Beetles shape ecosystems through what they eat

Beetles play a major role in ecosystems, and even the diet of a single small beetle can influence the natural world, entomologist Leif-August Kirs told ERR’s Vikerraadio programme “Ökoskoop.”

More than 400,000 beetle species have been described worldwide. Beetles account for about 40 percent of all insect species and roughly a quarter of the entire animal kingdom, Kirs said. Estonia is home to slightly more than 3,000 known beetle species, although the actual number is likely between 3,000 and 4,000.

The world’s largest insects are beetles, including tropical species that can grow to nearly 20 centimetres long. In Estonia, beetles can reach up to four centimetres.

Although beetles live everywhere around people, both indoors and outdoors, in water and in forests, many are rarely seen. Some are nocturnal, while others are so closely tied to specific habitats that they seldom leave them. They may live inside wood, in moss litter or in animal carcasses, Kirs said.

When people think of a beetle, they may picture a ground beetle, which is slightly elongated and has thread-like antennae and long legs. These beetles move quickly because they are predators and must catch their prey.

Kirs also explained that scarabs are beetles, but not every beetle is a scarab. Beetles are complete-metamorphosis insects, meaning that their eggs hatch into larvae that look entirely different from the adults rather than into miniature beetles.

Some beetles feed on dead material and act as decomposers. They are often so small that people do not notice them, and even experienced insect researchers may need to take specimens to a museum and examine their features under a microscope to identify the species. In some cases, females cannot be identified because the process relies on examining male genitalia, Kirs said.

Dung beetles are among the strongest insects. They can move pieces of dung much larger and heavier than themselves away from a large dung pile, where competition is intense. Some carry a large piece away, while others transport it by rolling it.

Some beetles live alongside people because they are attracted to stored food and textiles. A large black beetle found among dry goods may be a mealworm beetle, whose larvae feed on flour. Insects can also enter through extremely small gaps, Kirs said.

People depend on food grown in the soil and on clean, fertile land, which are products of the wider web of life. Beetles are an important part of that ecosystem, even when their role is not conspicuous, Kirs said. In undisturbed forests and meadows, hundreds of plant species can coexist, while landscapes altered by people are often dominated by a single plant.