Beetle

Beetles are interesting insects that belong to the group Coleoptera (/koʊliːˈɒptɛrə/). They are known for their hard front wings, called elytra, which protect their softer wings used for flying. Beetles are the largest group of insects, with about 400,000 known species. Scientists think there may be many more species still unknown.

Beetles live almost everywhere on Earth, except in the oceans and the polar regions. They help nature in many ways. Some eat plants or fungi, while others help break down dead plants and animals. Some beetles can harm crops, like the Colorado potato beetle, but many are helpful, such as Coccinellidae (ladybugs or ladybirds), which eat harmful insects like aphids.

Beetles come in many shapes, sizes, and colors. Some have short elytra, while others have softer ones. Many change a lot from their baby form, called larvae, to their adult form through a process called metamorphosis. Some beetles can even glow in the dark, like fireflies, using light to attract friends. Their hard outer shell, or exoskeleton, helps keep them safe.

Beetles have been important to people for thousands of years, from the sacred scarabs of ancient Egypt to today’s art and pets. Some people eat over 300 kinds of beetles, especially their larvae, such as mealworms. While some beetles can damage crops and forests, many others help by controlling harmful insects. The study of beetles is called coleopterology.

Etymology

The name "Coleoptera" comes from ancient Greek. Aristotle gave them this name because of their special hardened front wings called elytra. In English, the word "beetle" comes from an old word meaning "little biter." There is also an old English term for beetles, "chafer," which you can see in names like cockchafer.

Distribution and diversity

Beetles are the largest group of insects, with about 400,000 known species. They live in nearly every place on Earth, from tropical forests to places near roots underground.

Some of the largest beetles include the goliath beetle, which can be very heavy, and the Hercules beetle, which is the longest beetle known. The smallest beetle is the featherwing beetle, which is tiny—smaller than a grain of sand.

Evolution

Beetles have been around for a very long time. The oldest known beetle, named Coleopsis, lived about 295 million years ago in what is now Germany. Early beetles mainly ate wood and lived in places like Siberia, Europe, and the Ural mountains in Russia.

During the Jurassic period, around 210 to 145 million years ago, the number of beetle families grew quickly. Some beetles began eating plants, while others hunted other insects. By the Cretaceous period, beetles had spread all over the world, living in many different places, from forests to water. Today, beetles are one of the most diverse groups of insects on Earth.

Phylogeny

Beetles have many species, making it hard to sort them into groups. The largest group is called Polyphaga, with over 300,000 species. This group includes rove beetles, scarab beetles, blister beetles, stag beetles, and true weevils (Curculionidae). Another group, Adephaga, has about 10 families of beetles that mostly hunt other insects, like ground beetles and water beetles (Dytiscidae).

Scientists have studied beetles and found they all come from one common ancestor. Different groups of beetles appeared millions of years ago, with most families forming during the Cretaceous period.

External morphology

Beetles have a hard outer shell called an exoskeleton that helps keep them safe. Their front wings are hard and called elytra. They use these to cover their bodies instead of for flying. Most beetles have strong jaws called mandibles for eating and sometimes to protect themselves.

Beetles' bodies have three main parts: the head, the thorax, and the abdomen. Their legs end in small parts called tarsi. Many beetles have special claws on their legs. Some beetles, like water beetles, have legs for swimming. Others, like flea beetles, can jump with special leg parts. Beetle wings are usually hard for protection, but some can fly with their hind wings when they lift their elytra. The abdomen has small holes called spiracles for breathing.

Anatomy and physiology

Beetles have a digestive system made for eating plants. In some beetles that hunt other animals, digestion happens in a special part called the crop. Their nervous system has clusters of cells that control their movements and senses.

Beetles breathe through small holes in their bodies called spiracles. Air moves through tubes called tracheae, bringing oxygen and taking away carbon dioxide. Some beetles that live underwater carry a bubble of air to breathe. They have a simple system that moves fluids around their bodies. Certain beetles have organs that make smells to attract mates, and some, like fireflies, can produce light.

Reproduction and development

Beetles are insects that go through a process called complete metamorphosis. This means they have four main stages in their life: egg, larva, pupa, and adult. The larvae, often called grubs, are the main eating stage and can look very different from the adult beetles.

Some beetles have interesting ways of finding mates. For example, fireflies use light signals to attract each other. Others may use special smells or perform rituals before mating. Most beetles lay eggs at some point. The larvae grow and change several times before becoming pupae, and finally, they emerge as adult beetles.

Behaviour

Beetles have interesting ways to move and communicate. Their hard front wings, called elytra, help them fly and fit into small spaces. Some beetles can fly with their elytra closed, while others mainly walk on the ground. Aquatic beetles have special ways to keep air when underwater, like holding air under their bodies or carrying air bubbles.

