Beetle

This article covers the insect order of the beetles . Other meanings can be found under Beetle (disambiguation) .

Beetle
Wood dung beetle ( Anoplotrupes stercorosus )
Systematics
Trunk : Arthropod (arthropoda) Superclass : Six-footed (Hexapoda) Class : Insects (Insecta) Subclass : Flying insects (Pterygota) Superordinate : New winged wing (Neoptera) Order : Beetle
Scientific name
Coleoptera
Linnaeus , 1758
Submissions
Archostemata Myxophaga Adephaga Polyphaga For families see the beetle system

The beetles (Coleoptera) are more than 350,000 described species in 179  families , the world's largest order from the class of insects - still hundreds of new species are described each year. They are common on all continents except Antarctica ; in Central Europe there are around 8000 species. The oldest fossil beetle finds to date come from the Permian and are around 265 million years old.

The body structure of the beetle differs from that of other insects because the apparent three-part structure does not correspond to the head, chest and abdomen, but the second section consists only of the prothorax , of which only the pronotum is visible on the upper side of the body . The remaining two sections of the breast form a unit with the abdomen and are covered by the sclerotized first pair of wings, the cover wings .

With a length of around 170 millimeters, the giant longhorn beetle ( Titanus giganteus ) from Brazil is the largest species of beetle; The Goliath beetles , weighing around 100 grams, are among the heaviest insects of all. In Europe, the size of the beetle varies between about 0.5 and 75 millimeters, the largest Central European beetle is the stag beetle ( Lucanus cervus ).

etymology

The word beetle has Germanic roots. Already in the 9th century, the word is cheuur , in the 10th century chefuar , a century later, the expressions find cheuove , cheuer and keuir . However, they did not designate beetles, but locusts. The word kever is documented from the 13th century , word related to pine . Both words are derived from a root word meaning "chew, gnaw". Only in the following centuries did the meaning of the word kefer change from “grasshopper larva ” to “beetle”. The Germanic peoples also used the word webila for beetles . In the 11th century the word wibil appears , in the following century wibel , which lives on in English in the form weevil as a term for the weevil and in dialect names like Perdswievel for horse beetle. Distinctions such as scaernwifel and tordwifel for dung beetles were found early on , and different families of beetles were linguistically differentiated in the 15th century.

The scientific name Coleoptera comes from ancient Greek. With κολεός ( koleos ) the leather cover in which the sword was put was called, and with πτερόν ( pteron ) the wing. The beetle's leathery-looking wings, which partially envelop the rear wings, led to the name.

Characteristics of the beetle

The three-part division of the body is easy to see in the black gravedigger

The body shape of the adults is very diverse and varies from very long and slim to squat, short types. There are very flat to strongly spherical bodies. The body shape represents an adaptation to the way of life of the respective species. Beetles that live under loose bark are always flat; Aquatic species, especially fast swimmers, are streamlined; climbing beetles, whose escape behavior consists in dropping themselves in danger, are spherical. The structure of the body surfaces is also very different. The spectrum ranges from smooth and shiny to highly structured surfaces with wrinkles, pits, grooves and bumps. A decisive evolutionary factor for the development of the body shape is the function of camouflage from predators , especially in the case of bizarrely shaped species .

The body structure of the beetle follows the basic structure of the insect. The body consists of three sections: the head (caput), chest ( thorax ), and abdomen ( abdomen ). The visible structure of the beetles does not correspond to the head, chest and abdomen. The second visible portion consisting only of the first segment of the chest, the second and third segments form with the abdomen of a unit from the deck wings is covered (elytra). The elytra are the first, heavily sclerotized pair of wings that protect the second pair of wings. On the abdomen side, the rear parts of the chest protrude beyond the first abdomen segments, so that here too the second and third breast segments together with the abdomen form an optical unit. With a few exceptions, beetles have a severely sclerotized exoskeleton with involvement of chitin . Like all insects, they have six legs and two antennae, which are very differently shaped in the individual species . Beetles are insects with chewing mouthparts . Like all insects, they have a rope ladder nervous system that has been modified so that there are no longer any ganglia in the abdomen . The blood vessel system is open and has a tubular heart . The simple digestive tract with the Malpighian vessels and the tracheal system for breathing also correspond to the general plan of the insects. However, due to the diversity of beetles due to the long evolutionary period, there are deviations from this basic plan in almost all areas of the beetle's anatomy.

