are in little
danger during the day. It is in the evening, or on moonlight nights,
when they go to drink, that they are chiefly exposed to attack; and Mr.
Francis Galton, who has studied these animals in their native haunts,
assures me, that in twilight they are not at all conspicuous, the
stripes of white and black so merging together into a gray tint that it
is very difficult to see them at a little distance. We have here an
admirable illustration of how a glaringly conspicuous style of marking
for recognition may be so arranged as to become also protective at the
time when protection is most needed; and we may also learn how
impossible it is for us to decide on the inutility of any kind of
coloration without a careful study of the habits of the species in its
native country.]

[Footnote 86: The principle of colouring for recognition was, I believe,
first stated in my article on "The Colours of Animals and Plants" in
Macmillan's _Magazine_, and more fully in my volume on _Tropical
Nature_. Subsequently Mrs. Barber gave a few examples under the head of
"Indicative or Banner Colours," but she applied it to the distinctive
colours of the males of birds, which I explain on another principle,
though this may assist.]

[Footnote 87: Quoted by Darwin in _Descent of Man_, p. 317.]

[Footnote 88: In the _American Naturalist_ of March 1888, Mr. J.E. Todd
has an article on "Directive Coloration in Animals," in which he
recognises many of the cases here referred to, and suggests a few
others, though I think he includes many forms of coloration--as
"paleness of belly and inner side of legs"--which do not belong to this
class.]

[Footnote 89: For numerous examples of this protective colouring of
marine animals see Moseley's _Voyage of the Challenger_, and Dr. E.S.
Morse in _Proc. of Bost. Soc. of Nat. Hist._, vol. xiv. 1871.]

[Footnote 90: See _Origin of Species_, p. 107.]

[Footnote 91: The "Geographical Variation of North American Squirrels,"
_Proc. Bost. Soc. of Nat. Hist._, 1874, p. 284; and _Mammals and Winter
Birds of Florida_, pp. 233-241.]

CHAPTER IX

WARNING COLORATION AND MIMICRY

The skunk as an example of warning coloration--Warning colours
among insects--Butterflies--Caterpillars--Mimicry--How mimicry
has been produced--Heliconidae--Perfection of the
imitation--Other cases of mimicry among Lepidoptera--Mimicry
among protected groups--Its explanation--Extension of the
prin