Beetles: A Comprehensive Guide to These Remarkable Insects

Beetle

Introduction to Beetle

Beetle, an insect with specialized forewings, or outer wings, that form an extremely durable covering called an elytra. There are more species of beetle—more than 300,000 in all—than of any other kind of insect. More than 30,000 species live in North America.

Rhinoceros beetles reach two inches in length.

Many beetles are incorrectly called bugs. The wings of beetles are different from those of bugs. The forewings of most bugs have gauzy tips that overlap at the back. The forewings of most beetles are heavy and horny throughout, meeting in a straight line along the back.

In most species, the beetle's forewings encase and protect the hindwings, or inner wings, which are thin and membranous. To fly, the beetle raises its forewings and unfolds the hindwings. The beating wings typically make a whirring or humming sound. Some species of beetles are poor fliers or do not fly at all. Such beetles are usually swift runners. They may lack hindwings or have ones that are quite small. The forewings of some ground beetles are fused together along the midline of the back.

True bugs have sucking beaks, while most beetles have strong mouths adapted to biting. (The word beetle is derived from the Anglo-Saxon bitan, "to bite.") Depending on the species, the jaws are used for grasping and killing prey, or for gnawing, boring, or chewing The jaws of certain species are large and resemble pincers.

Beetles have three pairs of legs. Some beetles have long, slender legs adapted for running. Others have legs suited for swimming or digging.

Beetles vary greatly in size. Some species are less than 1/16 of an inch (1 mm) long, others grow five to six inches (13 to 15 cm) long. The goliath beetle, a scarab native to Africa, is the heaviest insect known; it can weigh more than two pounds (900 g).

The Habits of Beetles

Beetles live in all parts of the world except in saltwater and the polar regions. Most varieties live on land; many are found in freshwater; and some are at home in either element. Beetles eat many kinds of animal and vegetable matter.

The Colorado potato beetle eats leaves and can destroy crops.

Many beetles are destructive. Some feed on stored skins, furs, and woolens. The larvae of the carpet beetle damage rugs and carpets. May beetles and Japanese beetles devour the leaves of trees and crops. Some species bore into trees and deposit eggs. Other destructive beetles include the Mexican bean beetle, the sugarcane beetle, and various weevils.

Some beetles, such as the ladybugs, or ladybirds, are beneficial, since they destroy insects harmful to plants.

Where in the World Do Beetles Live?

Beetles can be found in deserts, rain forests, grasslands, and freezing cold places. Beetles live on mountains, in lakes and streams, on plains, and in meadows. Beetles have adapted their bodies and their behavior to different climates and conditions. Beetles are great survivors. They were on the earth long before people were.

How Do Some Beetles Play Tricks?

Some beetles camouflage (KAM uh flahzh), or cover themselves up, so that predators cannot see them. Cryptic (KRIHP tihk) beetles have bodies that blend into tree bark, leaves, and other parts of their environment. The darkling beetle you see here is one kind of cryptic beetle.

Most jewel beetles have bright, shiny colors. For some, these colors help attract their prey. Other jewel beetles have colors that fool their predators. For example, some have spots of bright color on their elytra that look like eyes. When they display their elytra, the “eyes” look right at the predator and startle it. This gives the beetle time to fly away to safety.

When Is a Beetle Not Like a Beetle?

When it is trying to look like another insect, that’s when! This is called mimicry (MIM ihk ree). Mimicry is another weapon beetles use to keep predators away. They look and behave like other insects, such as ants, that predators know can fight back. Other beetles mimic flies and butterflies that are fast moving and hard to catch.

The wasp beetle has a long, tapered body that is yellow and black like a wasp’s. Another type of beetle looks like a bumblebee and will try to “sting” any animal that captures it. That should be enough to scare off even the bravest predator.

Life Cycle

In its life cycle, a beetle goes through four stages—it begins as an egg, then becomes a larva, then a pupa, and, finally, an adult. This growth pattern is called a complete metamorphosis.

The female beetle lays her eggs where food is plentiful. After hatching, the larvae (grubs) resemble worms. As a larva grows, it sheds (or molts) its outer skin a number of times. The larvae of some species have protective coverings. When the larva of a tortoise beetle molts, its shed skin becomes attached to small prongs that hold the skin (and feces that the larva deposits on the skin) over the body like a shield.

The full-grown larva becomes a pupa, which does not eat or move about. The pupa slowly changes into an adult beetle, which then begins its search for food and a mate.

Some species of beetles produce several generations each year. Others require five years to complete their metamorphosis.

Kinds of Beetles

Beetles make up the order Coleoptera. The most important families commonly found in the United States and Canada include the following:

Ambrosia Beetles and Bark Beetles (family Scolytidae). Small, cylindrical bodies. Bark beetles burrow into cambium (the layer of cells just under the bark of trees and shrubs), where they lay their eggs and feed on cambium and bark. Ambrosia beetles burrow into heartwood, where they lay their eggs and feed on a type of fungus that grows there. The tunnels of bark and ambrosia beetles are harmful to trees; these beetles also spread disease from tree to tree.

