200 THE ENTOMOLOGIST. 



list of these interesting Himalo-Chinese species : — Byasa ravana, 

 B.plutojiius, B. alcinous, B. latreillii, Panosmiopsis janaka, Addl- 

 lides krisJma, A. arcturiis, A. polyctor, Cadugoides agestor, C. go- 

 vindra, Patliysa paphus, Dabasa gyas, Teniopalpus imperialis, and 

 Armandia lidderdalii. 



Some of these also occur at equivalent elevations upon 

 the plateau of the Cossyas in Assam, where in fact the exceed- 

 ingly magnificent T. imperialis seems to have its metropolis, 

 judging from its more frequent occurrence there than in the 

 Himalayas. Darjeeling (where I made my headquarters) at the 

 altitude of 7500 ft. above the level of the sea is situated towards 

 the upper limits of the warm temperate zone, the mean annual 

 temperature being 65° Fahrenheit. Here, as elsewhere on the 

 sub-Himalayas or Outer Hills, particularly those which are in 

 close proximity to the deep hot tropical valleys, such as the 

 Teesta and the Eungeet, several otherwise strictly tropical species 

 occasionally ascend to the highest limits of this zone, a complete 

 list of them, according to my own observations, being as follows : 

 — Ornitlioptera cerherus, Pangerana astorioii, Panosmiopsis rhe- 

 tenor, Achillides paris, Sarbaria ganesa, Iliades agenor, Sainia 

 protenor, Chants helenus, C. chaoTiy Dalchina sarpedon, Zetides 

 agamemnon. Three others — Byasa dasarada, B. pkiloxenus, and 

 Dalchina cloanthus — are almost equally characteristic of the 

 tropical and temperate zones, the two former occurring regularly 

 up to 8000 ft., the latter up to 7000 ft., at least in the North- 

 west Himalayas. 



On the outer hills, from 7500 ft. up to fully 10,000 ft. above 

 the sea-level, the peculiar Himalo-Chinese element (of which I 

 have given a list), although in decreasing numbers, continues to 

 predominate, that is to the extreme confines of the cold-temperate 

 zone, with its deciduous trees of Central European aspect and 

 appearance, but this is in reality rather owing to a paucity of 

 palffiarctic species of Ehopalocera than to a plentifulness of Indo- 

 Chinese forms, and the same phenomenon precisely holds good 

 with respect to nearly all the other groups of insects also. In 

 the "interior" of Sikkim, however — that is, on the southern 

 declivities of the meridional ridge of the great central snow 

 peaks — the preceding condition of things begins to become 

 reversed as low as 8000 ft., where, owing to a much drier 

 atmosphere and a sunnier though colder climate, the temperate 

 fauna and flora commence to predominate at a lower altitude 

 than upon the outer hills, where the precipitation is so excessive, 

 but the only representative of the palsearctic Papilionidae which 

 exists therein is a local form of the common Papilio machaon, 

 which, however, is exceedingly plentiful in certain places. Even 

 here there are several "Papilios" of Indo-tropical character, but 

 they are all very scarce apparently in individuals. On the 

 outer " hills " within the present zone the following may be 



