Beetles are a group of insects which are biologically classified in the order Coleoptera.
The word “coleoptera” is from the Greek, koleos, meaning “sheath”, and pteron, meaning “wing”, thus “sheathed wing.”
There are about 400,000 species of beetles; new species are discovered frequently.
They make up about 40% of all insect species so far described, and about 25% of all animals.
Beetles are found in almost every habitat except the sea and the polar regions.
Most beetle species complete their lives in a single year. Some, especially larger ones, live for more than a year, hatching in summer, a few months to a year or more as a larva and pupa, and then emerging to reproduce as an adult.
Termite queens have the longest lifespan of any beetles or insects in the world, with some queens living up to 50 years.
The heaviest beetle, indeed the heaviest insect stage, is the larva of the goliath beetle, (Goliathus goliatus), which can attain a mass of at least 115 g (4.1 oz) and a length of 11.5 cm (4.5 in).
The longest beetle is the Hercules beetle (Dynastes hercules), with a maximum overall length of at least 16.7 cm (6.6 in) including the very long pronotal horn.
The smallest recorded beetle and the smallest free-living insect, is the featherwing beetle (Scydosella musawasensis) which may measure as little as 0.325 mm (0.0128 in) in length.
Beetles are like all insects, they have a head, thorax, and abdomen, and six legs. Their bodies tend to be very solid and tough.
Adult beetles have modified wings: the first pair of wings is small and very hard, and acts as a protective covering for the second pair of wings. Many beetles can fly with their second pair of wings.
Beetles have chewing mouthparts and often have powerful jaws.
Beetles eat all kinds of food. Most are specialists in few kinds, but some, like ground beetles, eat lots of things. Most beetles eat plant parts, either leaves or seeds or fruit or wood. Many are predators on other small animals. Some eat fungus, and there are a bunch of species that eat dung. Sometimes the larvae eat different foods than the adults do.
Most beetles communicate with other beetles with chemicals. Males often locate females by their scent. Beetles usually can’t see very well. Some beetle make sounds, usually scraping their mouth parts together or rubbing their legs on their bodies. Some beetles that live in dead wood drum and make vibrations. Another way beetles find mates is seen in the fireflies which are bioluminescent, with abdominal light-producing organs.
The life cycle of a beetle is known as a complete metamorphosis, meaning it has four very different stages. Adult female beetles mate and lay eggs. The eggs hatch into a larval stage that is wingless. The larva feed and grow, and eventually change into a pupal stage. The pupa does not move or feed. Eventually the pupa transforms into an adult beetle.
Parental care is found in a few species of beetle, perhaps for protection against adverse conditions and predators.
Beetles, both adults and larvae, are the prey of many animal predators including mammals from bats to rodents, birds, lizards, amphibians, fish, dragonflies, robberflies, reduviid bugs, ants, other beetles, and spiders.
Beetles use a variety of anti-predator adaptations to defend themselves. These include camouflage and mimicry against predators that hunt by sight, toxicity, and defensive behaviour.
Camouflage is common and widespread among beetle families, especially those that feed on wood or vegetation.
Some longhorn beetles are effective Batesian mimics (form of mimicry where a harmless species has evolved to imitate the warning signals of a harmful species) of wasps.
Chemical defense is important in some species, usually being advertised by aposematic colors where bright or contrasting coloration warn off predators; many other beetles and other insects mimic these chemically protected species.
Most beetles are active at night, but some are active in daylight (especially if they have chemical defense).
Many beetle species undertake annual mass movements which are termed as migrations. These mass movements may also be opportunistic, in search of food, rather than seasonal.
About 90% of beetle species enter a period of adult diapause, a quiet phase with reduced metabolism to tide unfavourable environmental conditions.
Fireflies produce a chemical reaction inside their bodies that allows them to light up. This type of light production is called bioluminescence. Unlike a light bulb, which produces a lot of heat in addition to light, a firefly’s light is cold light, without a lot of energy being lost as heat.
The tiger beetle, relative to its size, is the fastest creatures on Earth. The fastest species of tiger beetle, Cicindela hudsoni, can run at a speed of 9 km/h (5.6 mph), or about 125 body lengths per second. The fastest human can do about five body lengths. To take the sprinting gold from the tiger beetle, a person would have to hit 770 kilometers (480 miles) per hour.
Hercules beetles can lift 850 times their own weight. That’s equivalent to a human lifting 10 elephants.
One study investigating the flight altitude of the ladybug species Coccinella septempunctata and Harmonia axyridis using radar showed that, whilst the majority in flight over a single location were at 150–195 m (490-640 ft) above ground level, some reached altitudes of over 1100 m (3600 ft).
Scarab beetles held religious and cultural symbolism in Old Egypt, Greece and some shamanistic Old World cultures.
Beetle collecting became extremely popular in the Victorian era.
Many beetles have beautiful and durable elytra that have been used as material in arts, with beetlewing the best example.
Sometimes, beetles are incorporated into ritual objects for their religious significance.
Whole beetles, either as-is or encased in clear plastic, are made into objects ranging from cheap souvenirs such as key chains to expensive fine-art jewellery.
Beetles are the most widely eaten insects, with about 350 species used as food, usually at the larval stage.
In Japan the practice of keeping horned rhinoceros beetles and stag beetles is particularly popular amongst young boys. Such is the popularity in Japan that vending machines dispensing live beetles were developed in 1999, each holding up to 100 stag beetles.
Fighting beetles are used for entertainment and gambling. This sport exploits the territorial behavior and mating competition of certain species of large beetles.