Lepidoptera of Sikkim. 273 
middle or temperate zone from 5000 up to about 10 or 
12,000 ft., which, though mostly of subtropical character, 
is largely peopled by birds, plants, and insects peculiar 
to the mountainous region extending from Kashmir to 
Sumatra and Formosa, which I then christened the 
Himalo-Chinese subregion. Thirdly, the alpine zone, 
above 12,000 ft., which belongs to and is inhabited by 
forms peculiar to or characteristic of the Palearctic 
region.* 
But, though the distribution of Lepidoptera is very 
similar to that of birds, yet many of the genera as at 
present recognised are much more cosmopolitan in their 
range, and 1 do not find that the middle zone contains 
anything like the same proportion of peculiar species 
or genera of Lepidoptera in proportion to the lower one, 
as it does in the case of birds and plants. I also notice 
that the upper zone, especially in the outer hills, where 
the rainfall is much heavier than in the interior, is 
much poorer both in abundance and variety of species 
than might be expected from its great extent and eleva- 
tion, and from the great number and variety of species 
which are found in the adjoining regions of Turkestan 
and China. This, however, may be accounted for by 
the extreme moisture of the climate, and the prevalence 
of rain and mist during the summer or rainy season, 
which lasts almost without intermission from May till 
October. It is also probable that a better knowledge of 
the drier valleys and mountains of the interior at an 
elevation of 9—14,000 ft. will add many new species. to 
the few which we at present have obtained through our 
native collectors, as it must be remembered that no 
European has hitherto collected insects systematically at 
a higher elevation than 12,000 ft. in the Kastern Hima- 
layas, and that the interior valleys are as yet practically 
untouched. 
It seems to be unquestionable that a damp and sun- 
less climate, even if warm, is much less favourable to 
the abundance of Diurnal Lepidoptera, both as regards 
individuals and species, than a dry sunny one, even if 
the summers are short and the winters severe; and 
therefore we find a far greater abundance of species and 
individuals of butterflies in the lowest valleys of Sikkim, 
* The mean temperature of Darjeeling, 7500 ft. elevation, is 
about 55° Fahy. ; monthly average, highest 64°, lowest 41°. 
