316 Dr. Frederick A. Dixey on the 
which it usually retains in the former. It is not very 
easy to form an opinion as to the relative antiquity of 
the four Western genera; if we are to judge from the 
pupe, so far as they are known, it would seem that 
Aphrissa has undergone less modification than either 
Phebis or Callidryas. Another possible indication of 
the greater antiquity of Aphrissa is afforded by the 
shape and size of the palpi, which in this genus, 
especially in the females, show less departure than is the 
case in either Phebis, Metura, or Callidryas, from the 
Colias and Gonepteryx type. -Phebis with its offshoot 
Metura, from which it differs only in the contour of the 
wings, is probably the most highly specialised genus of 
all; this being shown by the possession of a tuft of 
long hairs on the hindwing of the male, which is not 
found in Aphrissa and Callidryas, and by the absence in 
most species of nearly all indication of dark ground- 
colour from the upper surface. It is remarkable that 
the Western genera just treated of are less closely akin 
to the South American Amynthia than is the Hastern 
genus Catopsilia, and especially the African C. florella. 
The genus Hronia seems to represent a branch of the 
present section which leaves the main stem somewhere 
between the points marked by Teracolus and Imias. 
With the exception of the presence of a fifth subcostal 
in the forewing (which, however, is sometimes wanting), 
the neuration of Hronia agrees fairiy with that of 
Teracolus. The antennee in Hronia differ in different 
species, but are all intermediate between the Teracolus 
and the Colias type; and the pupa of H.cleodora, with 
its very convex and prominent keel, is ike that of one 
of the stout forms of Teracolus, e.g., T. evarne. The 
assemblage of species distinguished by Mr. Butler as 
Nepheronia is probably older than Hronia proper, as is 
shown by the tendency of its antennz to terminate in a 
definite club, like the more ancient genus Teracolus. 
N. thalassina also retains a primitive Pierie feature in 
the yellow precostal streak of the hindwing underside, 
which again is found in some species of Teracolus. 
Eronia proper, on the other hand, is slightly nearer to 
Teracolus in neuration. The curious Hronia (?) lucas 
from Madagascar, which has only four subcostal nervules 
in the forewing, and whose antenne are slender, with a 
definite club, is probably one of the oldest and most 
