302 Dr. Frederick A. Dixey on the 
by the importation of any new feature as by the 
brightening up and extension of features already present, 
and indeed often common to the whole subfamily. The 
reason for this ornamentation is doubtless the same in 
both cases—namely, to call attention to inedible qualities. 
The Hastern genus, however, seems to have itself become 
a model for mimicry (Wallace in Trans. Ent. Soc. Lond., 
3rd series, iv., pp. 309, 344), while the Western genera 
have modified their ancestral form in order to join an 
alien company of inedible insects. 
The genus Prioneris, though differing slightly from 
Delias in neuration and other structural characters, is 
probably nearly akin to it, and represents, so far as the 
colouring is concerned, a similar degree of antiquity in 
the Pierine stock. ~The close resemblance of pattern 
between different species of Delias and Prioneris, to 
which reference has already been made (pp. 258, 284, 
etc.), is no doubt a true case of mimicry, but represents 
probably the result rather of arrested divergence than 
of the acquisition by Prioneris of new imitative features. 
The two groups that have just been discussed, namely, 
those formed by Delias and Prioneris in the Old World, 
and by Catasticta, Leodonta, Huterpe, and Pereute in the 
New, thus constitute together a second grade, as it were, 
in Pierine development. The only earlier species yet 
mentioned is Hucheira socialis, but there exist certain 
other forms which appear to be but little inferior to that 
insect in antiquity ; and to these, with Hucheira, the 
name of “ Pierines of the first grade” may be applied. 
One of the forms now referred to is Metaporia agathon. 
This remarkable insect is probably the representative of 
an ancient group of Pierines, among which were to be 
found the common ancestors of the two second-grade 
assemblages already mentioned, and which, no doubt, 
supplied the link at present wanting between Hucheira 
and Catasticta. The relation of Metaporia with the Hastern 
assemblage is more direct than with the Western, for 
although it offers points of structural difference from 
Delias, it shows, nevertheless, a condition of the primi- 
tive Pierine pattern which is in all essentials identical 
with that of the earlier kinds of that genus. The cor- 
respondence of its markings on the upper surface with 
those of Delias belladonna and D. eucharis is at once 
evident, and, like D. belladonna, it has a patch of bright 