height

The body size of the beetle is limited by the fact that the air has to be transported through the tracheal system to the organs. The largest beetles are therefore relatively sluggish. The lower body size is only limited by the fact that the relatively complex body structure can still be achieved. The species of dwarf beetles (Ptiliidae) and point beetles (Clambidae) are among the smallest beetles and the smallest insects at all; there are species that are less than 0.5 millimeters long. Fire beetles (Pyrochroidae) and oil beetles (Meloidae) are families with very large species on average. The largest species worldwide, however, are the longhorn beetles (Cerambycidae) and rose beetles (Cetoniinae). Within these families, however, there are great differences in length; the smallest longhorn beetle is only about three millimeters long, with about 170 millimeters in length the giant longhorn beetle ( Titanus giganteus ) is the largest known species of beetle. The body size of representatives of a species can vary considerably, for example the body length of the musk billy goat varies between 13 and 34 millimeters. Since the adults can no longer grow, such differences in size are solely due to different favorable living conditions during the larval stages . There are sometimes, but rarely, significant differences in size between the sexes of the same species. There are noticeably larger males, for example, among the stag beetles , in which the males fight territorial fights. Usually, however, the female is the larger sex.

coloring

Polyteles coelestina from South America

The color of the beetles is just as diverse as their body shape. Most of the beetles are dark or colored in shades of brown; but there are numerous types with patterned, brightly shining or shiny metallic bodies. The color is caused by pigmentation or structural colors .

The color, which is usually metallic, is caused by physical phenomena such as interference or scattering . This often occurs with thin-layer structures such as hair (setae) or scales or with special layering of the layers of parallel chitin fibers. The color of the hair and scales often covers the basic color. Patterns can come about when the basic color emerges in hairless or unscaled areas. For this reason, older animals, in which the hair has disappeared, often look different than animals newly hatched from the pupa . At the same time, newly hatched beetles are usually not fully colored in the first few hours. In many species, males and females are colored differently ( sexual dichroism ).

In some species of beetle, a striking constancy of the drawing can be seen, in others, however, a strong variability. The ladybirds (Coccinellidae), for example, have species that produce hundreds of different patterns and colors. In the past, these animals were given their own aberration names , if they were not even treated as separate species, and thus placed in the status of systematic groupings. However, these assumptions are now scientifically outdated; most of these terms are no longer in use today. At the other extreme, for example, in the genus Trichodes from the family of the longhorn beetles or in the genus Clytus from the family of the longhorn beetles, the patterns in the different species are almost the same. The coloring of the animals is also often an important characteristic for their camouflage and defense (see Camouflage and Defense below).

head

The head is the center of the animal's nervous system . It contains the two most important concentrations of nerve cells, the upper and lower pharyngeal ganglion , which are collectively referred to as the brain. In addition, there are many sense organs in the head, although not all. The most important parts are compound eyes , antennae and mouthparts. The head capsule, which protects the brain, consists of an acron (head flap) and six segments that are fused together. The head can be shaped very differently depending on the species. There are round to angular and short to extremely elongated head shapes. In some species, the head can be extended forward by a large head shield. The head is divided into several areas:

designation	position
Forehead ( frons )	front area
Temple ( tense )	between the eye and the back of the head
Cheek ( Gena )	Side of the head in front of the eyes and the parting
Apex ( vertex )	Top of the head behind the eyes

Mouthparts

The powerful mouthparts of the mountain tiger beetle

The beetles have biting and chewing mouthparts . These represent the most original form of the mouthparts, in which the relationship to the head legs of the crustaceans is still recognizable. Nevertheless, they show a high degree of specialization in the respective diet. They consist of paired mandibles (upper jaw) and paired maxillae (lower jaw) as well as an unpaired labium (lower lip). The labium consists of an unpaired basal piece that functions as the lower lip. Then the unpaired tongue ( glossa ) follows up with the two secondary tongues ( paraglossae ). The mouthparts are closed at the top by the labrum (upper lip), an unpaired plate. The mandibles are the most important tools for obtaining food. They are used by herbivores to cut off parts of plants and to chop them up; The predators can grab their prey with their pointed and sharp mandibles, hold it tight and cut it into edible portions. A few species cannot use their mandibles for food. In the males of the stag beetles, for example, they are so enlarged that they cannot be used as eating tools. Instead, they are converted into weapons with which the males rivaling females fight and impress . Both on the maxilla and on the lower lip there are buttons, so-called palpi , on which the sense of taste sits.

sensor

The Moschusbock has as many longhorn beetle very long antennae

The beetle's antennae arise on the head. The position of their point of deflection (between or in front of the eyes, inside or behind the root of the upper jaw and the like) often plays a role in the determination keys. As with all insects, the antennae are designed as flagella antennas that have only one basal or shaft segment with muscles, the scapus . The following turning link, the pedicellus , is movable together with the flagellum compared to the scapus. Depending on the family, the antennae have a total of five to twelve members, but mostly they have ten or eleven members. They are shaped very differently. In some families, the males have differently shaped antennae (usually larger and longer) than the females. A distinction is made between thread-shaped (e.g. ground beetles), culled (weevils) or fanned (cockchafer) and combed (stag beetles) antennae as basic types. Regardless of this, a feeler is called "kneeling" when it is angled. But there are numerous gradations between these basic forms. The turning point and the structure of the antennae are often characteristic of a family or some other systematic unit. Organs with which the animals can smell sit on the antennae, but they are also tactile organs with which they orientate themselves. In some families, they are also used to hold the sex partner in place during the mating position.

