ost as brilliant an azure blue
as the males. A parallel case to this is the occurrence, in the small
islands of Goram, Matabello, Ke, and Aru, of several distinct species of
Euploea and Diadema, having broad bands or patches of white, which do not
exist in any of the allied species from the larger islands. These facts
seem to indicate some local influence in modifying colour, as
unintelligible and almost as remarkable as that which has resulted in the
modifications of form previously described."

After endeavouring to explain some of the facts in a way to be noticed
directly, Mr. Wallace adds:[64] "But even the conjectural explanation now
given fails us in the other cases of local modification. Why the species of
the Western Islands should be smaller than those further east; why those of
Amboyna should exceed in size those of Gilolo and New Guinea; why the {85}
tailed species of India should begin to lose that appendage in the islands,
and retain no trace of it on the borders of the Pacific; and why, in three
separate cases, the females of Amboyna species should be less gaily attired
than the corresponding females of the surrounding islands, are questions
which we cannot at present attempt to answer. That they depend, however, on
some general principle is certain, because analogous facts have been
observed in other parts of the world. Mr. Bates informs me that, in three
distinct groups, Papilios, which, on the Upper Amazon, and in most other
parts of South America, have spotless upper wings, obtain pale or white
spots at Para and on the Lower Amazon, and also that the AEneas group of
Papilios never have tails in the equatorial regions and the Amazon valley,
but gradually acquire tails in many cases as they range towards the
northern or southern tropic. Even in Europe we have somewhat similar facts,
for the species and varieties of butterflies peculiar to the Island of
Sardinia are generally smaller and more deeply coloured than those of the
mainland, and the same has been recently shown to be the case with the
common tortoiseshell butterfly in the Isle of Man; while _Papilio
Hospiton_, peculiar to the former island, has lost the tail, which is a
prominent feature of the closely allied _P. Machaon_.

"Facts of a similar nature to those now brought forward would no doubt be
found to occur in other groups of insects, were local faunas carefully
studied in relation to those of the surrounding countries; and they seem to
in