Phylogeny of the Pierines. 327 
To the same borderland of Western Asia and Eastern 
Africa may be assigned the place of origin of Nepheronia, 
which has sent a western branch into Africa, and an 
eastern into the Indian peninsula and Malayan islands, 
one species reaching the Australian continent. The 
African branch has given rise to Hronia proper. Attention 
has already been drawn to the curious fact that the form 
which links the Hronia group most closely with Teracolus, 
viz., H. (?) lucasw, survives in Madagascar. Hebomoia, 
another offshoot of this part of the Pierine stock, is now 
almost entirely Malayan ; its place of origin was, however, 
in all probability further west. The birthplace of Huchloe 
is problematical, but the present distribution of the 
charlonia group, which seems to contain the oldest 
members of the genus, would appear to make it probable 
that the Mediterranean sub-region witnessed the rise of 
this, as of so many other more or less direct descendants 
of Synchloe, from which central area it successively over- 
spread the Palearctic and Nearctic continents. The 
isolated geographical position of Hroessa chilensis is very 
remarkable, its affinities being apparently with Hastern 
rather than Western forms. It is probably, as before 
suggested, a solitary survival of a once more widely- 
spread group, among which were to be found the 
immediate ancestors of the present-day Huchloes. 
No other genus in the whole sub-family has so extensive 
a range as Colias, species of which are found in every one 
of the six great Zoological Regions. Here again, I have 
little doubt that the site of original divergence is Asiatic, 
and is most nearly represented in the present condition of 
‘the earth’s surface by the borderland between the 
Palearctic and Oriental Regions on the north-west 
frontier of India. From this centre one or two species 
have ranged into South Africa and the Indian peninsula ; 
but the greater number have turned northwards, and 
after populating the Palearctic and Nearctic continents 
with numerous species, have penetrated to the circum- 
polar lands within the Arctic Circle, have passed down 
the great mountain chains of Central and South America 
to Chili and Patagonia,and have even established outposts 
in Venezuela and the Sandwich Islands.* 
The powers of dispersal possessed by the genus Terias 
* The occurrence of Colias in the last-named locality is, how- 
ever, not entirely free from doubt. 