eyes

The eyes are designed as compound eyes . They are made up of individual eyes ( ommatidia ). In addition to the basic type of apposition eye , the simplest complex eye, in which each individual eye is separate and optically isolated from its neighbors, there are also so-called superposition eyes , especially in crepuscular and nocturnal beetles . In these, the individual eyes are not optically isolated, but the light rays can also reach neighboring ommatidia and stimulate the visual pigments of the rhabdome there to transmit the information about the light stimulation to the optic nerve. This enables vision even with lower light intensity and increases the perceived brightness many times over, but at the expense of visual acuity. At higher light intensity, the pigment cells can shift, which functionally creates an apposition eye again. The beetle's eyes are not always round. They are mostly located in a kidney shape around the base of the antennae. In extreme cases, such as with many longhorn beetles, these "halves of the kidney" are separated.

A special case is the tumbler beetles (Gyrinidae) that live in water. In these beetles, the halves of the eyes are moved apart, the upper halves form a pair of eyes that are above the water level, the lower halves of the eyes form a pair of eyes below the water level. They can see above and below water at the same time, whereby the respective pairs of eyes are adapted to the different light intensities, wavelengths and refractive indices of air and water. A few families of beetles , such as the bacon beetles (Dermestidae), only have simple pinpoint eyes , like the beetle larvae, while other species that live in caves have completely regressed their eyes. They include several representatives of the ground beetles (Carabidae), which are endemic to only one cave, or, for example, the Segeberger cave beetle from the sponge- ball beetle family .

Chest (thorax)

The beetle's thorax consists of three parts: prothorax , mesothorax, and metathorax . From above you can only see the first section, the prothorax. This is covered by the pronotum (scutum). The other two thoracic segments are below the deck wings (elytra) is hidden, with the exception of a small part of the Mesothorax. This scutellum is, if at all, recognizable between the wings at the base as a small triangle. The three thoracic segments are visible from below, but not easily recognizable as such. They consist of several sclerotized chitin plates, which can be shifted against each other, so that plates belonging to the front breast come to lie between those of the middle breast. In particular, the plates of the rear chest protrude at least over the base of the abdomen, so that the delimitation from the abdomen is not easily recognizable and the middle and rear chest appear to belong to the abdomen. A pair of legs arises from each of the three breast segments, and the two pairs of wings also arise from the two rear segments.

legs

The legs have the same basic structure as the other insects. Each leg is divided into several sections - hip ( coxa ), thigh ring ( trochanter ), thigh ( femur ) and splint ( tibia ) - and has two to five-limbed feet ( tarsi ) at the end , with the last tarsal segment having claws. The number of tarsus links is used for the basic classification of the beetle families. For example, 5–5–4 means that the hind legs have four tarsi and the remaining legs have five. The tarsi and the other leg segments can be of very different lengths and shapes. Individual segments can be built so small that they are hidden in the preceding limb, like the fourth tarsal limb of longhorn beetles (Cerambycidae). Often the legs are also widened. This is so much the case with the green horned beetle ( Oedemera nobils ) that the thighs appear almost spherical. The legs are specialized depending on the type of beetle and use and can be designed as walking legs, jumping legs, swimming legs or digging legs. The Australian tiger beetle Cicindela hudsoni achieves a top performance in the class of insects with a speed of up to 2.5  meters per second . Jellyfish beetles ( Dytiscus marginalis ) can swim up to 0.5 meters per second with their powerful swimming legs.

wing

Cockchafer with folded front wings and an unfolded pair of rear wings

The defining difference between beetles and other insects is their wing structure. In beetles, the first pair of wings differs significantly from the second. The fore wings ( elytra ) arising from the middle thoracic segment are heavily sclerotized and essentially only serve to cover and protect the artfully folded rear wings and the abdomen. With a few exceptions, they are folded forward diagonally during flight so that the rear, flightable pair of wings can be unfolded. In the closed state, the cover wings form the wing cover seam on their inner edges . However, they often diverge towards the rear. In most beetles, they are firm, and in some, such as the weevils , they are even very hard. The soft beetles , on the other hand, have very soft wings. The second pair of wings ( Alae ) arises on the rear thorax segment and, like most insects capable of flying, is designed as skin wings. The hind wings are reinforced on the stabilizing wing veins and otherwise membranous. They only unfold shortly before the start and are usually much larger than the Elytres. After the flight, they are usually folded again with the help of the hind legs and pushed under the wing.

