The resemblance of one animal to another, which has evolved as a means of protection or improving predation efficiency. In Batesian mimicry, named after British naturalist Henry Bates (1825–92), the markings of certain harmless insects closely resemble the warning coloration of another insect (the model). Predators that have learnt to avoid the model will also avoid good mimics of it. This phenomenon is often found among butterflies. Müllerian mimicry, named after German zoologist J. F. T. Müller (1821–97), involves the mutual resemblance of a group of animals, all harmful, such as the wasp, bee, and hornet, so that a predator, having experienced one, will subsequently avoid them all. In aggressive mimicry, a predator or parasite gains some advantage in adopting a resemblance to another species. A notable master of marine disguise is the mimic octopus (Thaumoctopus mimicus), discovered in 1998, which can change shape and appearance for either defence or attack. Among its many guises it can imitate a crab in order to approach real crabs so they can be caught more easily. To avoid being predated itself it can mimic a sea snake by extending two tentacles and burying the remainder in the seafloor. See also molecular mimicry.

http://www.ucl.ac.uk/~ucbhdjm/courses/b242/Mimic/Mimic.html Summary of the lecture ‘Warning colour and mimicry’, from the Department of Biology, University College London