In Müllerian mimicry, some species with warning colouration come to look like each other. English naturalist Henry Walter Bates first noticed that some distasteful butterflies resembled one another, which he wrote about in 1862. However, he did not give a good explanation; that was left to German naturalist Fritz Müller in 1878. Müller's explanation was simple: "Both species benefit from a common pattern". They share the cost of predators learning of their foul taste. Only one learning experience per predator might well be enough to deter it from eating both species. 