200 THE ENTOMOLOGIST. 
list of these interesting Himalo-Chinese species :—Byasa ravana, 
B. plutonius, B. alcinous, B. latreillii, Panosmiopsis janaka, Achil- 
lides krishna, A. arcturus, A. polyctor, Cadugoides agestor, C. go- 
vindra, Pathysa paphus, Dabasa gyas, Teniopalpus imperialis, and 
Armandia lidderdalit. 
Some of these also occur at equivalent elevations upon 
the plateau of the Cossyas in Assam, where in fact the exceed- 
ingly magnificent 7’. 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 55° 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 Rungeet, 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 : 
—Ornithoptera cerberus, Pangerana astorion, Panosmiopsis rhe- 
tenor, Achillides paris, Sarbaria ganesa, Iliades agenor, Sainia 
protenor, Charus helenus, C. chaon, Dalchina sarpedon, Zetides 
agamemnon. Three others—Byasa dasarada, B. philoxenus, 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 1 
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 
palearctic species of Rhopalocera 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 Jower altitude 
than upon the outer hills, where the precipitation is so excessive, 
but the only representative of the palearctic Papilionide which 
exists therein is a local form of the common Papilio machaon, 
which, however, is exceedingly plentiful in certain places. Hven 
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 