The construction of the wings varies greatly. The cover wings can be of different lengths and either completely or predominantly cover the abdomen, or they leave the abdomen completely uncovered , as is the case with short-winged birds. The two wings can also have grown together, as is the case with many ground beetles (Carabidae). The hind wings of these species are then mostly stunted or missing completely. The surface of the upper wing is sometimes very different. There are smooth, scaly, hairy, and textured wings.

Abdomen (abdomen)

Short-winged , abdomen threateningly raised; The shortened wings are clearly visible

The abdomen consists of several, usually eight or nine visible segments. The rearmost abdominal segments are hidden in the body. The visible segments consist of two half-shell-shaped parts, the tergite on the back and the sternite on the belly. The two parts are connected laterally, parallel to the longitudinal axis of the body, by the pleurite . The individual segments are connected to one another by segment skins. As a result, the abdomen, in contrast to the rigid front body sections, is mobile. However, compared to most other insects, mobility is rather limited. In some species, such as the genus Dytiscus from the family of the swimming beetles (Dytiscidae), the abdomen is immobile. The short-winged species, on the other hand, can move the abdomen particularly well. When threatening, they lift the end of the abdomen steeply upwards and thus appear much larger. The sex organs are contained in the last abdominal segments .

internal structure

The two main tasks of the blood in vertebrates, the transport of respiratory gases and the substances important in food metabolism, are performed by two different systems in beetles, as in insects in general. The body fluid that takes on the task of transporting nutrients is called hemolymph . It does not flow in veins , but in spaces and body cavities and washes around the beetles' organs. The hemolymph does not contain hemoglobin and can be colorless or yellow, but sometimes also red or green. The only blood vessels are a short aorta and a tubular heart that sits in the upper part of the abdomen. The heart has eight pair of lateral openings ( ostia ), corresponding to the number of abdominal rings through which the blood is sucked into the heart. The heart passes into the aorta, and the hemolymph is transported from the heart through the aorta to the head. The transport takes place with a system of sail flaps. However, no oxygen or carbon dioxide is transported, the gas exchange takes place via tracheas , which with their highly branched tube system supply all organs with oxygen. This is pumped into the body through lateral openings (spiracles), which can be clearly seen, for example, in the field cockchafer ( Melolontha melolontha ), when its abdomen performs significant pumping movements before take-off. The maximum transport path is limited in this respiratory system, which is also the reason why beetles and insects are generally limited in their growth in size. The heart beats relatively slowly, for example in the stag beetle ( Lucanus cervus ) about 16 times a minute.

The nervous system is found on the beetle's belly, which is why it is also called the belly marrow. It differs to a greater or lesser extent from the structure typical of insects and is of unusual diversity within the order. The total of eight abdominal ganglia are sometimes shifted into the thoracic region. Depending on the species (as in the basic plan of the pterygota), all eight abdominal ganglia can remain separate (in Lycidae) or all, including the three thoracic ganglia, merge into a compact mass (in some weevils). The number of separate ganglia varies, for example, from two to ten for ground beetles, from one to five for weevils, and from two to seven for leaf beetles. The brain consists of a sub- pharyngeal ganglion , an upper pharyngeal ganglion and another ganglion. Overall, it is significantly smaller than the thoracic ganglion and lies below or above the esophagus . The brain and thoracic ganglion are independent of each other, so the body can remain largely functional for some time after the loss of the brain.

The digestive system consists of an intestinal tract, which can be divided differently in different families. In carnivores it is relatively short, in herbivores it can reach ten times the body length. From the throat ( pharynx ), the food reaches the stomach via the esophagus. The adjoining midgut has a long-shaggy inner surface in the front section and a short-shaggy inner surface in the rear section. The rectum is divided into the small intestine ( ileus ) and large intestine ( rectum ). In it, nutrients are absorbed into the blood. There, as well as in the two tubular kidneys ( Malpighian vessels ), metabolic products are absorbed from the organs and excreted through the anus . Some beetles, such as the bombardier beetles (Brachininae), have glands in the large intestine, the secretion of which can be used for defense purposes ( defense secretion ).

In the male, the sexual organs consist of paired testes, different glands, which can be built very differently in the respective families, and the draining ducts. Appendix glands and seminal vesicles also vary. A common execution passage leads to the copulation tools. The females have ovaries, appendix glands, and purgative vessels in various shapes. A seed pouch can be tied to the vagina, in which the male semen is kept until the eggs are laid. Mating and insemination can be several months apart. Glues are occasionally used to lay eggs, for the production of which glands exist. The external genital organs are heavily sclerotized, especially in males. Their complex and species-specific shape, which is highly specialized according to the key-lock principle, enables many beetles, which cannot be distinguished externally, to be assigned to a well-defined species through genital examinations .

