The Life Cycle of Beetles. Kinds 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, pad like 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.

The life cycle of a beetle. A beetle goes through four stages of development: (1 ) egg, (2) larva, (3) pupa, and (4) adult. The illustration below shows the development of a broad-nosed beetle. The egg, laid in the ground, hatches into a larva. As the larva grows, it sheds its outer skin several times before becoming a pupa. The adult organs develop in the pupa. When this process is complete, the adult emerges

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 1 50 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.

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.

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 hook like 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, ring like body segments. These larvae are commonly called wire-worms. The larvae of some species eat the roots and seeds of crop plants.

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 ladybeetles, 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, species of ladybugs gather in large numbers to hibernate under leaves at the base of trees, under stones, or in debris.

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.