466 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XI. 



appears to have been hitherto overlooked, and which I take to be the 

 Ladak form of C. nastes, Boisduval. This very widely distributed species 

 occurs in some form or other in many parts of the world, either at great 

 elevations or in an arctic climate. I have it from Labrador ; in quantities 

 from the mountains of Lapland, where it appears to hybridize with 

 C. hecla, Lefebvre; from the Rocky Mountains of Alberta, where it occurs 

 above timber-line in the Bow River valley ; from near Fort Churchill in 

 Hudson's Bay under the name of C. moina, Strecker ; and from the 

 Pamir of Central Asia at 1 6,000 feet under the name of C. cohandica, 

 Erschoff. C. nebulosa, Oberthiir, from Ta-tsien-lo, also seems to belong 

 to the nastes group. The males of this new form, which I propose to 

 call C. nastes, var. leechii, are more lemon-coloured than in either form 

 of C. nastes above-mentioned, and at first sight might be taken by a 

 casual observer for C. ladahensis Felder, which also occurs in Ladak, 

 but the females, which are much like those of C. cohandica, Erschoff, are 

 of a very pale yellowish-white, whereas the females of C. ladahensis are of 

 a brighter yellow than the males. They may easily be distinguished from 

 C. sieversi, Groum Grshimailo, and C. sifanica, Groum Grshimailo, 

 by the smaller size and conspicuous markings of the hindwing and 

 underside, and from C. montium, Oberthiir, which they very closely 

 resemble, in the colour of the upperside in both sexes and by the dark 

 basal area of the hindwing below. 



Thus it seems that we have in the British Trans-Himalayan region 

 the following species of Colias, namely :— 



C. eogene, Felder, 



C. stoliczhanus^ Moore, 



C. ladahensis, Felder, and 



C. nastes, var. leechii, Elwes. 

 Mr. McArthur, to whom I wrote on the subject of a possible inter- 

 breeding between C. eogene and C. stoliczhanus, writes as follows : — 

 Both Colias eogene and C. stoliczhanus I found very local on the 

 mountain-side leading to the Khardong Pass. They overlapped each 

 other in this way ; I was busy with C. stoliczhanus and would now and 

 again capture one C. eogene. Higher up the mountain, say 800 feet, 

 C. eogene was common and C. stoliczhanus rare, the intermediate 

 ground producing a few of each species, the headquarters of each being 

 quite distinct ; I never found one species in copula with the other." 



