and edible family mimic in every
spot and line of colour sundry other butterflies of an utterly unrelated
and fundamentally dissimilar type, but of so disagreeable a taste as
never to be eaten by birds or lizards. The origin of these curious
resemblances I shall endeavour to explain (after Messrs. Bates and
Wallace) a little farther on: for the present it is enough to observe
that the extraordinary resemblances thus produced have often deceived
the very elect, and have caused experienced naturalists for a time to
stick some deceptive specimen of a fly among the wasps and hornets, or
some masquerading cricket into the midst of a cabinet full of saw-flies
or ichneumons.

Let us look briefly at the other instances of protective coloration in
nature generally which lead up to these final bizarre exemplifications
of the masquerading tendency.

Wherever all the world around is remarkably uniform in colour and
appearance, all the animals, birds, and insects alike necessarily
disguise themselves in its prevailing tint to escape observation. It
does not matter in the least whether they are predatory or defenceless,
the hunters or the hunted: if they are to escape destruction or
starvation, as the case may be, they must assume the hue of all the rest
of nature about them. In the arctic snows, for example, all animals,
without exception, must needs be snow-white. The polar bear, if he were
brown or black, would immediately be observed among the unvaried
ice-fields by his expected prey, and could never get a chance of
approaching his quarry unperceived at close quarters. On the other hand,
the arctic hare must equally be dressed in a snow-white coat, or the
arctic fox would too readily discover him and pounce down upon him
off-hand; while, conversely, the fox himself, if red or brown, could
never creep upon the unwary hare without previous detection, which would
defeat his purpose. For this reason, the ptarmigan and the willow grouse
become as white in winter as the vast snow-fields under which they
burrow; the ermine changes his dusky summer coat for the expensive
wintry suit beloved of British Themis; the snow-bunting acquires his
milk-white plumage; and even the weasel assimilates himself more or less
in hue to the unvarying garb of arctic nature. To be out of the fashion
is there quite literally to be out of the world: no half-measures will
suit the stern decree of polar biology; strict compliance with the law
of winter chan