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