328 Dr. Frederick A. Dixey on the 
are almost as remarkable as those of Colias ; perhaps 
even more so when we take into account their weak 
flight, and the fact that their migrations must have been 
intertropical Mr. Wallace, however, has drawn 
attention to their habit of frequenting “gardens and 
plantations and skirts of forests rather than their deeper 
recesses,” and also of ‘assembling on the margins of 
streams and on the sea beach,” and has remarked that 
“these habits lead to their being frequently carried olf 
by winds,” and that ‘‘it is thus perhaps that some of the 
species have so wide a range and offer such perplexing 
variations.”* Whatever may have been their means of 
dispersal, there can, I think, be no doubt that they took 
their rise from the Colias stock in the Western Hemi- 
sphere, the line of descent passing through Xanthidia 
to Terias and Sphenogona; Pyrisitia, Nathalis, and 
Leucidea being given off by the way. All these genera 
are mainly Neotropical with Nearctic extensions. Terias 
itself, however, as is well known, so far from remaining 
within these limits, has overspread the warmer portions 
of the Ethiopian, Oriental, and Australian Regions, and is 
even found in the Manchurian sub-region of the Pale- 
arctic. 
It seems on the whole most probable that the origin of 
Gonepteryx is also to be referred to the Western Hemi- 
sphere, where Meganostoma marks the transition from 
Colias. Gonepterya itself seems to have passed to the 
north by way of California and so across into the 
Palearctic Region, while Rhodocera and Amynthia re- 
present a Neotropical development of the same stock, the 
Central American genus Kricogonia perhaps remaining 
near the original seat of divergence. Gonepteryx having 
reached the Palearctic Region has extended to its 
westernmost extremity. Its only offshoot appears to be 
Dercas, which probably arose in the debateable Man- 
churian area, where the Palearctic and Oriental faunas 
are much mixed, and thence spread southwards through 
the Indo-Chinese sub-region to Sumatra and Borneo, 
Catopsilia and Callidryas, like Terias, must, it would 
seem, have undergone intertropical migration. Their 
oldest forms appear to be Catopsilia florella, C. hyblza, 
* Trans. Ent. Soc. Lond., 3rd series, iv., p. 320. See also 
above, p. 325. 
