lities,
which latter were believed to be wholly free from the attacks of
insectivorous birds. Then came the extension of the principle, by Dr. F.
Mueller, to the case of species of distinct genera of the inedible
butterflies resembling each other quite as closely as in the former
cases, and like them always found in the same localities. They derive
mutual benefit from becoming, in appearance, one species, from which a
certain toll is taken annually to teach the young insectivorous birds
that they are uneatable. Even when the two or more species are
approximately equal in numbers, they each derive a considerable benefit
from thus combining their forces; but when one of the species is scarce
or verging on extinction, the benefit becomes exceedingly great, being,
in fact, exactly apportioned to the need of the species.

The third extension of the same principle explains the grouping of
allied species of the same genera of inedible butterflies into sets,
each having a distinct type of coloration, and each consisting of a
number of species which can hardly be distinguished on the wing. This
must be useful exactly in the same way as in the last case, since it
divides the inevitable toll to insectivorous birds and other animals
among a number of species. It also explains the fact of the great
similarity of many species of inedible insects in the same locality--a
similarity which does not obtain to anything like the same extent among
the edible species. The explanation of the various phenomena of
resemblance and mimicry, presented by the distasteful butterflies, may
now be considered tolerably complete.

_Mimicry in other Orders of Insects._

A very brief sketch of these phenomena will be given, chiefly to show
that the same principle prevails throughout nature, and that, wherever a
rather extensive group is protected, either by distastefulness or
offensive weapons, there are usually some species of edible and
inoffensive groups that gain protection by imitating them. It has been
already stated that the Telephoridae, Lampyridae, and other families of
soft-winged beetles, are distasteful; and as they abound in all parts of
the world, and especially in the tropics, it is not surprising that
insects of many other groups should imitate them. This is especially the
case with the longicorn beetles, which are much persecuted by
insectivorous birds; and everywhere in tropical regions some of these
are to be found so completely dis