HEADLEE] + A STUDY IN BUTTERFLY WING-VENATION 293 
We must now make use of the anal area. Inasmuch as the anal 
veins in the front wings of some Rhopalocera, such as Anosia (plate 
figs. 12 and 20), have been reduced more rapidly than those of the 
hind wings, while in other forms, such as Papilio (plate figs. 22 and 
24), the anal veins of the hind wings have been reduced more 
rapidly than those of the front wings, the rhopalocerous progenitor 
must have had the same number of anal veins in each wing. Like- 
wise, inasmuch as the frenate Heterocera exhibit a similar varia- 
tion, the butterfly stem must have separated from the frenate stem 
while the number of anal veins in each wing was the same. 
The Rhopalocera, according to this view, separated from the other 
Frenate while the number of anal veins in each wing was the same 
and when R,,. became split-back to the base of radius. 
In the preceding discussion I have tried to make the following: 
points : 
1. Radius of the rhopalocerous front wing exhibits a split-back 
condition of radius-four-plus-five. 
2. This modification, now almost lost in the adult wings, char- 
acterized the wings of the primitive Rhopalocera, 
3. Radius of the heterocerous front wing exhibits no traces of such 
a modification, and such a modification is therefore not characteristic 
of the primitive frenate Heterocera. 
4. This modification of radius is a phylogenetic difference between 
butterflies and moths and is one of the characters on which the two 
groups diverge. 
5. This divergence took place after the Frenate had separated 
from the Jugatz, while the number of anal veins in the front and 
in the hind wings was the same, and when radius-four-plus-five be- 
. came split-back to the base of radius. 
In conclusion, I wish to acknowledge my indebtedness to Dr. A. D. 
MacGillivray whose helpful suggestions and criticisms have been 
invaluable, and to Prof. J. H. Comstock whose criticism and willing- 
ness to furnish material have made the execution of this work 
possible. 
List oF ABBREVIATIONS 
C—Costal vein or trachea. 
Sc—Subcostal vein or trachea. 
Sc, and Sc.—First and second branches of subcosta. 
R—Radial vein or trachea. 
R,, R., Rz, R, and R,—First, second, third, fourth, and fifth branches of 
radius. 
