Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

190 THE MAIAYAN PAPILIONIDA AS
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 PapilionidTa 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 Nymphalidme,
Satyridea, and Erycinidam far surpassing those of the
East in number, variety, and beauty.
The following list, exhibiting the range and distribution of each group, will enable us to study more
easily their internal and external relations.
Range of the Groups of AfIalayan Papilionidce.
Ornithoptera.
1. Priamus-group. Moluccas to Woodlark
Island................. 5 species.
2. Pomrpeus- group. Himalayas to New
Guinea, (Celebes, maximum)...... 11,,
3. Brookeana-group. Sumatra and Borneo... 1,,