104 
Psyche 
[December 
THE PERSIUS GROUP OF THANAOS 
(LEPIDOPTERA, HESPERIIDAE) 
By William T. M. Forbes, 
Cornell University, Ithaca, New York 
This group has been a standing problem for many years. 
On the one hand, the superficial and genitalic differences of 
the adults are so small that the late Dr. Skinner and various 
other workers were convinced that there was only a single 
variable species. On the other hand, the earliest rearings 
showed that there were two widely divergent foodplants 
(columbine and willow or poplar), associated with visible 
differences in appearance of the butterflies ; and later work 
has added Baptisia as a third, — each belonging to a different 
and widely separated family of plants. This for the East ; 
in Arizona we must add afranius Lintner, and California 
has a complex that only local rearing can straighten out. 
In this paper I am taking the persius group in its strictest 
sense, comprising only the forms with genitalia of identical 
plan: socii rather long, equal in size and spike-like (one 
more curved than the other) ; left valve with three strong 
lobes, the middle one longitudinal in general direction, right 
valve two-lobed, with a short tooth on the upper outer angle 
of the lower lobe, to represent the middle lobe of the left 
side. This definition will include the three eastern types, 
afranius, and California specimens identical in structure 
with persius and afranius, but will exclude the Californian 
lUitts and callidus, also pernigra if rightly identified at the 
National Museum. T. avinoffi of Alaska probably is also 
included, but has not been examined structurally. 
I use the name Thanaos for familiarity. Erynnis may 
be defended on the basis of the code, but has no effective 
use in this sense, and substantial use in another subfamily ; 
so should be excluded by a conservanda ruling if the code 
continues to function. 
The present paper is drawn up from the eastern point of 
