A side-profile of a male Hercules beetle, isolated on a white background

The Hercules beetle is one of two species that could be considered the world's biggest beetle © Udo Schmidt via Flickr (CC BY-SA 2.0)

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How big can beetles get?

There are roughly 400,000 species of beetle known to science, from miniscule insects less than half a millimetre long to giants longer than a chihuahua. 

Beetles - a group of insects also known as Coleoptera - make up more than a quarter of all known animal species on our planet. Many of these insects play important roles in their ecosystems.

While we may often think of beetles, such as ladybirds, as relatively small, there are some species that are truly enormous.

What is the longest beetle in the world?

There are two species that could be considered the world's longest beetle.

If you take total length into account, the Hercules beetle (Dynastes hercules) is the longest species of beetle in the world. Male Hercules beetles reach up to 19 centimetres long, about the same length as a new pencil and nearly 20 times the size of the common seven-spot ladybird that is found in the UK.

More than half of its length comes from exceptionally long, plier-like horns. These are used in battle against other males for access to females.

Hercules beetles are found from southern Mexico to Bolivia, as well as on some Caribbean islands. Adults mainly feed on rotten fruits that have fallen to the floor of their rainforest homes, while the larvae feed on dead wood. 

Side-by-side comparison of a Hercules beetle and Titan beetle

Titan beetles and Hercules beetles are the two the biggest species in the group of insects known as Coleoptera

If you consider body length alone, however, the titan beetle (Titanus giganteus) is the longer species. These giant insects may look a bit like a cockroach, but they are a species of longhorn beetle - a name that refers to this group's particularly long antennae.

Titan beetles reach 16.7 centimetres long and are found close to the equator in some of South America's hottest tropical jungles. These beetles have exceptionally strong jaws, sharp defensive spines and the ability to hiss by expelling air through the breathing holes (spiracles) along their sides.

A Titan beetle

Titan beetles look a bit like cockroaches, but are actually a type of longhorn beetle

What is the heaviest beetle in the world?

The heaviest beetles in the world are a group of rhinoceros beetles called Megasoma. These animals are found in South and Central America.

The Actaeon beetle (Megasoma actaeon) is the heaviest species. It is at its heaviest during the larval stage, which can last for three years. The heaviest Actaeon beetle larvae have tipped the scales at over 200 grams, about the same weight as a Syrian hamster. 

An Actaeon beetle larva

Actaeon beetles are the heaviest beetles in the world, reaching their greatest weight during their larval stage © MOROROPHOTO via Flickr (CC BY-NC-ND 2.0)

Goliath beetles (Goliathus) from Africa are often noted as being among the heaviest beetles, however in their larval stage they weigh 80-100 grams, and as an adult only about half that.

What is the biggest beetle in the UK?

The European stag beetle (Lucanus cervus) is the biggest beetle species found in the UK. It is mostly found in southeast England but is quite rare.

Females grow to about five centimetres long, whereas males have large mandibles and can reach 7.5 centimetres. 

A stag beetle specimen with its wings spread out

The European stag beetle is the biggest beetle species found in the UK

When they hatch, stag beetle larvae spend up to six years feeding on the rotting wood the female laid her eggs in. When the larvae pupate and transform into adults, they then feed only on tree sap and live for about eight weeks.

There are about 1,500 known species of stag beetle living around the world. They get their name from their mandibles, which resemble the antlers of stags.

Which beetle species has the longest snout?

Weevils are also known as snout beetles, so it is perhaps no surprise that one of these insects is the owner of the longest snout for a beetle.

The South African cycad weevil (Antliarhinus zamiae) also known as the horn-nosed weevil, has the longest rostrum relative to its body size. Its body is only about one centimetre long, with a snout that can add an extra two centimetres. 

An Antliarhinus zamiae specimen in a tray of weevils

The South African cycad weevil has the longest snout of any beetle

Like most other female weevils, the long snout of female A. zamiae beetles is used to drill holes in plants, in this case cycad seeds, to then lay its eggs. Male cycad weevils have much shorter snouts.

Which beetles display the most extreme sexual dimorphism?

A lot of animals exhibit sexual dimorphism - where the male looks different to the female - such as in size, weight, or colour.

Guinness World Records holds that the beetles that express the greatest sexual dimorphism are trilobite beetles (Platerodrilus sp). Female trilobite beetles are up to eight centimetres long and wingless, with spiny, armoured plates. Their male counterparts look quite different, in some species reaching a length of only 0.5 centimetres long and having the ability to fly.

A female trilobite beetle was first found in the 1800s, but it was not until the 1920s that the distinctly different males were finally identified. 

A male and female trilobite beetle

Trilobite beetles are named for the female's similarity in looks to an extinct group of arthropods © Tiia Monto via Wikimedia Commons (CC BY-SA 3.0)

Trilobite beetles belong to a family called Lycidae, a group known as net-winged beetles. Females of this group are typically larger than males.

The beetles are named for the female's similarity in looks to a now-extinct group of arthropods called trilobites, which died out about 250 million years ago.

Which beetle has the biggest family?

There are an estimated 83,000 species of true weevil (Curculionidae), making them the largest taxonomic family of beetles. About 480 species of weevil can be found in the UK.

A tray of weevil specimens

True weevils are the largest taxonomic family of beetles

Several weevil species are considered pests due to their ability to damage crops and stored food. You may have encountered the tiny wheat weevil (Sitophilus granarius) in bags of grain, for example.

Weevils are very diverse, however. There is a wide variety of sizes among the many species, and some are incredibly colourful. Almost all weevils are herbivores and many of them have very limited or only one host plant species.