ZOO-GEOGRAPHICAL DIVISIONS* 
23 
at all, being holarctic, and we take the dividing line to be at about 6,000 
feet. The extreme North-West of India is also not strictly “ Indian 55 
but is holarctic. Burmah, we exclude, as being Malayan and Indo- 
Chinese, and the hills of Assam are strictly Indo-Chinese in part. “ In¬ 
dia ?? proper then does not include these areas at all and it must be clear¬ 
ly borne in mind that in these pages we do not use India in the sense 
that the “ Fauna of India 55 does : the term “ British India ” is used 
throughout this volume for the political India covered by the Fauna ; 
the term “ India ?? includes tropical and subtropical India, i.e. t up to 
about 6,000 feet; “ subtropical India ” denotes the moist forested 
slopes of the hills usually between 2,000 and 6,000 feet; “ tropical 
India ” or “ the plains ” means the great stretches of India lying 
between sea-level and about 2,000 feet, usually not forested and 
extending from Tinnevelly in the South to Bawai Pindi in the North, 
from the border of Sind and Baluchistan in the West to the Assam and 
Surma valleys in the East. It is the insects of this area that are 
discussed in these pages and for one insect in this area there are at least 
five in “ subtropical India. ” 
The frontispiece illustrates the divisions of tropical India according 
to fauna so far as we are able to tentatively delimit them; the faunal zones 
of subtropical India are not indicated. In considering this question fully, 
the factors to be considered are (1) the physical features of the country ; 
(2) the geological formation composing it; (3) its climate ; and (4) its 
flora. The first three probably affect insects in much the same way as 
they affect plants, and we may take the flora as the basis of our 
divisions; Sir J. D. Hooker, in his sketch of the flora of British India, 
divides the whole area into nine provinces as follows 
(1) Eastern Himalayas.— Sikkim to Mishmi mountains in Upper 
Assam. 
(2) Western Himalayas — -Kumaun to Chitral. 
(3) Indus Plain.— Punjab, Sind, Kajputana, west of the Araval- 
li range and the Jumna river, Cutch and Gujarat (to the 
Tapti). 
(4) Gangetie Plain.— From the Aravalli Hills and the Jumna 
river to Bengal, the Sundarbans, the plains of Assam, 
the low country of Orissa north of the Mahanadi. 
