d species, belonging to the same two genera, equally close in
their resemblance, may be found. Altogether no less than ten genera are
enumerated, which include species that imitate other butterflies. The
mockers and mocked always inhabit the same region; we never find an
imitator living remote from the form which it imitates. The mockers are
almost invariably rare insects; the mocked in almost every case abounds
in swarms. In the same district in which a species of Leptalis closely
imitates an Ithomia, there are sometimes other Lepidoptera mimicking
the same Ithomia: so that in the same place, species of three genera of
butterflies and even a moth are found all closely resembling a butterfly
belonging to a fourth genus. It deserves especial notice that many of
the mimicking forms of the Leptalis, as well as of the mimicked forms,
can be shown by a graduated series to be merely varieties of the same
species; while others are undoubtedly distinct species. But why, it may
be asked, are certain forms treated as the mimicked and others as the
mimickers? Mr. Bates satisfactorily answers this question by showing
that the form which is imitated keeps the usual dress of the group to
which it belongs, while the counterfeiters have changed their dress and
do not resemble their nearest allies.

We are next led to enquire what reason can be assigned for certain
butterflies and moths so often assuming the dress of another and
quite distinct form; why, to the perplexity of naturalists, has nature
condescended to the tricks of the stage? Mr. Bates has, no doubt, hit on
the true explanation. The mocked forms, which always abound in numbers,
must habitually escape destruction to a large extent, otherwise they
could not exist in such swarms; and a large amount of evidence has now
been collected, showing that they are distasteful to birds and other
insect-devouring animals. The mocking forms, on the other hand, that
inhabit the same district, are comparatively rare, and belong to
rare groups; hence, they must suffer habitually from some danger, for
otherwise, from the number of eggs laid by all butterflies, they would
in three or four generations swarm over the whole country. Now if a
member of one of these persecuted and rare groups were to assume a dress
so like that of a well-protected species that it continually deceived
the practised eyes of an entomologist, it would often deceive predaceous
birds and insects, and thus often escape des