Way of life and behavior

nutrition

The spotted small buck feed on nectar and pollen

Beetles inhabit most of the world's habitats and there is virtually no organic food source that is not tapped by certain species of beetles. Larvae often feed very differently than adult beetles. The food spectrum of individual species also varies greatly. The herbivorous beetles range from polyphagous species that feed on a variety of different food sources to monophagous species that only eat a certain type of plant. There are numerous specializations. There are wood-eaters ( xylophages ), rot-eaters who feed on decaying plant parts ( saprophages ), and those who specialize in dead wood (saproxylophages). Most herbivores feed on the leaves, flowers, seeds, roots or stems of the plants.

Many ground beetles, such as the gold ground beetle , feed predatory

The predatory families, such as the ground beetles (Carabidae), have a wide range of food. In addition to insects , other arthropods , worms , snails and caterpillars , these beetles also eat vertebrates such as tadpoles or small fish if they are available. Only a few beetles chop up their prey before eating. Most inject digestive juices in order to ingest the liquefied food ( extraintestinal digestion ). Some predators also eat plant foods such as seeds or pollen .

Bacon beetles, like the woolly flower beetle larva , feed on dry organic matter

In addition to these two groups of types of nutrition, there are two particularly ecologically important ones, namely that of coprophages and that of necrophages . The former feed on feces , such as the dung beetles (Geotrupidae), the latter eat carrions , such as the carrion beetles (Silphidae). These species feed excretions or carcasses back into the food cycle by breaking them down. There are also fungus eaters ( mycophages ), such as the sponge beetles (Mycetophagidae), but also those that feed on leather , feathers , tendons, hair and dry skin, such as the bacon beetles (Dermestidae). Also inorganic substances, such as minerals are added directly to the part.

water

The common rodent beetle is not dependent on ingestion of water

In addition to nutrients, beetles, like all living things, depend on water. Some beetles that live underwater can fly very well in order to colonize new habitats if their habitat dries up. But they also do this, regardless of the endangerment of their waters, in order to develop new habitats. In addition to the beetles that live in water, such as swimming beetles (Dytiscidae), there are species that require high humidity and are therefore mostly found around bodies of water ( hygrophiles ). Still other species depend on moisture, but live in dry and hot places. Species that live in desert areas in particular , such as some black beetles (Tenebrionidae), are adapted to extreme drought. They are nocturnal and omnivorous because they cannot be picky when there is a lack of food. They can also take the water to cover their moisture requirements from their food as well as collect it by collecting condensation on their feet, which they point high up.

Some beetle larvae can even live without direct water intake. Species that live in very dry wood, such as the common rodent beetle ( Anobium punctatum ), digest the wood they eat with the help of bacteria. They store the energy gained in the form of fat. From this they can then chemically split off water.

breathing

Jellyfish beetle ( Dytiscus marginalis )

All beetles breathe through trachea and thus take in oxygen. This creates an additional problem for beetles living in the water that beetles do not have on land. You need to get oxygen to breathe because you can't get it directly from the water. There are very few exceptions, such as the larvae of the tumbler beetles (Gyrinidae), which take up oxygen directly from the water with the help of special organs, the tracheal gills . Tracheal gills are never found in adults.

The adults of the aquatic beetle species and the larvae of most families have developed very different ways of taking up oxygen. Most species come to the surface of the water and can take an air bubble with them on their dives. Some store the air between the wings and the abdomen, such as the yellow beetle ( Dytiscus marginalis ). Others , such as water beetles (Hydrophilidae), pump air through a channel formed by specially shaped feelers on the underside of the body , whereby the air is held there between hairs. There is also the possibility that they carry their air reserve with them as a bladder at the end of their abdomen, although this is only possible with small beetles, such as those of the genus Hyphydrus from the family of swimming beetles (Dytiscidae). The prerequisite for the transport of the air bubble is that the body cannot be wetted, which is ensured either by fine hair or by a layer of fat. The hook beetles ( Elmidae and Dryopidae ) are plastron breathers , so they do not have to come to the surface to breathe.

Most swimming beetles have, due to their breathing technique, a partly heavily modified and adapted body structure. The problem arises from the oxygen transport that the air that is carried along generates a high level of buoyancy and the beetles have to use a lot of energy to swim. This is why the large beetles in particular like to live in heavily overgrown waters and often cling to aquatic plants. Some species of leaf beetles (Chrysomelidae) that live underwater , such as those of the genus Macroples , do not have to fight against buoyancy. They get their oxygen directly from bubbles given off by aquatic plants. Even their larvae do not need to rise to the surface to breathe. The eggs are laid in stems of aquatic plants. The larvae that hatch from it either live directly in the plant and take oxygen from its conduction pathways, or they live in water and hook the end of the abdomen into these pathways from the outside. The dolls of the genus Donacia do the same . However, most of the beetles that live in water pupate on land.

