Phylogeny of the Pierinee. 283 
special feature does not often occur in a very clearly- 
marked condition; it is, however, present in Xanthidia 
nicippe, and in several species of Terias and Sphcnogona, 
as 7’. agave and WS. mexicana; it may also be seen 
occasionally in Teracolus, as in T’. antevippe, T. ewpompe, 
and (sometimes) 1’. erts, assuming in this genus a some- 
what diffuse appearance. In some species of Appias, as 
A. hombroni (occasionally), and A. lyncida, as also in 
Herpexnia eriphia, there are deep yellow marks near the 
root of the wing, which are probably homologous with 
part of the patch now under discussion; and in the 
genera Belenois and Tatochila touches of deep yellow 
often occur at the base of the median space, though not 
in the cell, which appear to correspond with the marks 
just referred to in Appias and Herpxnia (see B. mesentina 
and J’. autodice). ‘These yellow touches in Belenois are 
undoubtedly members of the series spoken of on p. 279, 
and so far it would seem that the well-marked pink patch 
at the root of the cell in Colias, Gonepteryzx, etc., is at 
least in part developed from a portion of that series, of 
which another member has given rise to the yellow 
precostal streak. It is certain, however, that other 
factors besides the series now indicated are chiefly, 
though probably not entirely, answerable for the com- 
position of the pink basal patch in Colias; and it is at 
least possible, as will presently be seen, that the pre- 
costal streak itself owes something to their assistance. 
These other factors are the red basal areas to which 
reference has already been made, and which will now be 
examined in greater detail. 
c. The red basal areas. ‘To begin with the under- 
side of Delias pasithoe, we find the base of the hind- 
wings occupied by a bright red patch forming about 
a quarter of a circle on each wing, the body itself and the 
immediately surrounding area of the wings being black. 
The spaces affected by the red patch are six ; namely, the 
precostal, costal, subcostal (or cell), median, submedian, 
and internal—all those in fact whose apices reach to the 
base of the wing. In D. thisbe there occurs a similar 
red patch, occupying nearly the same spaces. In this 
insect, however, there is no red in the precostal space, 
which is occupied (as above noticed, p. 280) by the ordinary 
yellow precostal streak ; while the red patch, which in this 
butterfly is visible on the upper as well as the underside 
