Protective coloration

(I am now afflicted by two separate medical conditions — neither of them life-threatening, but the two of them together absorbing most of my day — so this is a Mary, Queen of Scots Not Dead Yet posting. Real content, but a brief job of composition for me. I have not forgotten Zippy and his dots.)

Passed on to me by Jens Fiederer this morning, a Gary Larson Far Side cartoon I don’t recall having seen before:

(#1) Protective coloration saves lives

From Wikipedia’s article on animal coloration, in a section on Edward Bagnall Poulton’s classification of the forms of protective coloration:

Protective resemblance is used by prey to avoid predation. It includes special protective resemblance, now called mimesis, where the whole animal looks like some other object, for example when a caterpillar resembles a twig or a bird dropping. In general protective resemblance, now called crypsis, the animal’s texture blends with the background, for example when a moth’s colour and pattern blend in with tree bark. [AZ: see the Larson cartoon]

Aggressive resemblance is used by predators or parasites. In special aggressive resemblance, the animal looks like something else, luring the prey or host to approach, for example when a flower mantis resembles a particular kind of flower, such as an orchid. In general aggressive resemblance, the predator or parasite blends in with the background, for example when a leopard is hard to see in long grass.

For adventitious protection, an animal uses materials such as twigs, sand, or pieces of shell to conceal its outline, for example when a caddis fly larva builds a decorated case, or when a decorator crab decorates its back with seaweed, sponges and stones.

In variable protective resemblance, an animal such as a chameleon, flatfish, squid or octopus changes its skin pattern and colour using special chromatophore cells to resemble whatever background it is currently resting on (as well as for signalling).

The main mechanisms to create the resemblances described by Poulton … are crypsis, blending into the background so as to become hard to see (this covers both special and general resemblance); disruptive patterning, using colour and pattern to break up the animal’s outline, which relates mainly to general resemblance; mimesis, resembling other objects of no special interest to the observer, which relates to special resemblance; countershading, using graded colour to create the illusion of flatness, which relates mainly to general resemblance; and counterillumination, producing light to match the background, notably in some species of squid.

Two famous cases from the literature, cited by Larson in his caption:

the peppered moth. Extended piece on this case on the BBC site, in “Famous peppered moth’s dark secret revealed” by Jonathan Webb on 6/1/16. In the sooty conditions of the Industrial Revolution, the normal checkered variant of the moth was replaced in cities by a black variant (and has now returned to cities as air pollution has been mitigated):

(#2) Checkered variant on the right, black variant on the left

the Arctic hare. From J. Giannetta’s (Regina, Saskatchewan) Sakschools site on Canadian animals / Arctic animals, in June 2000:

(#3) The Arctic hare in summer

(#4) The Arctic hare in winter

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