Flight behavior and hikes

Tiger beetles like the dune tiger beetle are some of the best short-range flyers

According to the basic plan of the insects, the beetles have two pairs of wings , of which only the rear pair, the alae , is suitable for flying. The anterior is sclerotized and forms the protective elytra. Most beetles can fly more or less well, although species such as the tiger beetle (Cicindelinae) are very agile, can fly excellently and reach a maximum speed of up to 8 m / s. The situation is similar with some species of swimming or water beetles , such as the large piston water beetle ( Hydrophilus piceus ). These can fly over long distances in order to colonize new bodies of water, but appear very clumsy and not very agile at short distances. The ladybirds are also good fliers, reaching around 75 to 91 wing beats per second. The hind wings are not developed in all beetles. Most large beetles of the genus Carabus , for example, lack well-developed hind wings, and their cover wings are fused together at the wing cover seam .

When taking off, the upper wings, which have no function during the flight, are first unfolded and the membranous hind wings, which were previously folded up against the abdomen, are unfolded. The only exception are the rose beetles (Cetoniinae), in which the elytra remain closed when flying and the wings can be folded out and in via a recess on the side of the elytra. After the flight, the hind wings are folded again, usually with the help of the hind legs, and pushed under the wing. This process can take several seconds.

Most ground beetles, like the blue-violet forest ground beetle ( Carabus problematicus ), cannot fly

In addition to the short-haul flight, which is usually undertaken to find food or a partner, there are also numerous beetles that can travel very long distances. They often use the wind to help or are so dependent on it that they can only make minor course corrections. Beetles undertake such flights either to find suitable winter spots, as some ladybugs do, for example, or they fly because food is scarce in the previously inhabited area, or to expand into new habitats. In the first two cases it happens that the animals gather in huge swarms. Flocks of ladybirds from millions of animals have already been observed. They are based on the one hand optically and on the other hand also on climatic factors in order to achieve their goal. A classic example of a species that is often on the lookout for new habitats is the yellow beetle ( Dytiscus marginalis ). This species not only leaves its wetlands when water is scarce, but also under good conditions. You fly at night and orientate yourself optically. Moonlight reflected through glass, such as in greenhouses, can deceive the animals and induce them to land in what appears to be wet.

Special properties

Lily Chicken ( Lilioceris lilii )

Some species of beetle can make noises by rubbing parts of their bodies together. In addition to numerous longhorn beetles (Cerambycidae), the various chickens of the leaf beetles (Chrysomelidae), such as the lily chicken ( Lilioceris lilii ), can generate chirping noises by rubbing the rear edge of the elytra with the abdomen. Dung beetles of the genus Geotrupes make noise by rubbing their abdomen against the wings . There are, however, numerous other ways of generating noises, such as friction between the crown of the head and the pronotum, between the throat and the prothorax , between the prothorax and the mesothorax, and between the legs and the abdomen or the wings. In addition to the noise generated by rubbing against each other, which is primarily used to deter predators, pied rodent beetles ( Xestobium rufovillosum ) can locate their sexual partners in duct systems in the wood by means of certain attractant calls. To do this, the beetles hit the wood very quickly with their head and pronotum. Some species of beetles from two subfamilies (tiger beetles and giant beetles) have developed eardrum-like tympanic organs to hear the ultrasonic location sounds of bats they hunt.

Great firefly female ( Lampyris noctiluca )

Some beetles have the ability to generate light ( bioluminescence ), including the firefly (Lampyridae). Each species generates specific light signals, whereby mostly the males fly around brightly or the flightless females draw attention to themselves brightly. For this purpose, light organs are formed on the underside of the animals' abdomen, which originally developed from fatty bodies. They consist of a layer of bright, light-generating cells and a dark, further inner layer that serves as a reflector. The glow is created by the conversion of luciferin with ATP and oxygen by the enzyme luciferase . The energy released is emitted with an efficiency of up to 95 percent in the form of light and only the small remaining part as heat. Even the larvae or even the eggs of some species can shine in this way.

Reproduction and development

Asiatic longhorn beetle pupa

The beetles are counted among the holometabolic insects because they completely change during their development. In metamorphosis , the larva that hatched from the egg transforms after pupation into the imago, the fully grown beetle, which is very different in appearance and anatomical structure than the larva. The larvae go through different larval stages in their growth in which they molt as they increase in body mass. But they only change in size, not in shape. When they are fully grown, they pupate in a free pupa ( pupa libera ) in which all extremities, such as antennae, legs or wings, protrude and can also be recognized as such on the pupa. Very few species of beetles, such as the ladybird , pupate in a covered pupa ( pupa obtecta ). In the pupal stage, all organs and the entire body of the larva are converted into beetles. The doll is usually practically immobile, only some can move a little. After the pupal rest, the finished beetle can hatch and the cycle of beetle life can begin again.

The number of generations per year is very different. In Europe, most beetle species need a year to complete their entire life cycle. There are, however, both species that produce several generations in one year, as well as those in which a generation takes several years to develop.

