BUTTERFLIES. 167 



be seasonally dimorphic, the dry-season form being C. gnoma, 

 Fabricius, the wet-season form being C. chryseis, Drury. Both forms 

 are found ia Sikhim with true C. pyranthe, which ajjpears to be an 

 intermediate form. 



423. Teeias hecabe, Linnajus. 



Common in Sikhim as elsewhere, and flies all the year round at 

 low elevations. Mr. Elwes records it from Tonglo, 10,000 feet, but 

 it is only stragglers that extend their flights to so great an elevation. 



424. Terias kana, Moore. 

 A common species in Sikhim. 



425. Teeias silhetana, Wallace. 



Lieutenant E. Y. Watson has recently shown that this species may 

 be known by having three dark streaks or spots in the discoidal cell 

 of the forewing on the underside in addition to the reniform spot 

 defining the disco-cellular nervules, while T. hecabe never has more 

 than two streaks or spots in • addition to the reniform one. It also 

 is a common species in Sikhim. 



426. Terias l^eta, Boisduval. 



Rare in Sikhim, recorded from 7,000 to 9,000 feet from July 

 to September. 



427. Terias eama, Moore. 



Also rare ; occurs from 2,000 to 9,000 feet. This is probably the 

 species which is recorded by Elwes as T. vcnata^ Moore. 



428. Teeias libythea, Fabricius. 



Found at the foot of the hills only and is rare almost throughout 

 the year. It is recorded by Elwes under its synonymic name of 

 T. rubella, Wallace. 



429. Terias haeina, Horsfield. 



Occurs at low elevations only and is never common. Flies from 

 April to December. 



430. Colias fieldii, Mdn6tri6s. 



Rare in Darjeeling itself, far more common in the interior at 

 high elevations. It is found from 5,000 to 12,000 feet, and flies 

 throughout the warm months according to the elevation. At the 

 lowest elevation it is found almost throughout the cold weather. 

 Occurs also in Western and Central China. 



431. Dercas verhuellii, van der Hoeven. 



Local, but where it occurs abundant. Found at about 4,000 feet 

 from May to October. 



432. Deecas WALLicnii, Doubleday. 



Mr. Elwes records a single specimen from the interior. It is a 

 common species in the Khasi Hills and in Western and Central China. 



