1900. } GROTE—THE DESCENT OF THE PIERIDS. 3) 
Pierids may be best compared with that of the Limnadidz among 
the brush-footed butterflies, but is most clearly more specialized. 
The cells are closed, but the transverse vein is often degenerate. 
There are still, sometimes, very small backward spurs, slight 
remainders of the vanished base of the median system. The 
cubital cross-vein has left no mark. The fork to the second anal 
vein of the fore wings at base is very thin and transparent. The 
trace of the first anal vein has usually disappeared. The upper me- 
dian branches ascend the radius, in the specializing movement 
attending the disintegration of the system of the media. The 
radial branches are reduced at times to three, the usual number is 
four, and very rarely the five original branchlets are retained on the 
primary wing. On the hind wings the humeral cell is reduced, often 
the central slit can with difficulty be discerned, and sometimes the 
veins appear to be here completely fused and the subcostal to be 
single. The humeral spur is usually present, but vanishes in spe- 
cialization. ‘There are two anal veins on the secondaries. These 
characters show that the Pierids belong to the second division of 
the diurnals, in which the free and short downwardly curved third 
anal vein of the fore wings of the Papilonides is absent, viz., the 
Hesperiades. 
_An antecedent specialization has taken place on the hind wings 
in that the radius is single, or, if we adopt the view that it is fur- 
cate at base and that the costal cell is formed by Rr, two 
branched. Present specialization seems still to favor the seconda- 
ries, as in those Nymphalids in which the cell is open on hind wings 
and closed on primaries, the reverse‘appears never to happen. But 
in the Parnassiidz and the Pierids the progressing disintegration 
of the median system appears more marked now on the primaries, 
where the upper branches ascend the radius and the cross-vein 
weakens. 
PHYLOGENY. 
Not without much trouble have I been able to detach the ter- 
minal branch of the Hesperiades from what clings, and yet seems 
not to belong to it, on the lepidopterous tree. From a common 
pattern with separated veins, the middle branch of the disinte- 
grating median system fading out at length (2% sztz) in both Blues 
and Skippers, owing to the shrinkage of the connecting cross-vein, 
the wings of the Lyczenids have evidently emerged, losing the gen- 
