a kind of mimicry between closely allied species as well as between
species of distinct genera, all tending to the same beneficial end. This
may be seen in the four or five distinct species of the genus Heliconius
which all have the same peculiar type of coloration--a yellow band
across the upper wings and radiating red stripes on the lower,--and are
all found in the same forests of the Lower Amazon; in the numerous very
similar species of Ithomia with transparent wings, found in every
locality of the same region; and in the very numerous species of Papilio
of the "Aeneas" group, all having a similar style of marking, the
resemblance being especially close in the females. The very uniform type
of colouring of the blue-black Euplaeas and of the fulvous Acraeas is of
the same character.[107] In all these cases the similarity of the allied
species is so great, that, when they are on the wing at some distance
off, it is difficult to distinguish one species from another. But this
close external resemblance is not always a sign of very near affinity;
for minute examination detects differences in the form and scalloping of
the wings, in the markings on the body, and in those on the under
surface of the wings, which do not usually characterise the closest
allies. It is to be further noted, that the presence of groups of very
similar species of the same genus, in one locality, is not at all a
common phenomenon among unprotected groups. Usually the species of a
genus found in one locality are each well marked and belong to somewhat
distinct types, while the closely allied forms--those that require
minute examination to discriminate them as distinct species--are most
generally found in separate areas, and are what are termed
representative forms.

The extension we have now given to the theory of mimicry is important,
since it enables us to explain a much wider range of colour phenomena
than those which were first imputed to mimicry. It is in the richest
butterfly region in the world--the Amazon valley--that we find the most
abundant evidence of the three distinct sets of facts, all depending on
the same general principle. The form of mimicry first elucidated by Mr.
Bates is characterised by the presence in each locality of certain
butterflies, or other insects, themselves edible and belonging to edible
groups, which derived protection from having acquired a deceptive
resemblance to some of the inedible butterflies in the same loca