How bugs avoid becoming lunch

One trick is to look like what you're not - a leaf, a thorn, or perhaps an owl

If you you were as small as a pencil eraser and everybody wanted to eat you, how would you protect yourself? Insects have developed an amazing number of ways to avoid being eaten. This shouldn't be surprising, considering how many different types of insects there are. Joseph Culin, an entomologist (a scientist who studies insects) at Clemson University in South Carolina, estimates that there are more than a million species of insects, with new ones being discovered all the time.

Insects are potential dinners for birds, spiders, bats, frogs, bigger insects, and more. To survive, some hide under leaves or sand. Others take the opposite approach. They protect themselves with bright colors. Wasps are red, yellow, and orange. That gets the attention of birds and spiders. But these predators know that wasps can sting. So when they see these brightly colored insects, they let them be.

Monarch butterflies, multicolored grasshoppers, and red-and-black ladybugs are all poisonous or taste bad to things that might be tempted to eat them. The bright colors are a warning.

A few other insects survive by imitating their poisonous relatives. The viceroy butterfly, for example, looks a lot like the monarch. The viceroy is not poisonous, but because it looks so much like a monarch, predators leave it alone.

The longicorn beetle has black-and-orange stripes that make it look like a wasp. But it's really a beetle that can't sting at all. The frangipani sphinx moth has black, red, and yellow coloring similar to that of the deadly coral snake. That keeps a lot of predators away.

Other insects use camouflage, a disguise that hides them. Some katydids not only look like leaves, they act like leaves. They grab a twig and stay still. They even tremble in the wind, the way leaves do.

Bark-colored mantises sit on bark. Walkingsticks sit unmoving around other sticks and twigs, and are hard for predators to spot. Treehoppers line up on branches and look like a row of thorns. Some insects, in their larval (early) stage of development, have coloring that makes them look like bird droppings. Ew!

If being ugly isn't enough to scare predators away, the peanuthead bug has a full assortment of defenses. It can blend in with the bark of a tree to hide. If that doesn't work, it opens its wings, which have two big spots on the back that look like an owl's eyes. This can scare away a smaller bird or startle it so the peanuthead bug can escape.

Brown lacewing larvae are called trash-carriers. They don't throw away their garbage, such as the remains of their prey. Instead, they store trash on their backs until they are completely hidden underneath it. Birds never think to look under all that garbage for dinner. The larvae of some leaf beetles take this one step further. They never leave their droppings on the ground. Instead, they stack them on their backs until they are covered in droppings.

Unlike people, who wear their skeleton on the inside, insects wear their skeleton on the outside, like a shell. It's called an exoskeleton. An exoskeleton is like a suit of armor. On insects like the scarab beetle, the front wings are very hard and serve as an extra coat of armor.

Because these exoskeletons don't grow, when insects get bigger they shed their old shells and form new ones. At least one caterpillar uses this system as a way to look scary. As it molts (sheds) its old skeleton, it saves the part that went on its head - the head capsule. It stacks the empty capsules on its head. Would you eat something so strange?

Another way to discourage predators is by smell. The stink bug really does stink. It can squirt a foul-smelling liquid from large scent glands on the underside of its body. That's enough to make an attacker lose its appetite.

The bombardier beetle shoots a cloud of poison gas that can kill other insects. If you're close enough, you can hear the pop it makes. It's like a tiny cannon going off. Even ladybugs can produce a bad smell to chase off predators. Have you ever picked up a grasshopper and had it spit on you? It's just unpleasant to humans, but it has a very bad smell up close, and can chase away a predator.

Some insects use hair or spines as a defense. A hairy caterpillar doesn't feel very pleasant in the mouth. The lo moth caterpillar is covered with prickly spines, and a South American katydid has so many spines that its scientific name (Panacanthus cuspidatus) means "all thorn." A frog that tries to taste one of these ends up with a sore tongue and a good lesson in what not to eat.

In South America and Mexico, plant-hoppers are a common meal for a bird called the jacamar. But the plant-hoppers can produce long wax streamers. The jacamar may snap at the wax first because it's an easy target. The wax just falls off, and the insect flies to safety.

If you can't fool or discourage a predator, another tactic is to get away quickly. That's why grasshoppers jump so well. If you could jump like a grasshopper, you could clear a football field in a single hop. Dragonflies fly up to 50 feet per second, which helps them escape from birds. (Scientists who want to study dragonflies also have a lot of trouble catching them!)

Moths are a favorite dinner for bats, which find their meals by "echolocation." Bats send out a series of high-pitched squeaks, then listen for the echoes. Some moths, when they detect bat squeaks, fold up their wings, tuck in their feet, and drop from the sky. Because they're so small and light, they aren't hurt when they hit the ground.

But bats aren't willing to drop along with them, so the moths escape. Some woolly bear moths, when they hear bat squeaks, make their own noises. The sounds mix with the echoes of the squeaks and confuse the bat.

It's a bug-eat-bug world for these tiny creatures, but they manage to survive in an impressive number of ways.

*Kidspace, The Christian Science Monitor, One Norway Street, Boston, MA 02115. E-mail: kidspace@csps.com

(c) Copyright 2000. The Christian Science Publishing Society

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