Contributions to the theory of natural selection. A series of essays ... By Alfred Russel Wallace ...

RESE-M.BLANCES AMONG ANIMALS,,' 8'
to the Heliconidoe, and that it is therefore equally an
advantage to other insects to be mistaken for them.
There is also another extraordinary fact that we are
not yet in a position clearly to comprehend: some
groups of the Heliconid.e themselves mimic other
groups. Species of Heliconia mimic Mechanitis, and
every species of lNapeogenes mimics some other Heliconideous butterfly. This would seem to indicate that
the distasteful secretion is not produced alike by all
members of the family, and that where it is deficient
protective imitation comes into play. It is tlis, perhaps, that has caused such a general resemblance
among the HeliconidT, such a uniformity of type with
great diversity of colouring, since any aberration
causing an insect to cease to look like one of the family
would inevitably lead to its being attacked, wounded,
and exterminated, even although it was not eatable.
In other parts of the world an exactly parallel series
of facts have been observed. The Danaide and the
Acrseidse of the Old World tropics form in fact one
great group with the Heliconidoe. They have the same
general form, structure, and habits: they possess the
same protective odour, and are equally abundant in
individuals, although not so varied in colour, blue and
white spots on a black ground being the most general
pattern. The insects which mimic these are chiefly
Papilios, and Diadema, a genus allied to our peacock.
and tortoiseshell butterflies. In tropical Africa there is
a peculiar group of the genus Danais, characterized
by dark-brown and bluish-white colours, arranged in