28 GROTE—THE DESCENT OF THE PIERIDS. (Jan. 5, 
Mx, which ascends the radius to a little less than one-third 
of the distance between cross-vein and external margin. Cell 
closed, the vein a little degenerate, concave, J/2 being thrown 
off from upper corner and apparently fuses with radius. A trace 
of fork to second anal. Hind wings with humeral spur straight, 
apparently turning outwardly at tip; subcostal vein solid at base ; 
discal cell closed, cross-vein somewhat reduced. 
A highly specialized form, as seen by the three-branched radius, 
the ascent by J4/1 of the radius and the position of J/2 on the 
primary wing. The following represents a more generalized stage : 
Gen. Phrissura Butler, 1871. 
Type: Pacezis. 
Phrissura egis. : 
Wings entire; radius four-branched; 2 has not left the cell, 
but is advanced nearly to cross-vein; #3 a short furcation out of 
R4+5. Cell closed; A/r ascends radius; Jd/2 radial, out of 
cross-vein which is concave between radius and A/2. Trace of 
fork at base of second anal. Hind wing with humeral vein 
pointed, turning sharply toward apices. 
This type very nearly assumes the stage of Pzer¢s and stands much 
lower than //lodina. It is a little more specialized than Pvevzs, 
since #2 is nearer cross-vein, not quite assuming the position of 
Trifurcula. 
Gen. Ascia Scopoli, 1777. 
Type: A. monuste. 
Ascia monuste. 
This genus assumes almost completely, apparently by conver- 
gence, the Prerzs stage. The four-branched radius shows the rela- 
tive position of Ar and A2 asin Preris. It is very slightly more 
generalized than Pverzs, in that J72 is further from radius, not con- 
tinuous with the short cross-vein between J/2 and radius. Hind 
wings with humeral spur pointed, turning sharply, as in PArts- 
sura, toward apices, not abbreviate as in Prerzs. 
Gen. AM/ylothris Hiibner, 1816. 
Type: M. rhodope. 
Mylothris rhodope. 
Wings ample, entire; radius four-branched ; &1 and #2 in 
the Pieris position; fork of #3 with A4-+ 5 longer than in 
