BUTTERILIES CAUGHT IN S. E. TIBET. 533 



and the Tse La down to Dhirang (Oct. 12tli) on a tributary of 

 the Bhoroli river. This tributary was followed to its source 

 and, crossing the Se La, they reached Tawang on October 16th. 

 After exploring the Nyamjang Valley and the upper waters of the 

 Nye and Loro rivers they travelled through Eastern Bhutan and 

 reached Dewangiri in Assam on November 13th. It may be 

 noted that " Chu " means river and " La " pass in Tibetan. 



Captain Bailey had previously taken a considerable interest in 

 butterflies as may be seen from Mr. South's paper on the butterflies 

 caught by him in 1911 in S. E. Tibet and the Mishmi Hills (J. B. 

 N. H. S. XXII. 345 and 598). The country traversed in 1911 

 lies to the east of that dealt with in this paper and his two journeys 

 have succeeded in practically linking up the fairly well-known dis- 

 trict, Chumbi Valley, Gyangtse, with Western China (Szechuan). 

 About 2,000 butterflies were obtained in 1913 belonging to nearly 

 200 species. 



From a natural history point of view, the country traversed may 

 be divided into five well-marked districts : — 



A. — The Lower Tsang Po Valley, known as Pemako, below the 

 gorge where the river breaks through the main range, also the 

 country to the east towards the Mishmi Hills, May 15th to June 

 23rd. A densely wooded district with a heavy rainfall, elevation 

 3,000 to 7,000 feet. Here the greatest number of species were 

 obtained, as might perhaps have been expected. The fauna resem- 

 bled that of Upper Assam, showing a transition more or less to that 

 of Western China. Of the 102 species captured the following may 

 be noted as of especial interest : — 



I^rehia narasingha, M. 



Euhpis narcaea, Hewt. 



Lethe armandii, Oberth. 



Y'ptkima methorina medusa, Leech. 



Galinaga davidis, Oberth. 



Gonepteryx amintha, Blanch. 

 5.— The Po Chu Valley, district Pome, June 23rd to July 13th, 

 well wooded with a moderate rainfall; elevation 7,000, passes up to 

 14,300 feet. This proved an interesting country, as, though the 

 Po Chu is a tributary of the Tsang Po, the two valleys are separated 

 by snowy ranges. As compared with the Lower Tsang Po district, 

 a marked change is noticeable in the fauna and all the 64 species 

 obtained were palaearctic ; of these the following were of interest : — 



Pararge thihetana albicans, South. 



Argynnis paphia and gong. 

 Four Aporias. 



A large form of Lycoena pheretes. 

 Two Pamphilas. 

 Three Erebias. 



