, and frequent the borders of streams and the
edges of puddles, where they gather together in swarms consisting of
several species, greedily sucking up the moisture, and, when disturbed,
circling round in the air, or flying high and with great strength and
rapidity.

_Geographical Distribution._--One hundred and thirty species of Malayan
Papilionidae are now known within the district extending from the Malay
peninsula, on the north-west, to Woodlark Island, near New Guinea, on
the south-east.

The exceeding richness of the Malayan region in these fine insects is
seen by comparing the number of species found in the different tropical
regions of the earth. From all Africa only 33 species of Papilio are
known; but as several are still undescribed in collections, we may raise
their number to about 40. In all tropical Asia there are at present
described only 65 species, and I have seen in collections but two or
three which have not yet been named. In South America, south of Panama,
there are 150 species, or about one-seventh more than are yet known from
the Malayan region; but the area of the two countries is very different;
for while South America (even excluding Patagonia) contains 5,000,000
square miles, a line encircling the whole of the Malayan islands would
only include an area of 2,700,000 square miles, of which the land-area
would be about 1,000,000 square miles. This superior richness is partly
real and partly apparent. The breaking up of a district into small
isolated portions, as in an archipelago, seems highly favourable to the
segregation and perpetuation of local peculiarities in certain groups;
so that a species which on a continent might have a wide range, and
whose local forms, if any, would be so connected together that it would
be impossible to separate them, may become by isolation reduced to a
number of such clearly defined and constant forms that we are obliged to
count them as species. From this point of view, therefore, the greater
proportionate number of Malayan species may be considered as apparent
only. Its true superiority is shown, on the other hand, by the
possession of three genera and twenty groups of Papilionidae against a
single genus and eight groups in South America, and also by the much
greater average size of the Malayan species. In most other families,
however, the reverse is the case, the South American Nymphalidae,
Satyridae, and Erycinidae far surpassing those of the East in number,