eover, Papilio dardanus is by
no means the only species of butterfly which exhibits different kinds of
colour-pattern on its wings. Many species of the Asiatic genus Elymnias
have on the upper surface a very good imitation of an immune Euploeine
(Danainae), often with a steel-blue ground-colour, while the under
surface is well concealed when the butterfly is at rest,--thus there are
two kinds of protective coloration each with a different meaning! The
same thing may be observed in many non-mimetic butterflies, for
instance in all our species of Vanessa, in which the under side shows
a grey-brown or brownish-black protective coloration, but we do not yet
know with certainty what may be the biological significance of the gaily
coloured upper surface.

In general it may be said that mimetic butterflies are comparatively
rare species, but there are exceptions, for instance Limenitis archippus
in North America, of which the immune model (Danaida plexippus) also
occurs in enormous numbers.

In another mimicry-category the imitators are often more numerous than
the models, namely in the case of the imitation of DANGEROUS INSECTS by
harmless species. Bees and wasps are dreaded for their sting, and they
are copied by harmless flies of the genera Eristalis and Syrphus, and
these mimics often occur in swarms about flowering plants without damage
to themselves or to their models; they are feared and are therefore left
unmolested.

In regard also to the FAITHFULNESS OF THE COPY the facts are quite in
harmony with the theory, according to which the resemblance must have
arisen and increased BY DEGREES. We can recognise this in many
cases, for even now the mimetic species show very VARYING DEGREES OF
RESEMBLANCE to their immune model. If we compare, for instance, the
many different imitators of Danaida chrysippus we find that, with their
brownish-yellow ground-colour, and the position and size, and more or
less sharp limitation of their clear marginal spots, they have reached
very different degrees of nearness to their model. Or compare the female
of Elymnias undularis with its model Danaida genutia; there is a general
resemblance, but the marking of the Danaida is very roughly imitated in
Elymnias.

Another fact that bears out the theory of mimicry is, that even when the
resemblance in colour-pattern is very great, the WING-VENATION, which is
so constant, and so important in determining the systematic position
of butterflies, is