Beetles: What to Know

Medically Reviewed by Jabeen Begum, MD on January 13, 2023
8 min read

Beetles are a very diverse category of insect with about 400,000 known species in the world. Beetles live nearly everywhere and eat almost everything. You will likely encounter beetles frequently in your lifetime — but it doesn’t always have to be a bad experience.

The word “beetle” comes from an old English word that means “little biter”. They are insects that belong to the largest order in the animal kingdom — Coleoptera — which means “folded wing” or “sheathed wing”.

Beetles are everywhere. Approximately one-fourth of all animal species known to science are beetles and there are about 30,000 known species in the United States and Canada alone. Scientists estimate there are millions more species of beetles yet to be discovered.

The beetle life cycle varies from species to species, but there are also many similarities. All beetles have four life stages:

1. Egg. Female beetles will lay hundreds of tiny yellow or white roundish eggs, which take four to 19 days to hatch.  Some females lay eggs under leaves or in rotten wood, in underground structures made of dung, or inside leaves that they rolled up themselves. A few beetle species don’t lay eggs but keep them inside the female’s body and give birth to live larva.

2. Larva. In the larval stage, the young beetles eat and grow, shedding their exoskeleton as they get bigger. Most beetles have three to five larval stages, but it can vary from one to stages, depending on the species.

3. Pupa. The pupa stage is an immobile, non-feeding stage that usually lasts over winter. In most species, an adult beetle emerges after up to nine months.

4. Adult. Adult, fully formed beetles will feed, mate, and the female will lay eggs, continuing the life cycle. Most beetles live for about a year, but some bigger species live much longer.

Most beetle species are active at night, but some have special protection and are active during the day.

Beetles have a variety of defense mechanisms:

  • Camouflage: blending into the background, so predators don’t see them. Leaf beetles are green like leaves, and some weevils look like bird dung.
  • Mimicry: looking like something else, so predators avoid them. Longhorn beetles look like wasps, which carry a painful sting.
  • Toxicity: some beetles secrete a substance that tastes bad or can even be poisonous. Ladybirds and blister beetles do this. Many toxic beetles are also brightly colored to warn predators to stay away.
  • Attack: Some beetles have adaptations that can help them with their physical defense. Longhorn beetles can pinch with mandibles, and bombardier beetles spray acid.

Beetles are insects, which means they all have the same body structure: head, thorax, abdomen, and six legs. Beetles also have two wing pairs. The outer ones are smaller and are complex, often for protection, while the inner ones are used for flying in many species.

Most beetles are dark colors like brown or black, but many are bright colors. They vary significantly in size and shape.

With potentially millions of species of beetles, we can’t cover all of them. Here are some of the main types of beetles you may encounter:

Lady Beetles. Also called ladybugs or ladybirds, these beetles are usually spotted and bright. There are about 5,000 species that become active in spring and eat a lot of aphids that damage crops and gardens.

Ground Beetles. Generally dark and relatively large, there are at least 34,000 ground beetle species. They like damp soil and logs and can be found hidden under plants.

Rove beetles. This is a large, diverse group with shorter primary wings. They are mostly nocturnal and associated with soil.

Fireflies. Also called lightning bugs, fireflies use flashing lights for mating. Many of them feed on slugs and worms, and they prefer damp, dark environments.

Soldier Beetles. These beetles have elongated bodies and are often found on flowers. Some species are predatory, while others are omnivorous. There are 4,500 known species of soldier beetles.

Bark Beetles. There are several species living in western forests and urban environments. Though normally part of a healthy ecosystem, bark beetle outbreaks sometimes lead to tree death and increased susceptibility to wildfire.

Leaf Beetles. These beetles are plant feeders and can cause a lot of damage to crops. Many species of leaf beetle vary a lot in shape and color. This group includes the Colorado potato beetle, cucumber beetle and flea beetles. Flea beetles are tiny, dark, and destroy leaves by eating holes in them. 

Scarab beetles. This group includes dung beetles, June beetles — also known as June bugs — and Japanese beetles. Japanese beetles are a common pest to gardeners and eat over 300 different species of plants. They can be invasive and tend to aggregate in large numbers. The scarab beetles group also includes large-sized Hercules beetles, rhinoceros beetles, and elephant beetles which can grow to six inches but are harmless.

Weevils. This is the largest beetle family, with 48,000 species worldwide. They eat plants and stored grains and are recognized by long snouts with long antennae.

Click beetle. These beetles click when righting themselves by snapping two parts of the body together and springing into the air. Click beetle larvae are called wireworms. They are destructive to gardens — especially root crops such as carrots and potatoes.

Longhorn beetles. These beetles have antennae at least half the length of their bodies. They are often large and brightly colored and feed on flowers, trees and plants.

Wood Boring beetles. These are also known as jewel beetles. They are often large and colorful. Some species bore into wood and are a common forest pest.

Beetles can adapt to nearly any environment and live everywhere — except the oceans and the Antarctic and arctic polar regions.

Beetles live in caves, under logs, in mud, in fungi, in decaying material, in deserts, in freshwater, and even in the nests of certain birds, mammals, termites, and ants. You may see many species of beetles, especially in places where dried food is stored, such as warehouses, pantries, and bakeries.

