334 W. HOVANITZ 



tropics at lower elevations and the cooler regions higher in the 

 mountains. 



Nathalis resembles Kricogonia in having a limited distributional 

 range from 5° to 35° N. Lat. ; within this range, however, it occupies 

 a wide altitudinal belt up to 4,000 meters (but typically only to 

 3,000 meters). It has failed to pass from the North American tropics 

 into the South American tropics despite the apparent absence of a 

 barrier. 



The Euchloinae comprise six genera the distribution of which, for 

 such a small group, is especially diverse: two are wholly northern, 

 three are wholly southern, and one is equatorial with a southern 

 expansion. Euchloe, a typical northern type, is found as far north as 

 60° N. Lat. with a sea level extension along the Pacific Coast to 

 30° N. This pattern is nearly duplicated by that of Anthocharis , 

 with the exception that the latter extends farther south, to 25° N. 

 Lat. at elevations of 3,000-4,000 meters, and thence to 15° at 2,000 

 to 3,000 meters. 



Eroessa duplicates, to a certain extent, these distributions south 

 of the equator, covering elevations of from 1,000 to 3,000 meters 

 with a latitudinal range from 25° to 40° S. Lat. Hesperocharis is the 

 connecting link between the genera of the southern hemisphere and 

 those of the northern hemisphere. It covers all elevations from sea 

 level to 3,000 meters, from 20° N. Lat. to 20° S. Lat., and, in addi- 

 tion, extends southward up to 1,000 meters to 45° S. Lat. It thus 

 overlaps in distributional range all other genera except Eiichloe. 



Andina is represented by a very limited distributional range at 

 4,000-5,000 meters elevation in the Andes, from 15° to 20° S. Lat. 

 Phalia extends this range downward to 2,000 meters, over a lati- 

 tudinal range from 15° to 25° S. Lat. These distributions appear to 

 indicate that the Euchloinae are a closely knit group with specific 

 temperature tolerances, with the possibility that the basic origin of 

 the group was tropical and that its northern {Euchloe, Anthocharis) 

 and southern (Eroessa, Andina, Phalia) representatives were inde- 

 pendently derived from the tropical Hesperocharis, or from its 

 ancestors. Of course it is always possible that the entire American 

 group was derived from Asiatic representatives, via Euchloe and 

 Anthocharis, that Hesperocharis was derived from these, and the 

 southern types from Hesperocharis. The direction of derivation 

 cannot be deduced from present day distributions alone. 