Beetles use different methods to talk to each other, such as releasing special chemicals called pheromones. Some beetles can even make sounds to communicate or defend themselves.

A few beetle families take care of their young. For example, some rove beetles protect their eggs and larvae from danger, while burying beetles work together to care for their offspring. Most beetles, however, do not stay with their young after laying eggs.

Beetles eat many different things depending on where they live. Some eat plants, others eat animals, and many eat decaying matter like dung or dead animals.

Ecology

Beetles have many ways to protect themselves from animals that want to eat them. Some change their colors to blend in with their surroundings. Others look like dangerous insects to scare away predators. Many beetles produce bad-tasting or poisonous substances and have bright colors to warn off attackers.

Beetles also have special relationships with other living things. Some, like the ambrosia beetle, work with fungi to digest wood. The beetle makes tunnels in dead trees and grows fungus there, which provides food for both. Other beetles help plants by moving pollen from one flower to another while they feed.

Beetles can live in very cold or very hot places by changing their bodies. Some cold-weather beetles make special proteins that stop ice from forming inside them. Desert beetles can survive very hot temperatures and even collect water from fog using special surfaces on their wings.

Relationship to humans

In ancient cultures

Main article: Scarab (artifact)

Some types of dung beetles, like the sacred scarab, Scarabaeus sacer, were very important in Ancient Egypt. People thought the beetle symbol had deep meaning. The scarab was linked to Khepri, the god of the rising sun, because of how the beetle rolls its dung ball. Neighboring lands also used scarab shapes for seals. Writers from Plutarch mentioned beetles as a sun symbol. The Greek Magical Papyri included scarabs in spells.

Pliny the Elder wrote about beetles in his Natural History, describing the stag beetle. He said some insects have a shell (elytra) to protect their wings. Some big beetles have long horns they use for biting. The stag beetle appeared in an old Greek story told by Nicander and Antoninus Liberalis, where Cerambus changes into a beetle.

As pests

Many beetles eat plants and can damage crops. The boll weevil, which feeds on cotton, came to the United States from Mexico around 1892 and became a big problem for cotton farms. The bark beetle, elm leaf beetle, and the Asian longhorned beetle (Anoplophora glabripennis) attack elm trees and can spread sickness. Some beetles, like the Colorado potato beetle, have learned to resist insect-killing sprays.

As beneficial resources

Beetles can help control pests. Lady beetles eat aphids and other pests. Ground beetles eat many harmful insects and help control weeds by eating seeds. Dung beetles bury animal waste, which keeps flies away and makes soil healthier. The Australian Dung Beetle Project brought dung beetles to Australia to help control flies.

As food and medicine

People in many parts of the world eat beetles, usually the larvae, with about 344 species used as food. The mealworm and the rhinoceros beetle are commonly eaten. Some cultures use beetles in folk medicine to try to treat illnesses, but there is no scientific proof these work.

As biodiversity indicators

Because many beetle species are easily affected by changes in their home, scientists use them to check how healthy an environment is. Predatory beetles like tiger beetles (Cicindelidae) are good for this because they are easy to see and live in many places around the world.

In art and adornment

Beetles have been used in art and jewelry for a long time. Their hard wing covers, called elytra, are used to make beautiful things. In parts of Mexico, beetles of the genus Zopherus are turned into living brooches by adding jewelry and chains.

In entertainment

Some people enjoy watching fights between large beetles, especially in Chiang Mai, Thailand, where male rhinoceros beetles are trained to fight. In South Korea, a type of beetle is used in a game like roulette. Beetles have also been used as musical instruments, such as the "hugu" weevil in Papua New Guinea.

As pets

Some people keep beetles as pets. In Japan, keeping horned rhinoceros beetles and stag beetles is very popular, especially with children.

As things to collect

Collecting beetles was very popular during the Victorian era. Naturalists traveled far to find new species.

As inspiration for technologies

Further information: Biomimetics

Scientists study beetles to make new technologies. For example, the spray from the bombardier beetle has inspired a new kind of fine mist spray. The way the Namib desert beetle collects water has led to the design of a water bottle that fills itself. Some beetles have been used in experiments to see if they can be guided from far away, which could help with watching places.

In conservation

Because beetles are such a big part of the world's animals, keeping them safe is important. Some species are at risk because they live in special places that are disappearing. Conservationists work to teach people about beetles, using well-known species like the stag beetle and tiger beetles to interest people. In places like Japan and South Africa, loved beetles help bring more people to learn about nature and animals.