6 Watson, Calinaga, Single Genus of a Sub-family. 



regions of both the Palearctic and Nearctic continents, 

 and whose immediate descendants, still represented in the 

 East 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 " ; and 

 again {Loc. cit., p. 323) he says : " Turning now to the 

 Eastern Metaporias 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. Nabellica, Hippia, Soracta, Belucha, Lencodice, 

 and CratcBgi." In these remarks we thus have evidence 

 that the high lands of Central Asia (the home of the 

 peculiar monotypic genera before-mentioned) form a 

 locality in which we might reasonably expect to find 

 some ancient types of lepidopterous fauna. That it 

 is in highly-elevated regions generally or in regions 

 which, though their altitude is much lower, nevertheless 

 agree with them in an isothermal sense and in the 

 length of their summer, that these ancestral forms of 

 butterflies are most likely to be found, there is very 

 abundant proof in Weissman's Studies in the Theory of 

 Descent, " On the seasonal dimorphism of butterflies," 

 where he states, in discussing the parent form of our 

 common Pieris Napiiy^x. Bryon(2),^ very dark-veined form 

 which is found in the higher alps of Europe, in Lapland at 

 low elevations, and in Alaska at sea-level. " In both regions 

 (meaning polar regions and higher alps) Bryonce produces 

 but one generation in the year, and thus, according to my 

 theory, must be regarded as the parent form oi Pieris 

 Aapi." His subsequent temperature experiments amply 

 confirmed his theory. In Thibet we also get some very 

 dark forms of Pierids, closely allied to Bryoncs, one of 

 which, in Oberthlir's opinion has enough claim to be 



