In Batesian mimicry in insects, an edible insect looks similar to an aposematic, inedible insect. The inedible insect is called the model, and the lookalike species is called the mimic. Hungry predators that have tried to eat the unpalatable model species learn to associate its colors and markings with an unpleasant dining experience. The predator will generally avoid wasting time and energy catching such a noxious meal again. Because the mimic resembles the model, it benefits from the predator's bad experience.
Batesian mimicry was so named for the 19th century naturalist Henry Bates, who first described this defensive strategy. Bates observed and collected butterflies in the Amazon region, and incorporated Charles Darwin's theory of natural selection into his work on mimicry in insects.
Successful Batesian mimicry communities depend on an imbalance of unpalatable versus edible species. The mimics must be limited in number, while the models tend to be common and abundant. For such a defensive strategy to work for the mimic, there must be a high probability that the predator in the equation will first attempt to eat the inedible model species. Having learned to avoid such foul-tasting meals, the predator will leave both the models and mimics alone. When tasty mimics become abundant, predators take longer to develop an association between the bright colors and the indigestible meal.
Numerous examples of Batesian mimicry in insects are known. Many insects mimic bees, including certain flies, beetles, and even moths. Few predators will take the chance of getting stung by a bee, and most will avoid eating anything that looks like a bee.
Birds avoid the unpalatable monarch butterfly, which accumulates toxic steroids called cardenolides in its body from feeding on milkweed plants as a caterpillar. The viceroy butterfly bears similar colors as the monarch, so birds steer clear of viceroys, too. While monarchs and viceroys have long been used as a classic example of Batesian mimicry, some entomologists now argue this is really a case of Müllerian mimicry.