4 
INTRODUCTION. By Dr. A. Seitz. 
The Larentiinae become decidedly less numerous in the tropics. They inhabit principally light forests 
with tall tree-trunks, and such forests are almost unknown to tropical Nature with its luxuriant growth. In 
the Palaearctic Region we have named no less than 1500 forms; the whole of British India numbers only 
204 species. Ceylon, according to Hampson (1893), harbours scarcely 50 species, while e. g. Griebel in his 
Fauna of the Rheinpfalz cites even for this limited area three times that number. Southwards the Larentiinae 
again increase in number rapidly. In the southern part of Australia especially they are of everyday occurrence 
and on New Zealand they attain the ascendancy, not only over the Geometrids in particular but even over the 
whole of the Lepidoptera occurring there. 
In aspect the Indo-Australian Larentiinae present nothing extraordinary; most are of moderate or 
even small size; forms like the East Asiatic Gandaritis, Triphosa, etc. are scarcely reached, let alone surpassed. 
Peculiar to the region are the numerous green Sauris ; almost all very rare, extremely slender moths, found both 
in India and in Australia and having lobes on the inner margin of the male hindwing leading over to the 
Lobophora group. Here we come upon the highly remarkable species of the Tatosoma group, with the ab¬ 
domen elongate almost as in a dragon-fly; they are found in New Zealand, but South America also possessed 
some quite near relatives of equally fantastic appearance. Eu.pithecia produces throughout quite similar forms 
in the Indo-Australian Region to the European; in their life-history, time of flight, frequency, etc., the last- 
named group also shows in the Indian fauna the constancy attaching to it throughout the rest of the world. 
By far the greatest number of Indo-Australian Geometric! species falls to the subfamily Boar- 
miniae, and here belong too the largest known geometers. Such are the giant forms of the genus Meda- 
sina, already mentioned above; also Erebomorpha, which may reach an expanse of 8 or 9 cm., Elphos, 
Xandrames and Amblychia, the latter expanding 11—12 cm. Thence there are all transitions in size to 
some tiny Boarmia and very small Macaria. Similarly we find here every conceivable colour, although grey, 
yellow and brown are the commonest. Here again we have a genus which — like Celerena in the Oenochrominae 
and D ysphania in the Hemitheinae -—- stands entirely outside the typical scheme; namely Milionia, which ex¬ 
tends from China and N. India to Australia and especially is widely-distributed over the intervening islands. 
In this genus bright carmine-red or orange bands are placed on a deep-black ground, often adorned with a 
metallic gloss and there is sometimes an astonishing degree of variability in individuals of the same species. 
Beside these marvellously beautiful developments, to which the Geometrids of the Palaearctic North afford 
no analogy, we find also forms very familiar to us northerners, such as certain Abraxas, representatives of our 
Boarmia crepuscularia and selenaria, etc., reaching far towards Australia. Altogether this subfamily shows 
such diversity as scarcely to admit of many generalisations and we refer the reader to the special part of this 
volume for further details. 
In their general habits the Geometrids of the Indo-Australian Region do not differ essentially from 
then’ palaearctic relatives. There is nothing parallel to that which we noticed regarding the Noctuids, namely 
that their resting habits by day differ in the tropics from those of our northern species. We mentioned concer¬ 
ning this, that in the tropics it is quite rare to find Noctuids asleep on tree-trunks, palings or walls, the usual 
resting-places of the family in the temperate zone. In addition to the explanation that the brilliance of the 
tropical sunshine and the great abundance of their enemies which patrol the trees may be uncongenial to the 
Noctuids, there is yet this further fact, that most of the tropical Noctuidae belong to genera other than those 
( Mamestra , Hadena, Acronicta, Catocala, etc.) which characterize our fauna. The few outliers of the more tro¬ 
pical Noctuid groups which reach the Palaearctic Region, such as the Heliothinae (Heliothis ), Acontiinae 
( Taarche, Acontia), Calpinae ( Calpe ), Ophiusinae ( Ophiusa .), Ommatophorinae ( Patula .), Hypopyrinae ( Spirama ), 
Euclidiinae (Euclidia ), etc., do not even in the more temperate North rest on tree-trunks and walls. From this 
we can understand that for the Geometridae a different law holds, inasmuch as Boarmia, Cidaria, Acidalia , 
Eupithecia, etc., are of constant occurrence in the Indo-Australian Region under much the same conditions as 
with us, and therefore, being nearly related to the representatives of our fauna, behave in the same manner. 
They have the habit of sitting with wings spread out flat on rocks, fences, tree-trunks, etc., just as with us. As 
for the few geometrid genera of the Indo-Australian fauna which are entirely unrepresented with us, such as 
Eumelea, Dysphania, Celerena, etc., their hiding-places when at rest seem hard to discover; they appear to be 
chiefly day-fliers and to conceal themselves by night among foliage, for it only rarely happens that a specimen 
of even one of the quite common species is disturbed out of the bushes. 
Economically the Geometrids of the Indo-Australian Region are apparently of little importance. In 
plantations in India we find the Cinnamon Geometer ( Fascellina chromataria) on cinnamon bushes and several 
Boarmiine larvae on tea. The latter, however, like our Boarmias, do not seem to do any damage worth men¬ 
tioning, or at any rate the tea plantations of Ceylon suffer much less from the depredations of Geometrids than 
from certain Chalcosiinae larvae. 
