icuous by adjacent black markings,
probably assists the individuals in keeping together; and appearances
with probably the same interpretation are found in many birds. The white
upturned tail of the rabbit is probably of use in enabling the
individuals to follow each other readily. The difference between a
typical aposematic character appealing to enemies, and episematic
intended for other individuals of the same species, is well seen when we
compare such examples as (1) the huge banner-like white tail,
conspicuously contrasted with the black or black and white body, by
which the slow-moving skunk warns enemies of its power of emitting an
intolerably offensive odour; (2) the small upturned white tail of the
rabbit, only seen when it is likely to be of use and when the owner is
moving, and, if pursued, very rapidly moving, towards safety.

_Mimicry_ (see also MIMICRY) or _Pseudo-sematic Colours_.--The fact that
animals with distant affinities may more or less closely resemble each
other was observed long before the existing explanation was possible.
Its recognition is implied in a number of insect names with the
termination -_formis_, usually given to species of various orders which
more or less closely resemble the stinging Hymenoptera. The usefulness
of the resemblance was suggested in Kirby and Spence's _Introduction to
Entomology_, London, 1817, ii. 223. H. W. Bates (_Trans. Linn. Soc._
vol. xxiii., 1862, p. 495) first proposed an explanation of mimicry
based on the theory of natural selection. He supposed that every step in
the formation and gradual improvement of the likeness occurred in
consequence of its usefulness in the struggle for life. The subject is
of additional interest, inasmuch as it was one of the first attempts to
apply the theory of natural selection to a large class of phenomena up
to that time well known but unexplained. Numerous examples of mimicry
among tropical American butterflies were discussed by Bates in his
paper; and in 1866 A. R. Wallace extended the hypothesis to the
butterflies of the tropical East (_Trans. Linn. Soc._ vol. xxv., 1866,
p. 19); Roland Trimen (_Trans. Linn. Soc._ vol. xxvi., 1870, p. 497) to
those of Africa in 1870. The term mimicry is used in various senses. It
is often extended, as indeed it was by Bates, to include all the
superficial resemblances between animals and any part of their
environment. Wallace, however, separated the cryptic resemblances
already described,