Choice of partner, courtship behavior and fights

The male stag beetle has greatly enlarged mandibles with which rival fights are fought

As with many other insects, the sense of smell is not only very important, but also very well developed, depending on the species. This is noticeable in the males of some species because of their particularly large and combed antennae for finding the pheromones emitted by the females . Still, there are numerous ways that finding a partner is left to chance. That is why such species seek places where conspecifics are likely to be encountered, such as yellow flowers in certain jewel beetles (Buprestidae).

In general, beetles cannot see well, and spotting partners does not work well even at close range. Because of this, there are often mismatches in the species that do not look for smell, as other beetles, also sitting on yellow flowers, are mistaken for their own species. Males usually do not fight directly for females, but for courtship grounds. These are either suitable egg-laying places , such as pine stumps in the carpenter's buck ( Acanthocinus aedilis ), or places where the beetles often meet, such as on yellow flowers, as described above. The best-known example of rival fights in Europe is provided by the stag beetle ( Lucanus cervus ): the males are attracted by the pheromones of the females. If two males meet a female at the same time, they try to knock the opponent over with their greatly enlarged mandibles , which are used exclusively for combat, or to knock them off the branch. After the fight, the winner can mate with the female.

pairing

Spotted narrow-bucks when mating

The mating (copula) of the beetles takes different lengths of time: from a few seconds, as with Hoplia coerulea , to several hours (up to 18), as with ladybirds (Coccinellidae). The pairs are either very loosely connected and easily separate in the event of a disturbance, or they cling very tightly to each other and cannot be separated without injuring the animals. During sexual intercourse, the male uses the penis to push apart the sternites on the female's abdomen, under which the sexual opening is located. After that, the male enters and the semen is transferred through spermatophores . After mating, the male releases itself from the female either with its hind legs or by rolling sideways. One mating is sufficient to fertilize the female permanently, but in some species, such as many ladybirds, up to 20 further matings are carried out ( promiscuity ). Because these beetles then have many different sexual partners, the risk of transmitting sexually transmitted diseases that lead to infertility is high. In most species, the sperm are kept by the female in a spermatheca ( Receptaculum seminis ). The eggs do not have to be fertilized with the sperm right away. As with some other insects, this can be kept in the seed container for a long time before it is used. Once the eggs are fertilized, the female lays them. In the black ball ladybird ( Stethorus punctillum ), for example, the spermatheca is missing, which is why new partners are necessary for further fertilization over the entire fertile period.

Only one type of beetle, Micromalthus debilis from the Micromalthidae family , can reproduce asexually ( pedagogically ).

Egg, egg laying and brood care

A red-necked silphe is looking for a suitable place to lay eggs on a dead fish

Lilies eggs laid on the appropriate food plant

The beetle's eggs are rather small compared to the size of the adult animals. They are very difficult to spot individually; However, since they are usually placed in groups or in mirrors next to each other and some are strikingly colored, such clutches are more likely to attract attention. The shape of the eggs is very varied, there are round, oval, cylinder, sausage, spindle and cone-shaped eggs. They are usually white or light in color, but there are also numerous other colors; the eggs of most ladybird species (Coccinellidae) are colored yellow to orange. Depending on the species, a few to well over a thousand eggs are laid, these being laid individually or in clutches of different sizes.

The care of the beetles varies greatly among the different families of beetles. Most of the hatching care ends with the eggs being placed where the hatching larvae find food. They are either placed on the appropriate forage plants or placed close to the larval food, such as ladybug eggs on aphid colonies . In the simplest case, beetles and larvae eat the same diet anyway and the females do not have to look for suitable sources of food for their larvae. In the next more difficult level, in which the two stages feed each other differently, the females have to specifically choose wood from certain fodder trees, for example, although they may feed themselves on pollen. Additionally, there is the possibility that the females hide their eggs, edit the space or the eggs directly laying drills prick in plants. For example, the bark can be gnawed so that the plant then forms a bile that the larva feeds on, as in the case of the small poplar buck ( Saperda populnea ). Other beetles, such as many leaf rollers (Attelabidae), first cut leaves in order to then fold them so that their larvae can develop well protected in these withered leaf coils. Numerous species of closely related weevils (Curculionidae) proceed in a similar manner, piercing their eggs into parts of plants and fruits, in which their larvae then develop. There are also beetles that let other species take care of their brood: the cuckoo weevil ( Lasiorhynchites sericeus ) waits until an oak leaf roller ( Attelabus nitens ) has finished rolling its leaf and then pierces its egg into the leaf roll. Water beetles (Hydrophilidae) build small boats for their eggs, which float on the surface of the water. They even have a “chimney” extended upwards so that the oxygen supply is guaranteed even if the capsule is submerged.