Blister Beetles (family Meloidae). Long, soft bodies. The body contains an oil that can cause a painful blister if it comes in contact with human skin. A number of species feed on garden and crop plants.

Bostrichid Beetles (family Bostrichidae). Bore into twigs and branches, where they feed.

Carpet Beetles (family Dermestidae).

Carrion Beetles (family Silphidae). Club-shaped antennae; legs adapted for digging. A common species is the sexton beetle (Necrophorus marginatus). Two sexton beetles will bury the entire carcass of a small bird or mouse in a few hours. The female lays eggs in a tunnel leading to the body, and both young and adults feed on the carcass.

Checkered Beetles (family Cleridae). Cylindrical bodies covered with hairs. Checkered patterns of color on forewings. Most prey on larvae of bark beetles.

Click Beetles (family Elateridae).

A click beetle throws its body into the air with a snapping movement.

Cucujid Beetles, or Flat Bark Beetles (family Cucujidae). Long, flat, small. Live under dead bark of trees. Most feed on mites and small insects.

Darkling Beetles (family Tenebrionidae). Hard-shelled with oval bodies. They live under rocks or loose bark and feed at night on dead or living plants. Some eat stored grain. The mealworm (Tenebrio molitor) is bred and sold as food for insect-eating pets.

Deathwatch Beetles (family Anobiidae).

Diving Beetles (family Dytiscidae). Flat, oval bodies that are dark and shiny. The beetles hang head downward from the surface of quiet ponds, waiting to catch insects. By holding a supply of air under their wing covers, they can breathe under water.

How Do Diving Beetles Breathe Underwater?

Desert beetles dive into the sand to keep cool. Diving beetles dive into the water to hunt for snails, tadpoles, and small fish.

The diving beetle is one kind of water beetle that lives in ponds and streams. It has a long, oval body good for floating and diving. Its long legs move together like oars as it swims through the water.

A bubble of oxygen is trapped under its elytra or body hair when it dives. This allows the diving beetle to breathe underwater for a long time. The diving beetle sometimes hangs upside down in the water. This allows it to draw more oxygen into its body through openings between its elytra and abdomen.

Dried-fruit Beetles, or Pollen Beetles (family Nitidulidae). Small, flat bodies. Feed mainly on dried or rotten fruit. A few species are serious pests.

Fireflies (family Lampyridae).

Ground Beetles (family Carabidae). Long, flattened bodies. Fast runners. Ground beetles usually hide under stones during the day. They destroy harmful insects.

Hister Beetles (family Histeridae). Small, dark, shiny bodies. Live in or under cow dung, in decaying matter, or under loose bark. Prey on other insects.

Ladybugs, or Ladybirds (family Coccinellidae).

Leaf Beetles (family Chrysomelidae). Oval bodies. Feed on leaves. Some species, including potato beetles, are very destructive. Many species are beautifully colored; among these species are tortoise beetles, some of which are iridescent gold.

Long-horned Beetles (family Cerambycidae). The threadlike antennae are sometimes larger than the body itself. Feed on pollen, leaves, and bark. May ruin wood articles by tunneling through them.

Metallic Wood-borers, or Jewel Beetles (family Buprestidae). Metallic blue or bronze bodies; serrated antennae. Attack a variety of trees, including apple trees and other fruit trees.

Patent-leather Beetles, or Bessbugs (family Passalidae). Large, shiny, black. Live in rotting logs. Eat decaying wood. Make squeaking sounds when disturbed.

Powder Post Beetles (family Lyctidae). Reddish brown. Bore out the insides of wooden objects, which they reduce to a powder. Very destructive.

Rove Beetles (family Staphylinidae). Long and flat. Live on the ground and scavenge for food. Some species make their homes in ant or termite nests.

Scarab Beetles (family Scarabaeidae). Some species are among the largest of insects. Rhinoceros and ox beetles reach a length of two inches (5 cm) in North America.

Seed Weevils (family Bruchidae).

Sexton Beetles. See Carrion Beetles in this list.

Snout Beetles, or Snout Weevils (family Curculionidae).

Soldier Beetles (family Cantharidae). Resemble mostly fireflies. Typically feed on aphids and other small insects.

Spider Beetles (family Ptinidae). Tiny, dark-colored bodies. Typically feed on stored products.

Stag Beetles (family Lucanidae). Have long mandibles, or jaws, which often are branched like antlers. Stag beetles look fierce but eat only vegetable matter and honeydew.

Tiger Beetles (classified in the family Cicindelidae by some biologists; in the ground beetle family by others). Long legs and sharp, powerful jaws. Tiger beetles hunt other insects, which they grab in their jaws and bang against the ground to kill.

How Ferocious Is the Tiger Beetle?

Like the big cat it is named for, the tiger beetle is a ferocious predator that eats other insects. But the tiger beetle’s larva is even more ferocious.

The wormlike larva lives in a burrow in the ground. It uses hooks to hang onto the wall of the burrow. Then it waits. When another insect comes close to the burrow, the larva attacks. It jumps out and sinks its jaws into its prey. Then it drags the helpless insect into its burrow and eats it.

