The Malay Archipelago, Volume 1 _ The Land - Alfred Russel Wallace

Insects furnish us with similar facts wherever sufficient data are to be had, but
owing to the abundant collections that have been made in Java, an unfair
preponderance may be given to that island. This does not, however, seem to be
the case with the true Papilionidae or swallow-tailed butterflies, whose large size
and gorgeous colouring has led to their being collected more frequently than
other insects. Twenty-seven species are known from Java, twenty-nine from
Borneo, and only twenty-one from Sumatra. Four are entirely confined to Java,
while only two are peculiar to Borneo and one to Sumatra. The isolation of Java
will, however, be best shown by grouping the islands in pairs, and indicating the
number of species common to each pair. Thus:—