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Caterpillar and Butterfly Defense Mechanisms
Caterpillars are soft bodied and slow moving. This makes them easy prey for predators, like birds, wasps, and mammals to mention just a few. Some caterpillars are even eaten by their fellow caterpillars (like Zebra swallowtail larva which are cannibalistic).
In order to protect themselves from predators, caterpillars use different strategies, including:
- Poison Some caterpillars are poisonous to predators. These caterpillars get their toxicity from the plants they eat. Generally, the brightly colored larva are poisonous; their color is a reminder to predators about their toxicity. Some poisonous caterpillars include the Monarch and the Pipevine Swallowtail.
- Camouflage Some caterpillars blend into their surroundings extraordinarily well. Many are a shade of green that matches their host plant. Others look inedible objects, like bird droppings (the young Tiger Swallowtail larva).
- Eyespots Some caterpillars have eyespots that make them look like a bigger, more dangerous animal, like a snake. An eye spot is a circular, eye-like marking found on the body of some caterpillars. These eyespots make the insect look like the face of a much larger animal and may scare away some predators.
- Hiding Some caterpillars encase themselves in a folded leaf or other hiding place.
- Bad smells Some caterpillars can emit very bad smells to ward off predators. They have an osmeterium, an orange, y-shaped gland on their neck which gives off a strong, unpleasant odor when the caterpillar is threatened. This keeps away dangerous wasps and flies that try to lay eggs in the caterpillar; these eggs would eventually kill the caterpillar as they hatch inside its body and eat its tissues. Many swallowtails have an osmeterium, including the Zebra Swallowtail.
Butterflies are fragile and almost defenseless creatures. They rely on a variety of strategies to protect them from hungry predators. Their predators include birds, spiders, reptiles, other insects (e.g., wasps, flies, and mites), and small mammals.
Most butterflies and moth protect themselves from predators by using camouflage. Some butterflies and moths blend into their environment so well that is it almost impossible to spot them when they are resting on a branch. Some butterflies look like dead leaves (like the Indian leaf butterfly), others look like the bark of a tree (e.g., the carpenter moth).
Some butterflies are poisonous. When a predator, like a bird, eats one of these butterflies it becomes sick, vomits violently, and quickly learns not to eat this type of butterfly. The sacrifice of one butterfly will save the lives of many of its kind (and other species that look like it - see the section on mimicry below).
The Goliath Birdwing is a poisonous butterfly from Indonesia. Its bright colors remind any experienced predators (those who ate one in the past and became sick) that it tastes very bad.
Many poisonous species have similar markings (warning patterns). When a predators learns this pattern (after becoming sick from eating one species), many species with similar patterns will be avoided in the future .
Some poisonous butterflies include the Monarch (which eats the milkweed plant to become poisonous), the Small Postman butterfly, and the Pipevine swallowtail.
Mimicry is when two unrelated species have similar markings.
Batesian mimicry is when a non-poisonous species has markings similar to a poisonous species and gains protection from this similarity. Since many predators have become sick from eating the poisonous butterfly, they will avoid any similar looking animals in the future, and the mimic is protected.
Müllerian mimicry is when two poisonous species have similar markings; fewer insects need to be sacrificed in order to teach the predators not to eat these unpalatable animals.
Tropical Queens Monarch butterflies are two poisonous butterflies that have similar markings. Another example is the poisonous Viceroy which mimics the poisonous Monarch butterfly.
Flying is a major defense of butterflies. The speed varies among butterfly species (the poisonous varieties are slower than non-poisonous varieties). The fastest butterflies (some skippers) can fly at about 30 mile per hour or faster. Slow flying butterflies fly about 5 mph.
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