Beetle Larvae

Beetle larvae are the young stage of beetles, the part of life between hatching from an egg and turning into a pupa. Many people call them grubs. They often look like little worms, but each one will one day become a beetle.

Beetle larvae Quick Facts

Common name	Beetle larvae
Scientific name	Coleoptera
Kingdom	Animalia
Phylum	Arthropoda
Class	Insecta
Type	Insect (beetle larva)
Diet	Leaves, roots, wood, fungi, dung, fabrics or other animals, depending on species
Habitat	Soil, wood, plants, dung, water and sometimes homes
Native range	Worldwide except Antarctica
Size	From under 1 mm to over 10 cm, depending on species
Lifespan	Larval stage lasts weeks to several years
Special feature	Molts several times as it grows

A Quick Look at Beetles

Beetles belong to the order Coleoptera, which means “sheath wing” in Greek. Their hard front wings, called elytra, act like a protective case for the delicate flying wings folded underneath.

There are about 400,000 known kinds of beetles, and scientists keep finding more. That makes up about 40 percent of all known insects and around a quarter of all known animal species. Beetles live almost everywhere on land and in fresh water, except in the polar regions and the open ocean.

Where Larvae Fit in the Life Cycle

Beetles go through complete metamorphosis, which has four stages. First, adults mate and the female lays eggs, which is the start of the beetle life cycle. The eggs hatch into wingless larvae. The larvae later become pupae, which do not eat or move much. Finally, the adults come out, and the cycle starts again.

For many beetles, the larval stage is the longest part of life. It can last weeks, months or even several years.

How Beetle Larvae Grow

Beetle larvae have big appetites. They eat a lot so that they can grow fast. But their tough outer skin, called the exoskeleton, cannot stretch much. So, every so often, a larva must molt, or shed its old skin, and grow a new, bigger one.

The stages between molts are called instars. Most beetle larvae go through three to five instars, though some have more. By the end, a larva may be as big as, or even bigger than, the adult it will become.

Hypermetamorphosis

A few beetles change shape several times as larvae. This is called hypermetamorphosis. The young larvae of most blister beetles (Meloidae) hatch from eggs laid on or near flowers. They grab onto bees visiting the flowers and hitch a ride back to the bee nest. There, they change into a fatter, slower form and feed on the bee’s eggs and stored food.

What Do Beetle Larvae Look Like?

Beetle larvae look very different from adults. They have a hard head with chewing jaws, a soft body made of segments, and usually no visible wings. Their wings develop inside the body and only appear during the pupal stage.

A larva’s shape depends on how it lives. Predatory larvae, such as those of ground beetles, often have long, narrow jaws, long legs and slim bodies, so they can run fast and grab prey. Larvae that live inside wood or soil are often pale, soft and plump, with tiny legs or none at all. Scarab grubs, like those of June beetles, curl into a C shape.

What Do Beetle Larvae Eat?

Different larvae eat very different things. Some eat leaves, roots or seeds. Some tunnel through wood. Others feed on dung, dead animals or fungi. Many, like the larvae of ladybugs and ground beetles, are hunters that eat other small creatures.

Some beetle larvae live underwater in ponds and streams. A few of them have gills to take oxygen from the water, while others come up to the surface to breathe air.

How Beetle Larvae Defend Themselves

Many animals eat beetle larvae and adults, including birds, lizards, frogs and other amphibians, fish, dragonflies, ants, spiders, other beetles and mammals such as bats and shrews. To survive, beetles have many anti-predator adaptations.

Most larvae hide inside wood, soil or plants where predators cannot easily see them. Others are spiny or hairy, which makes them hard to swallow. Some carry bad-tasting chemicals. Ladybug larvae and adults have bright patterns that work as a warning to predators.

Larvae also face parasites. Some wasps lay their eggs on or inside beetle larvae, including longhorn beetle larvae deep in wood. When the wasp eggs hatch, the young wasps feed on the beetle larva.

Carpet Beetle Larvae

Carpet beetle larvae are the ones most often found in homes. They are small, about 3 to 5 mm long, and are covered in bristly brown hairs, which is why they are sometimes called woolly bears. Some, like the black carpet beetle larva, are smoother and shaped like a carrot, golden to chestnut brown.

They feed on natural materials such as wool, silk, fur, feathers and dead insects, so they can damage carpets, clothing and furniture. Their growth can take a few months or longer than a year, depending on warmth and food.

Carpet beetle larvae do not bite or spread disease, but their tiny hairs can make some people’s skin itchy. To get rid of them, vacuum often, especially along edges and under furniture, wash or dry-clean woolen items, and store clothes in sealed containers. If the problem continues, a pest professional can help.

Fun Facts About Beetles

• Beetles live on every continent except Antarctica.
• All adult beetles have chewing mouthparts, so they can eat solid food like leaves, seeds, wood and other insects.
• Some beetles are serious pests. Bark beetles kill millions of trees during big outbreaks.
• Fireflies are beetles. They make light using a chemical reaction with an enzyme called luciferase, and their larvae, called glowworms, can glow too.
• Beetle-like insects appear in fossils more than 270 million years old, long before the first dinosaurs. Beetles survived the mass extinction that wiped out the dinosaurs.

Why Beetle Larvae Matter

Beetle larvae may not be as pretty as adult beetles, but they are very important. They break down dead wood, dung and leaves, help recycle nutrients, control pests and feed many other animals. Next time you dig in the garden and find a grub, you will know it is a beetle in the making.

Related: bee larvae · carpet beetles · bed bugs

Beetle larvae FAQs