a form of biological resemblance in which two or more unrelated noxious, or dangerous, organisms exhibit closely similar warning systems, such as the same pattern of bright colours. According to the widely accepted theory advanced in 1878 by the German naturalist Fritz Müller, this resemblance, although differing from the better-known Batesian mimicry (in which one organism is not noxious), should be considered mimicry nonetheless, because a predator that has learned to avoid an organism with a given warning system will avoid all similar organisms, thus making the resemblance a protective mechanism.