There are many, many types of beetles who have many, many kinds of diet. Beetles eat nearly everything. 

Here is a short list of things beetles eat, depending on the species:

  • other insects (other beetles, flies, mites, caterpillars)
  • worms
  • snails
  • crabs
  • plants (leaves, stems, roots, fruit, seeds)
  • wood (trees, furniture, house structures)
  • decomposing or dead things (rotten wood or plants, dead animals, dung)
  • fungi
  • some combination of these things

Because of the beetle life cycle, they tend to hatch many adults at once. This can cause beetle infestations at certain times of the year, usually the spring. A single beetle usually is not a problem.

Depending on the species of beetle, there may be different signs of a beetle infestation:

  • many beetles crawling around or bunched together. 
  • damaged wood structures. The larva of wood-boring beetles damage wood by making tunnels, and you may see a small pile of powdery wood dust.
  • dead or damaged plants especially leaves. Japanese beetles like to eat the leaves until they look like little leaf skeletons, and the larvae can cause dead grass patches.

Since beetles are nearly everywhere, you probably have them in your house, yard, or garden.  Your best bet is to remove the opportunity for beetles to feed and live in your home.

There are several ways you can work to prevent a beetle infestation in your house:

  • remove food leftovers 
  • store food in sealed containers
  • clean up crumbs
  • keep trash cans closed
  • store and seal pet food 
  • don't leave food bags open 
  • throw out expired food items
  • fix cracks around doors/windows 
  • prune trees/shrubs near the house
  • inspect new and used furniture
  • throw out damaged furniture

It is probably impossible to keep beetles out of your yard and garden, as they are part of the natural ecosystem. If you want to decrease their numbers, begin treating large beetle infestations early in the season.

Most beetles do not cause harm to people or pets directly. Most of the time, beetles cause harm by damaging property.

Beetles damage crops in both large-scale farms and smaller private gardens by eating leaves, roots, stems, seeds, and fruit. Some beetles can cause damage to trees — sometimes entire forests — by laying eggs in the bark where the larvae make tunnels. Other beetles cause damage to your house by eating or burrowing in wooden furniture, wooden parts of buildings, and food stores. Small hive beetles damage beehives in the southeastern United States.

Overall, beetles are not dangerous. Beetles don’t attack people, don’t suck blood, and don’t give people diseases.

A few species can bite but do not cause serious injury, such as Longhorn beetles and root borers. Other species are toxic, such as the blister beetle, or can spray toxic substances, such as the bombardier beetle.

Though many beetles are considered pests, some beetles are helpful.

Lady bugs eat aphids and smaller insects that damage gardens and crops. Just one adult ladybug can eat up to 5,000 aphids in its lifetime.

Like the better-known honeybees, beetles help flowering plants reproduce by spreading pollen. Beetles make up the largest group of pollinators in the world, pollinating 88% of the 240,000 flowering plants around the world.

Some species of beetles feed on the seeds of weeds and harmful plants, which helps agriculture crops grow and thrive.

There are various ways to get rid of beetles in your home, yard and garden: 

  • Neem oil. This is a natural repellent, safe for pets and children. Just sprinkle on doorways, windows, and directly on plants, but must do it often.
  • Peppermint oil. Similar to neem oil, peppermint oil is safe for pets/children. Just mix with water and spray on entry points. Some people may object to the strong smell of peppermint.
  • Lavender. Dried lavender flowers can be placed in drawers or mix oil with water and sprayed all over. Lavender is safe, and you can often use.
  • Insect traps. The scent attracts bugs, then traps them inside. Use where you see beetles crawling around. This may not be practical because you must frequently replace them.
  • Pyrethrin. This is a chemical made from chrysanthemum flowers, available in stores. It kills bugs by acting on the nervous system. It can be messy to clean up dead bugs.
  • Diatomaceous earth. This substance, made of fossilized and crushed algae, dehydrates insects until they die. Sprinkle it around entry points. It is safe for pets and children, but you must clean up dead bugs.
  • Physical removal. Using your gloved hands to pick the beetles from your garden plants is an option if there are not too many. 
  • Ignore them. The occasional beetle usually doesn’t cause too many problems, so learn to live with them. 
  • Traps and pesticides. Be sure to read and follow instructions, or they will be more trouble than they are worth. Bait stations can be toxic to pets and children.
  • Prevent entry. Don’t let beetles into your house. Seal off doorways, windows, and foundation cracks.
  • Professional exterminators. When in doubt and the beetles are causing huge problems, get professional help. Professional pest control companies know how to eliminate beetles without harming people and pets.

Flea beetles can be a particular problem for many types of crops. Start monitoring for large groups of beetles in the spring and take action early. Remove old crops and weeds they are attracted to, place crop covers, and use commercial insecticides if needed. 

With 400,000 known species of beetle and likely millions more to discover, you will likely see beetles around your house and yard. If you can, be kind and respect their place in the ecosystem. Beetles are arguably the most numerous, diverse, adaptable, and fascinating insects in the world.