322 Dr. Frederick A. Dixey on the 
2. The evidence of distribution. 
It now remains to briefly indicate the bearing of the 
geographical distribution of the various forms that have 
been mentioned upon the question of their kinship and 
relative antiquity. 
As we have already seen, the oldest form of Pierine 
now extant is probably Hucheira socialis. This insect 
appears to be as limited in its geographical range as it is 
isolated in its zoological position, for itis found only in the 
mountain-ranges of Mexico, which may be considered as 
a southern extension of the “ Rocky Mountain” division 
of the Nearctic Region.* Its nearest allies appear to be 
Behr’s two species of Neophasia (see p. 303), which inhabit 
the same region with itself, and the Pontias and Metaporias 
of the high lands of Central Asia, most of which forms 
are known to retain the ancient larval habit of spinning. 
These facts seem to point to the conclusion that Hucheira 
is the relic of an archaic group of Pierines which once 
occupied the great mountain regions of both the Palw- 
arctic and Nearctic continents, and whose immediate 
descendants, still represented in the Hast by Metaporia 
and Pontia, have in the West become extinct (unless 
Behr’s Neophasia be a survival) after giving origin to 
the group of genera headed by Catasticta. 
From one or other of these two primary stems, the 
Kastern or the Western, nearly the whole of the existing 
genera of Pierines may be derived. There are, however, 
a few exceptions, which, perhaps, constitute relics of an 
ancient Pierine fauna coeval with the groups above 
mentioned, but not, like them, the progenitors of a 
numerous and varied offspring. The chiet of these are 
the genera Hlodina and Nychitona, the former of which 
is entirely confined to the Australian Region, while the 
latter has a very wide distribution throughout the 
Hthiopian, Oriental, and Australian. The African 
* T here follow Mr. Sclater’s division of the earth’s surface into 
six Zoological Regions, which arrangement, adopted by Mr. Wallace 
in his “‘ Geographical Distribution of Animals,” 1876, has stood the 
test of time and experience better, in my opinion, than any alterna- 
tive distribution that has been proposed. I also adopt, for conve- 
nience, the smaller divisions, or “sub-regions,” as determined by 
Mr. Wallace in the above-named work. 
