Phylogeny of the Pierinee. 325 
species of Mylothris belong possibly to the same 
category. 
The genera derived from the Catasticta group remain, 
for the most part, within the confines of the Neotropical 
Region. This is the case with Pieris, Leptophobia, 
Hesperocharis, the American species of Mylothris,* Dis- 
morphia, Moschoneura, and those species allied to 
monuste at present included in the genus Udaiana.t 
It is remarkable that the Nearctic Region does not 
furnish a single species that can be supposed to be 
derived from the present stem.{ Inasmuch, however, 
as the Palearctic genus Leptosia seems to belong 
rather to this than to any Eastern branch, the conjecture 
may be hazarded that connecting forms now extinct 
once occupied the Nearctic Region, from which the 
Palearctic continent received the forerunners of its 
present Leptosias, probably by way of Behring Strait. 
Turning now to the Eastern Metaporia, which inhabits 
the borderland between the Palearctic and Oriental 
Regions, we find it emitting one clearly-defined branch 
in the Palearctic direction. This is the branch to 
which belong the various species of Pontia, as P. nabel- 
lica, P. soracta, P. hippia, P. belucha, P. leucodice, and 
P. crategi. In the Chilian or Andesian division of the 
Neotropical Region we find the genus Tatochila, which 
appears not to belong to the regular Neotropical Pierine 
stock, but to be closely related to the Palearctic 
Pontias. It is conceivable that the latter stem may 
have spread from Asia into the western portion of the 
Nearctic continent, and thence down the mountain- 
chains to the south. Neophasia menapia, at present 
inhabiting the Californian and Rocky Mountain sub- 
regions, seems to me to be more nearly allied to both 
Pontia and Tatochila than (as Behr thinks) to Huchetra 
socialis, and may very possibly be a relic of the original 
invasion, Another indication of the same invasion is 
afforded by the genus Phulia, now found with the 
nearly-allied Tatochila only in the Andesian or Chilian 
* See p. 320, note. 
+ See p. 321. 
+ The instance of U. monuste, which straggles into the southern 
districts of the Nearctic Region, hardly forms an exception to the 
above statement. 
