1900.] GROTE—THE DESCENT OF THE PIERIDS. 5 67 
EXPLANATION OF PLATE IV. 
The figures are obtained by an improved photographic process. 
S = subcostal vein; the costal vein is absent through reduction in 
the Lepidoptera ; A radius 1 to5; 1/—mediar to 3; C==cu- 
bitus r to 2; A—analrto 3. On secondaries h. s. = humeral 
spur. The thin fork to second anal of primaries at base is not 
numbered. 
Fig. 20. Midea genutia. Type of genus. A four-branched Anthocharid, in 
which #2 has just passed out of the 77ifurcula position opposite cross-vein. 
Compare with Zetracharis, in which £2 has not reached the cross-vein. 
Fig. 21. Zegris eupheme. Type of genus. A five-branched Anthocharid, in 
which #2 has just passed the 77zfurcu/a position. A more generalized form 
than Midea. 
Fig. 22, Lroessa chilensis. Type of genus. One of the most generalized Pierids, 
ancestral tothe Anthocharid line. Radius five-branched; £2 in original position 
above the cell and close to A1, which latter branchlet alone always remains con- 
stant in position and does not shift. The first median branchlet, which in all 
other Anthocharid genera has ascended radius and springs from it outside of cell, 
here retains its primitive position on cross-vein. This rare type is most instruc- 
tive in supplying a generalized stage, rendering the succeeding steps of speciali- 
zation in the position of the veins understandable. Compare these three figures 
with those of Anthocharid genera on Plate I, Vol. xxxvii, of these PROCEEDINGS. 
Fig. 23. TZeracolus subfasciatus, Type of genus. An African form more 
generalized than Lurymus (see PROCEEDINGS OF THE AMERICAN PHILOSOPHI- 
CAL SOCIETY, Vol. xxxvii, Pl. II, Fig. 8), with which it must be compared. It 
seems ancestral to Zurymus, in that #2 has retained original position. 
Fig. 24. Amynthia merula. Type of genus. This figure will serve to illus- 
trate the wings of that line of the Eurymini in which the primaries have assumed 
a leaflike shape. Compare Schm. Hild. Taf. II, Fig. 8, for wings of its ally, 
Colias rhamni. 
Fig. 25. Eronia cleodora. Type of genus. <A generalized, radially five- 
branched form of the Euremini, which should be compared with Zyvoessa and 
Nepheronia. The resemblances suggest that these generalized types approach in 
wing structure. The five-branched types are rare in the Pierids, but in the brush- 
footed butterflies this generalized type of the radius is normal and never aban- 
doned. In the primitive Pierid wing the radius was five-branched, and upon this 
character allthe Hesperiades meet, The greatest divergence from this type is 
to be found in specialized Pierids, such as Portia and Piccarda. 
