Beetles inhabit nearly every ecological niche on the planet. This group includes some of our most beloved bugs, as well as our most reviled pests. Here are 10 fascinating facts about beetles, our largest insect order.

One out of Every Four Animals on Earth Is a Beetle

Beetles are the largest group of living organisms known to science, bar none. Even with plants included in the count, one in every five known organisms is a beetle. Scientists have described over 350,000 species of beetles, with many more still undiscovered, undoubtedly. By some estimates, there may be as many as 3 million beetle species living on the planet. The order Coleoptera is the largest order in the entire animal kingdom.

Beetles Live Everywhere

You can find beetles almost anywhere on the planet, from pole to pole, according to entomologist Stephen Marshall. They inhabit both terrestrial and freshwater aquatic habitats, from forests to grasslands, deserts to tundras, and from beaches to mountaintops. You can even find beetles on some of the world's most remote islands. The British geneticist (and atheist) J. B. S. Haldane is purported to have said that God must have an "inordinate fondness for beetles." Perhaps this accounts for their presence and number in every corner of this globe we call Earth.

Most Adult Beetles Wear Body Armor

One of the traits that make beetles so easy to recognize is their hardened forewings, which serve as armor to protect the more delicate flight wings and soft abdomen underneath. The famed philosopher Aristotle coined the order name Coleoptera, which comes from the Greek koleon, meaning sheathed, and ptera, meaning wings. When beetles fly, they hold these protective wing covers (called elytra) out to the sides, allowing the hindwings to move freely and keep them airborne.

Beetles Vary Dramatically in Size

As you would expect from a group of insects so numerous, beetles range in size from nearly microscopic to downright gigantic. The shortest beetles are the featherwing beetles (family Ptiliidae), most of which measure less than 1 millimeter long. Of these, the smallest of all is a species called the fringed ant beetle, Nanosella fungi, which reaches only 0.25 mm in length and weighs just 0.4 milligrams. On the other end of the size spectrum, the Goliath beetle (Goliathus goliathus) tips the scales at 100 grams. The longest known beetle hails from South America. The appropriately named Titanus giganteus can reach 20 centimeters long.

Adult Beetles Chew Their Food

That might seem obvious, but not all insects do so. Butterflies, for example, sip liquid nectar from their own built-in straw, called a proboscis. One common trait all adult beetles and most beetle larvae share is mandibulate mouthparts, made just for chewing. Most beetles feed on plants, but some (like ladybugs) hunt and eat smaller insect prey. Carrion feeders use those strong jaws to gnaw on skin or hides. A few even feed on fungus. Whatever they're dining on, beetles chew their food thoroughly before swallowing. In fact, the common name beetle is thought to derive from the Old English word bitela, meaning little biter.

Beetles Have a Big Impact on the Economy

Only a tiny fraction of the overall insect population can be considered pests; most insects never cause us any trouble at all. But because so many are phytophagous, the order Coleoptera does include quite a few pests of economic importance. Bark beetles (like the mountain pine beetle) and wood-borers (such as the exotic emerald ash borer) kill millions of trees each year. Farmers spend millions on pesticides and other controls for agricultural pests like the western corn rootworm or the Colorado potato beetle. Pests like the Khapra beetle feed on stored grains, causing more economic losses well after the harvest is completed. Just the money spent by gardeners on Japanese beetle pheromone traps (some would say money wasted on pheromone traps) is greater than the GDP of some small countries!

Beetles Can Be Noisy

Many insects are famous for their sounds. Cicadas, crickets, grasshoppers, and katydids all serenade us with songs. Many beetles produce sounds, too, although not nearly as melodic as those of their Orthopteran cousins. Deathwatch beetles bang their heads again the walls of their wood tunnels, making a surprisingly loud knocking sound. Some darkling beetles tap their abdomens on the ground. A good number of beetles stridulate, particularly when handled by humans. Have you ever picked up a June beetle? Many, like the ten-lined June beetle, will squeal when you do. Both male and female bark beetles chirp, probably as a courtship ritual and a means of finding one another.

Some Beetles Glow in the Dark

Species in certain beetle families produce light. Their bioluminescence occurs through a chemical reaction involving an enzyme called luciferase. Fireflies (family Lampyridae) flash signals to attract potential mates, with a light organ on the abdomen. In glowworms (family Phengodidae), the light organs run down the sides of the thoracic and abdominal segments, like tiny glowing windows on a railroad boxcar (and thus their nickname, railroad worms). Glowworms also sometimes have an additional light organ on the head, which glows red! Tropical click beetles (​family Elateridae) also produce light by virtue a pair of oval light organs on the thorax and a third light organ on the abdomen.

Weevils Are Beetles, Too

Weevils, easily recognized by their elongated, almost comical beaks, are really just a type of beetle. The superfamily Curculionoidea includes the snout beetles and various types of weevils. When you look at a weevil's long snout, you might assume they feed by piercing and sucking their meal, much like the true bugs. But don't be fooled, weevils belong to the order Coleoptera. Just as all other beetles do, weevils have mandibulate mouthparts made for chewing. In the case of the weevil, however, the mouthparts are usually tiny and are found just at the tip of that long beak. Many weevils cause significant damage to their plant hosts, and for this reason, we consider them pests.

Beetles Have Been Around for About 270 Million Years

The first beetle-like organisms in the fossil record date back to the Permian Period, roughly 270 million years ago. True beetles — those that resemble our modern-day beetles — first appeared about 230 million years ago. Beetles were already in existence before the breakup of the supercontinent Pangaea, and they survived the K/T extinction event thought to have doomed the dinosaurs. How have beetles survived for so long, and withstood such extreme events? As a group, beetles have proved remarkably adept at adapting to ecological changes.

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