vein. Compare text. 
Fig. 11. Phrissura egis 9. Type of genus; a more generalized form than 
Elodina, as shown bythe four-branched radius; #2 not advanced as far as 
the cross-vein, still in the Pierine position. Compare, for these points, with 
preceding figure. 
Fig. 12. Wepheronia poppea (idotea). Type of genus. This is the general- 
ized form of AZylothris (Fig. 9), and in which the radius is five-branched. 2 
is further from cross-vein than in the more specialized My/othris, of which this is 
probably the direct ancestral form. The shape of primaries is different from 
Mylothris, the pattern identical, The fork to second anal is here very thin and 
perhaps hardly functional. 
Fig. 13. Zrifurcula huanco §\. The primary wing shows the 77ifurcula 
position of #2, advanced to just opposite the cross-vein. Compare text. 
PROC. AMER, PHILOS. SOC. XXxtx. 161. E PRINTED APRIL 16, 1900. 
