Beetle is one of the most common of all insects. There are about 300,000 species (kinds) of beetles. They live everywhere on Earth except in the oceans. Beetles are found in rain forests and in deserts. They live in freezing cold areas and in hot springs. They inhabit mountain lakes and can even survive in polluted sewers.
Beetles have typical insect body parts, including antennae, three pairs of legs, and a tough exoskeleton (external skeleton). However, unlike other insects, adult beetles have a pair of special front wings called elytra. These wings form leathery covers that protect the beetle’s body and delicate hind wings. Because of their shell-like skeleton and hard wing covers, beetles have been called the “armored tanks” of the insect world.
Beetles vary greatly in shape, color, and size. Some, such as click beetles and fireflies, are long and slender. Others, including ladybugs, are round. Most beetles are brown, black, or dark red in color. But some have bright, shiny, rainbow colors. The smallest beetles, feather-winged beetles, measure less than 1/50 inch (0.5 millimeter) long. One of the largest beetles is the Goliath beetle of Africa. It grows about 5 inches (13 centimeters) long and weighs over 11/2 ounces (42 grams).
Most species of beetles are solitary insects—that is, they live alone and have no family life. The young develop without help from their parents. A few species of beetles are social insects. These beetles spend at least part of their life in family groups.
Beetles have many enemies, including birds, reptiles, and other insects. Most beetles protect themselves from enemies by hiding or by flying away. A few beetles produce bad-smelling chemicals that discourage attackers. Some beetles can bite.
Many beetles are pests because they feed on farm crops, trees, or stored food. But some beetles are helpful to people. For example, ladybugs and certain other beetles save crops by eating insect pests. Other beetles are important because they eat dead plants and animals and thus remove them from the environment.
The bodies of beetles
Like other insects, beetles have a body that is divided into three main parts. These parts are: (1) the head, (2) the thorax, and (3) the abdomen.
The head
includes the beetle’s mouthparts, eyes, and a pair of antennae. The eyes and antennae are the insect’s chief sense organs.
Mouthparts.
Beetles have chewing mouthparts. In beetles called weevils, the mouthparts are part of a long snout. A beetle’s jaws are called mandibles. A number of beetles have large, pincerlike mandibles.
Eyes.
Beetles have a compound eye on each side of the head. Each eye consists of a bundle of tiny, light-sensitive lenses. Each lens contributes a small bit of the total image that a beetle sees. Most beetles see motion and colors quite well. A few species are blind.
Antennae
vary greatly among beetles. Many beetles have antennae made up of threadlike or beadlike segments. In many of these beetles, the tip segments of the antennae are club-shaped. Some beetles have elbow-shaped or featherlike antennae. A beetle’s antennae are covered with hairs and special organs that can detect specific odors. Some beetles have special sense organs near the base of the antennae that provide a simple type of hearing. These organs send messages to the brain when certain sounds vibrate the antennae.
The thorax
forms the middle of the beetle’s body. It consists of three segments, each with a pair of legs. The second and third segments each have a pair of wings.
Legs.
Each leg of a beetle has five segments and claws at the end. Most beetles that are fast runners have long, slender legs. Other beetles have short, stout legs, often with flat pads on the bottom. These pads have hundreds of expanded hairs that act like suction cups and enable the beetle to walk upside down on slick surfaces. The legs of digging beetles have toothlike projections that are used to scrape away soil. Most swimming beetles have flattened hind legs. In some species, these legs are fringed with long hairs to form paddles.
Wings.
A beetle’s front wings, the elytra, are attached to the second segment of the thorax. The hind wings are attached to the third segment. In most species, the elytra cover the hind wings when the insect is not flying. To fly, a beetle pops open the elytra and holds them upward and outward so it can move its hind wings freely.
The abdomen
contains the reproductive organs and the chief organs of digestion. It typically consists of 10 segments, though only 5 to 8 segments may be visible. The segments are usually soft on the upper surface where they are covered by the elytra. The undersurface is harder for protection. Each segment of the abdomen has a pair of tiny holes called spiracles. Oxygen enters the beetle’s body through the spiracles.
The life cycle of beetles
A beetle passes through four stages of development during its life: (1) egg, (2) larva, (3) pupa, and (4) adult. The beetle changes greatly in appearance and structure from one stage to another. This process of development through several stages is called metamorphosis.
The egg.
Most female beetles lay eggs with oval shapes and drab colors. A female beetle may lay from a few to several thousand eggs at one time, depending on the species. Most beetles place their eggs on the surface of their food or inside cracks or holes. Eggs laid in the spring or summer may take a week to a month to hatch. Some species lay eggs in the fall. The eggs of these beetles hatch the following spring.
The larva
of a beetle is often called a grub. This form of the insect looks much different from the adult and may eat different food. Most larvae are wormlike, but some look like tiny lizards. In most species, the larval stage lasts from a few weeks to a few months. The larvae of some June beetles may take five years to mature.
