Most insects are quite vulnerable to predation. If you can't overpower your enemy, you can try to outsmart him, and that's just what Batesian mimics do to stay alive.
What Is Batesian Mimicry?
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.
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.
Examples of Batesian Mimicry
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.
Henry Bates and His Theory on Mimicry
Henry Bates first proposed this theory on mimicry in 1861, building on Charles Darwin's views on evolution. Bates, a naturalist, collected butterflies in the Amazon and observed their behavior. As he organized his collection of tropical butterflies, he noticed a pattern.
Bates observed that the slowest flying butterflies tended to be those with bright colors, but most predators seemed uninterested in such easy prey. When he grouped his butterfly collection according to their colors and markings, he found most specimens with similar coloration were common, related species. But Bates also identified some rare species from distant families that shared the same color patterns. Why would a rare butterfly share the physical traits of these more common, but unrelated, species?
Bates hypothesized that the slow, colorful butterflies must be unpalatable to predators; otherwise, they'd all be eaten rather quickly! He suspected the rare butterflies gained protection from predators by resembling their more common but foul-tasting cousins. A predator that made the mistake of sampling a noxious butterfly would learn to avoid similar-looking individuals in the future.
Using Darwin's theory of natural selection as a reference, Bates recognized evolution was at play in these mimicry communities. The predator selectively chose prey which least resembled the unpalatable species. Over time, the more precise mimics survived, while the less exact mimics were consumed.
The form of mimicry described by Henry Bates now bears his name - Batesian mimicry. Another form of mimicry, in which entire communities of species resemble one another, is called Mullerian mimicry after German naturalist Fritz Müller.