Water Scavenger Beetles (family Hydrophilidae). Black or brown oval bodies; club-shaped antennae. Feed on decaying animal or vegetable matter.

Weevil.

Whirligig Beetles (family Gyrinidae). Black, oval bodies. Swarms of them are often found whirling about on the surface of lakes and streams.

Why Do Whirligig Beetles Spin?

When the whirligig (HWUR lee gihg) beetle sees prey, it spins around quickly to catch it. The whirligig beetle is another kind of water beetle. Its dark, oval body is well equipped to float. Its paddle-shaped hind legs help it skim and spin across the water.

The whirligig beetle has compound eyes that are divided in two. The upper half of each of its eyes sees on or along the water. The lower half sees underwater and looks for small fish and insect larvae to eat.

On a pond, you might see as many as a hundred whirligigs spinning around in zigzag patterns. But never once will one whirligig bump into another. A special organ in its antennae “picks up” echoes of sound waves bouncing off objects in the water. This helps the whirligig avoid collisions.

Beetle Talk

Does the Elephant Beetle Have a Trunk?

No, but it does have horns—five of them—that look like tusks. The elephant beetle is a member of the scarab family, and it is one of the largest beetles in the world. It uses its horns to defend its food source, which is the flowing sap from wounds in tree limbs.

The elephant beetle lives in the rain forests of Central and South America. The heat and moisture there help produce the largest beetles in the world. Other large-horned beetles from the tropics include the rhinoceros beetle, the Atlas beetle, and the Hercules beetle. These last two are named for a Greek god and a Greek hero, both known for their great strength.

What Is the World’s Heaviest Insect?

The supersized Goliath beetle of Africa is the world’s heaviest insect. This beetle can weigh as much as 3 1/2 ounces (99 grams) or more. This beetle is named for the giant in the Bible who was killed in battle by the shepherd boy David.

Like the giant Goliath, the Goliath beetle is big and awkward. When this beetle flies, it has a hard time staying airborne in rough weather. It twists and turns its legs while flying to keep its balance. This action is similar to the way a top spins to remain upright.

How Do Stag Beetles Use Their “Antlers”?

Stag beetles have horns like Goliath beetles, but they are set on either side of the head. The horns look like the antlers of a stag, a male deer. They are actually the beetle’s mandibles (MAN duh buhlz), or jaws. The antlers of some beetles are almost as long as their bodies.

Stag beetles use their antlers to fight other males for females. The males lock horns to see which is the stronger beetle. The winner often tosses its rival into the air. Then the winner may carry off the female as its prize. Only a few stag beetles can use their mandibles to pinch or bite. The others are harmless to humans.

How Do Desert Beetles Beat the Heat?

Desert beetles are well adapted to their hot, harsh environment. They are wingless and unable to fly. To get away from the hot sun, they dive deep into the sand. Below the surface there is more moisture. There are also cooler temperatures. When the sun sets, the desert cools down, and the desert beetles pop out of the sand. Then they begin their nightly hunt for food.

Some desert beetles have arched elytra. There is a space inside for air. This air pocket helps protect them from the heat.

This Namibian (nuh MIHB ee uhn) desert beetle of southern Africa has long, stiltlike legs. When the sand gets hot, the beetle rises up on its legs. This keeps its body as far away from the hot sand as possible.

Why Do Some People Think Beetles Are the Greatest?

People have found many uses for beetles. Ladybugs and other beetles are important pest controls for plant-eating insects. Jewel beetles and weevils get rid of fast-growing weeds. The beetles lay eggs on the weeds, and their larvae eat away at it.

Beetle shapes and designs are used in the jewelry that is popular in many parts of the world. The bodies and elytra of dead beetles have themselves been made into jewelry. In Mexico, live beetles are decorated with glass beads, fastened to small chains, and actually pinned to a person’s clothing.

Some people, however, would rather eat beetles than wear them. In parts of Asia, Africa, and Australia, beetles and beetle larvae are favorite foods.

How Are Beetles Good Environmentalists?

Beetles do far more to protect the environment than most people imagine. They are excellent recyclers. Beetles bury dead animals and plant material. By doing this, beetles help enrich the soil.

Tumblebugs and other dung beetles remove animal dung from the earth’s surface. This increases pastureland and prevents disease from spreading from flies and other insects that lay eggs in the dung.

Are Beetles in Danger?

As land becomes developed, some beetles are losing the forests and waterways they live in. Predators such as rats and birds eat other beetles into extinction. In turn, the beetles that live on the dead bodies of certain animals have no food to eat when these animals disappear from their habitat.

The Endangered Species Act (ESA) of 1973 was set up to protect all endangered animals, including beetles. Twelve species of beetles are protected by the ESA in the United States, including the northeastern beach tiger beetle. Any person who harms one of these beetles or its habitat can be fined or arrested.

But this kind of protection is often not enough. Some endangered beetles are raised in laboratories. Later, they may be released back into the wild.