As a beetle larva grows, it completely fills its rigid exoskeleton. It then breaks out of the exoskeleton while forming a new, larger one. This process is known as molting. Beetle larvae molt from three to seven or more times, depending on the kind of beetle.
The pupa.
When the larva molts for the last time, it transforms into a pupa. The pupa resembles an adult, but it is softer and different in color. In addition, the pupa has only small, padlike wings. Most beetles spend the pupal stage underground. This stage may last from a few days to an entire winter, depending on the species. During this time, adult organs form. When this process is complete, the pupa molts and the adult emerges.
The adult
has a short life and so must mate quickly. After mating, the female must find a place to lay her eggs. Most adults live for several weeks or months.
Kinds of beetles
Beetles make up the insect order Coleoptera. Coleoptera is a Greek word meaning sheath wings. It refers to a beetle’s elytra, which form a sheath (cover) for much of the upper body. The order Coleoptera is the largest order of insects. Nearly 40 percent of all insect species belong to it. The order is divided into about 150 families. This section describes some of the major beetle families. The scientific name of the family appears in parentheses after the common name.
Weevils
(Curculionidae), also called billbugs and snout beetles, consist of more than 40,000 species. They are the largest family of beetles. The mouthparts of adult weevils are at the tip of a long snout used to bore into fruits, seeds, and other plant parts. The larvae are legless and feed inside fruits and nuts or are borers. Many weevils are serious crop pests. Adults and larvae cause great damage by eating cotton bolls (seed pods). Most weevils are brown or gray, but some tropical species are brightly colored. See Boll weevil; Weevil.
Leaf beetles
(Chrysomelidae) total more than 25,000 species. Most leaf beetles can fly. When disturbed, however, many drop to the ground and play dead. Both the larvae and adults eat leaves and are serious crop pests. The Colorado potato beetle is one of the most common pests. It causes much damage to potato crops. See Potato beetle.
Ground beetles
(Carabidae) number more than 20,000 species. The adults have long legs and long antennae. Most species hide during the day and search for food at night. Both the adults and larvae prey on other animals. Some species of ground beetles have been brought to the United States to prey on crop-eating insect pests. The bombardier beetle is an unusual ground beetle. It defends itself by squirting two chemicals from the end of its body. The chemicals mix to produce a hot puff of gas that can repel an enemy.
Rove beetles
(Staphylinidae) make up more than 20,000 species. Rove beetles have unusually short elytra, which make them look like other insects called earwigs. Earwigs, however, have sharp pincers at the tip of the abdomen. Some rove beetles turn up the tip of their abdomen as if they could sting. Most larvae and adults prey on other animals or eat dead or decaying materials. Some species live on fungi or mosses.
Scarabs
(Scarabaeidae) consist of about 20,000 species. Dung beetles and tumblebugs are scarabs. They feed on dung (solid body wastes of animals). They can shape a mass of dung into a ball and bury it in soil. Females lay one egg in the ball of dung. Junebugs and Japanese beetles are two types of scarabs that eat crop plants. See Japanese beetle; Junebug; Scarab. Loading the player...
Dung beetle
Click beetles
(Elateridae) total about 8,000 species. These long, slender beetles jump or make a clicking sound if disturbed. They do this by means of a hooklike part that locks the first and second segments of the thorax. By building up pressure between these two body segments and then releasing the hook, a sudden body jerk and clicking sound is produced. Adult click beetles are commonly attracted to lights at night. Most larvae of click beetles are slender and have hard, ringlike body segments. These larvae are commonly called wireworms. The larvae of some species eat the roots and seeds of crop plants. See Click beetle.
Predacious diving beetles
(Dytiscidae) make up about 4,000 species. They live in bodies of fresh water. They prey on snails, tadpoles, and small fish. The larvae, which also live in the water, have long, soft bodies. The adults swim by moving their hind legs together like oars. When under water, the adults breathe air trapped in their body hairs or beneath their elytra.
Ladybugs
(Coccinellidae), also called ladybirds and lady beetles, number more than 4,000 species. Adult ladybugs have round bodies. Many are red, orange, or yellow and have black spots. The larvae look like miniature lizards, and some are brightly colored. Both adults and larvae eat insects that attack trees, shrubs, and fruit and vegetable crops. In the fall, some species of ladybugs gather in large numbers to hibernate under leaves at the base of trees, under stones, or in debris. See Ladybug.
Fireflies
(Lampyridae), also called lightning bugs, total about 1,900 species. Most species produce a cool, chemical light in the abdomen through a process called bioluminescence. The fireflies produce this light to find one another during mating. Each species uses a special pattern of flashes to identify each other. Some adult fireflies do not feed. Others eat pollen or nectar. The larvae prey on snails and insects. The glowing larvae and the flightless females of some species are often called glowworms. See Firefly.
