Phylogeny of the Pierinee. 3138 
The genus Xanthidia is transitional between Colias 
and Terias, in neuration coming nearer the latter. ‘The 
pattern on the upper side is scarcely modified from that of 
Colias; on the under surface, however, 8 has lost much 
of the distinctness it possesses in so many species of the 
latter genus, and its relics take part in a general 
mottling which is very probably protective in object. 
In Terias the resolution of series Sand M, which is still 
visible in most of the females and many of the males of 
Colias, has usually disappeared from the upper surface ; 
the underside of the hindwings, however, generally shows 
S in a somewhat modified condition. The pink edging 
to the wings, so characteristic of Colias, and occasionally 
visible in Xanthidia nicippe, is indicated in several 
species of Terias, as T’. messalina, T. delia, and 1’. rhodia, 
The pupa of Terias is more sharply acuminate and re- 
curved than that of Colias (see pupa of 7. mandarina and 
T. eecavata in Coll. B. Mus.). 
Sphenogona presents in pattern no marked differences 
from Yerias, with which genus it is so closely allied. 
S. gratiosa, like T. agave, X. nicippe, and some other 
species of these genera, shows a relic of the pinkish Colias- 
patch at the root of the cell on the underside of the 
hindwing. In neuration, Sphenogona, while generally 
resembling Terias, is peculiar in emitting the first and 
second subcostal branches of the hindwing from a short 
footstalk beyond the end of the cell. In this respect it is 
intermediate between Verias and Leucidea, which latter 
genus presents no markings to guide us, but has no 
doubt taken its origin directly or indirectly from Terias.* 
Another probable descendant of Terias is the genus 
Nathalis, which agrees very fairly with Terias in neuration, 
except that it wants one nervule in the forewing, probably 
a branch of the subcostal. There isa striking resemblance 
of pattern between N. iola and TJ. elathea 3. In the 
absence of paronychia Nathalis reverts to the condition of 
Colias. 
Pyrisitia seems to represent an early offshoot of the 
stem leading from Colias to Terias. In most points it 
* Staudinger and Schatz (op. cit., Theil. ii, p. 66, etc.) consider 
Leucidea to be more closely related to Pontia (Nychitona) than to 
Eurema (Terias). The balance of evidence seems to me to be 
against this view. 
TRANS. ENT. 800, LOND. 1894,—PaRT II. (JUNE.) X 
