to understand how there can still be disbelief in regard
to them. If the many and exact observations which have been carefully
collected and critically discussed, for instance by Poulton ("Essays
on Evolution", 1889-1907, Oxford, 1908, passim, e.g. page 269.) were
thoroughly studied, the arguments which are still frequently urged
against mimicry would be found untenable; we can hardly hope to find
more convincing proof of the actuality of the processes of selection
than these cases put into our hands. The preliminary postulates of
the theory of mimicry have been disputed, for instance, that diurnal
butterflies are persecuted and eaten by birds, but observations
specially directed towards this point in India, Africa, America and
Europe have placed it beyond all doubt. If it were necessary I could
myself furnish an account of my own observations on this point.

In the same way it has been established by experiment and observation
in the field that in all the great regions of distribution there
are butterflies which are rejected by birds and lizards, their
chief enemies, on account of their unpleasant smell or taste. These
butterflies are usually gaily and conspicuously coloured and thus--as
Wallace first interpreted it--are furnished with an easily recognisable
sign: a sign of unpalatableness or WARNING COLOURS. If they were not
thus recognisable easily and from a distance, they would frequently be
pecked at by birds, and then rejected because of their unpleasant taste;
but as it is, the insect-eaters recognise them at once as unpalatable
booty and ignore them. Such IMMUNE (The expression does not refer to all
the enemies of this butterfly; against ichneumon-flies, for instance,
their unpleasant smell usually gives no protection.) species, wherever
they occur, are imitated by other palatable species, which thus acquire
a certain degree of protection.

It is true that this explanation of the bright, conspicuous colours
is only a hypothesis, but its foundations,--unpalatableness, and the
liability of other butterflies to be eaten,--are certain, and its
consequences--the existence of mimetic palatable forms--confirm it in
the most convincing manner. Of the many cases now known I select
one, which is especially remarkable, and which has been thoroughly
investigated, Papilio dardanus (merope), a large, beautiful, diurnal
butterfly which ranges from Abyssinia throughout the whole of Africa to
the south coast of Cape Colony.