1900. } GROTE—THE DESCENT OCF THE PIERIDS. 19 
tions, indicating the vanished base to the median system. The 
two upper branches of the median system ascending the lower side 
of the radius in specialization. (The second branch follows suit in 
Phulia as well as in Pseudopontia.) M2 radial. The fork to the 
second anal vein of primaries is usually, perhaps always, present, 
rigid, very thin and transparent. Hind wings with the subcostal 
cell lost, the subcostal vein solid at base ; in some species, ¢. ¢., 
Hebomoia glaucippe, there is a narrow slit perceivable. I have 
therefore assumed that all traces of A1 have generally disappeared 
and lettered the Subcosta S. alone ; the fact that the radius is theo- 
retically furcate at base has no practical value here. The humeral 
spur (precostal spur) is usually present ; in some specialized forms, 
e. g., Nathalis, Colias, it has vanished ; in some subspecialized gen- 
era, Eurema, Zerene, Phedis, it has left a slight projection. Discal 
cell of secondaries closed. M2 radial. Two anal veins. As 
compared with the Lyczeni-Hesperiadz branch, the neuration shows 
more complex changes, the relations more netlike. 
No characters of the wings, or, in fact, other, have been found by 
me by which a subdivision of the Pierididz could be effected. Where 
there are no gaps there are no categories. The generastand in various 
degrees of relationship toward each other; there is a tendency to form 
lines, culminating in a form with three radial branches, terminat- 
ing in one with the generalized number five. I have indicated 
these lines in a former communication to the American Philoso- 
phical Society. The phylogenetic lines come out more clearly in 
the holarctic fauna; as we approach the tropics the increased num- 
ber of forms render their separation quite difficult. Ihave no doubt 
I have often failed to give the true relationship; at least, I have 
tried to do this, to express by a lower position the fact that the 
form so placed displays here a neurational feature which a succeed- 
ing form has abandoned ; this is in principle what is intended by 
phylogeny. 
A rough division into ‘‘ Whites’ and ‘*‘ Yellows ’’ from the pre- 
vailing colors of the wings has been attempted. Since these groups 
cannot be actually limited, they merit no Latin term. As often as 
I have tried to express their characteristics I have desisted, fearing 
to dwell upon exclusive marks. In Prerzs and Colas, or Hurymus, 
we have a typical expression of the two associations, which are pos- 
sibly really natural groups kept apart by general color. 
Since the most specialized form I have found belongs to the im- 
