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Ground beetle

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Ground beetles belong to the family Carabidae, a massive group of insects. They are part of the suborder Adephaga, which is an ancient group of beetles. As of 2015, Carabidae was one of the 10 most species-rich animal families. There are more than 40,000 known species across the entire world. About 2,000 of these species live in North America. Around 2,700 species are found in Europe.

Most ground beetles are carnivores, meaning they hunt and eat other animals. Many species are active hunters that search for invertebrate prey. Tiger beetles, in the group Cicindelinae, are famous for their speed. They are among the fastest land animals on Earth relative to their body length. Unlike most ground beetles, tiger beetles are diurnal, meaning they hunt during the day. They use large eyes to find prey through sight.

Tiger beetle Lophyra sp.
Tiger beetle Lophyra sp.

To stay safe, many ground beetles use chemical defenses. They have paired pygidial glands in the lower back of their abdomen. These glands produce noxious or caustic secretions to stop predators. In the Brachininae lineage, these are called bombardier beetles. They mix secretions with volatile compounds to create a small combustion. This results in a loud popping sound and a cloud of hot, acrid gas. This gas can injure small mammals like shrews or kill invertebrate predators.

Brachinus spPCCA20060328-2821B
Brachinus spPCCA20060328-2821B

Some beetles have developed very specialized ways to defend themselves. The Anthiini tribe can mechanically squirt secretions over long distances. They can even aim these sprays with great accuracy. In Afrikaans, these beetles are known as "eye-pissers." Other beetles, like the genus Promecognathus, have specialized diets. They hunt cyanide millipedes, which are poisonous to most other animals. These beetles have evolved to counter the hydrogen cyanide used by the millipedes.

Ground beetles have a long history in science and human culture. During the early to mid-19th century, England experienced a "beetle craze." People paid high prices for rare and exotic specimens. The famous scientist Charles Darwin was an ardent beetle collector. When he was 20, he preferred searching for beetles over studying theology. Darwin even shared a story about a painful encounter with a beetle. He was holding two beetles when a Panagaeus cruxmajor attacked him. He tried to hold one in his teeth, but the beetle squirted acid down his throat.

Panagaeus cruxmajor bl
Panagaeus cruxmajor bl

Many ground beetles are beneficial to humans because they eat pests. The genus Calosoma includes "caterpillar hunters." These beetles eat large amounts of caterpillars, such as the tussock moth or woolly worms. In 1905, forest caterpillar hunters were shipped to New England. This was a form of biological control for the gypsy moth. However, some species can be a nuisance. The genus Zabrus contains herbivorous beetles that can damage grain crops. Large Carabinae species can also spoil food while camping by releasing defensive chemicals.

The evolution of these beetles is very old. The Adephaga suborder has been documented since the end of the Permian period. Ground beetles specifically evolved during the late Triassic period. They had already separated from their closest relatives by 200 million years ago. The family continued to diversify throughout the Jurassic period. Later, more advanced groups like the Harpalinae underwent a large radiation during the Cretaceous. Today, scientists use phylogenomic analyses to study these complex evolutionary patterns.

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🖼️ Images & Media (4)
File:Panagaeus cruxmajor bl.jpg
Panagaeus cruxmajor bl.jpg
Lebia tricolor.webm
File:Brachinus spPCCA20060328-2821B.jpg
Brachinus spPCCA20060328-2821B.jpg
File:Tiger beetle Lophyra sp..jpg
Tiger beetle Lophyra sp..jpg
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