Common dung beetle ( Geotrupes stercorarius )

Egg-laying becomes more complex when structures are created for it. Numerous beetles, especially dung beetles (Geotrupidae), either build a duct system of varying complexity directly under their food ( dung pile) in the soil, into which they then bring food, with an egg being placed next to the food in each chamber. Others, such as the sacred pill turner ( Scarabaeus sacer ), roll a ball of feces meters wide before burying it in a suitable place. There are also beetles that bring plant matter or algae into their breeding chambers. The grave diggers ( Nicrophorus spec. ) Are particularly spectacular . They bury whole carcasses of small birds or mice. In addition, the female vomits intestinal secretions on the carcass so that it begins to dissolve, and she even feeds her larvae immediately after hatching. The female wakes up in the brood chamber until pupation , defends the brood against enemies and repairs damage. This behavior is no longer called brood care, but brood care , since the beetles actively look after their larvae even after they have laid eggs.

The simplest form of brood care is to move the eggs around. The females of the species Helochares lividus , a representative of the water beetle, carry their eggs in a woven bag under their abdomen until the larvae hatch.Other beetles, such as the lined wood beetle ( Xyloterus lineatus ), do not tend their brood, but indirectly their food. They drill a system of ducts in wood in which they lay the eggs and grow an ambrosia mushroom in them , the spores of which they carry around in their stomach. The larvae feed on these fungi. The parents ensure the right humidity and also sort out bacterial foci and other molds. What is remarkable is the amount of care that the sugar beetles (Passalidae) do. These beetles live to form colonies and jointly take care of their brood . In addition to feeding, they also help their larvae with the construction of their pupal covers. The myrmecophilic beetle species, whose larvae grow up in ant burrows, are also interesting . Among them there are those who can survive only by a built by the females Kotpanzer, which protects them from the ants, others, such as the Large tufts beetle ( Lomechusa strumosa ) may be prepared from tufts ( trichomes ), a special secretion ( exudate ) secrete that the ants eat. This secretion is not food, but something like a luxury item . In return, the larvae are fed by the ants, but they also eat ants' brood.

Characteristics and way of life of the larva

Larva of the shotgun

Most species of beetles spend most of their lives in the larval stage. The larvae often need several years to develop, but the adults only live briefly and die soon after mating and laying eggs. The larval stage is the only one in which the beetle grows, which is why the conditions found by the larvae determine the subsequent size of the adult beetles.

The larvae differ considerably in construction and way of life from the adult animals. Just as the adults do, the larvae live in a wide variety of habitats and have a correspondingly diverse appearance and behavior, which can be understood as an adaptation to the way of life. Most larvae have an elongated and slender body and are brightly colored. They have little articulated antennae and only simple point eyes (ocelli). They either have three pairs of legs or stunted legs or no legs at all. Your body is bare to hairy. The nervous system of the larvae is, unlike that of the adults, a typical rope ladder nervous system.

The way of life of the larvae is often similar to that of adult animals, for example in the predatory ground beetles (Carabidae) the larvae are also predatory and accordingly have well-developed legs and eyes. In herbivores such as leaf beetles (Chrysomelidae), the larvae also live vegetarian on leaves and are similar in shape to caterpillars . But there are also beetles in which the larvae are voracious predators, while the adults are harmless herbivores, for example the water beetles (Hydrophilidae): The larvae of these beetles live under water and feed predatory, the adult beetles are only partially aquatic animals. Larvae that feed on wood and always live in their feeding passages, such as those of the longhorn beetles (Cerambycidae) or the jewel beetles (Buprestidae), have receded their legs because their body bulges are better suited for locomotion in the passages. The sclerotization of the body is reduced because they are relatively protected in their feeding ducts, only the jaws are heavily sclerotized so that they can chop hard wood. Some beetles, such as oil beetles (Meloidae) or shipyard beetles (Lymexylidae), have different types of larvae that differ in appearance and way of life ( hypermetamorphosis ).

The duration of the larval development depends strongly on the way of life. Species that are severely threatened by enemies and those that depend on food that is only available for a short time, such as carrion, must develop quickly. Larvae that live protected in wood and have sufficient food available, for example, can develop very slowly. The duration also depends on the quality of the feed and the environmental conditions, such as temperatures. The house buck ( Hylotrupes bajulus ), for example, needs up to 15 years for its development with very old and nutrient-poor wood.

Since the outer skin of the larvae does not grow, they have to shed their skin from time to time in order to grow. The old skin then bursts open and the larva can crawl out with its new, stretchable and larger skin that has already formed under the old one.

Larvae of the main beetle families

The picture on the right shows the larvae of the most important beetle families.

• Top row: (4)  ruff beetles , (1)  tiger beetles , (6)  gloss beetles
• 2nd row: (5)  carrion beetles , (2)  ground beetles , (7)  bacon beetles
• 3rd row: (8)  scarab beetle , the grub , (3)  swimming beetle , (9)  jewel beetle
• 4th row: (10)  click beetles , ( wireworm ), (11)  soft beetles , (12)  colored beetles
• 5th row: (14)  black beetle ( mealworm ), (13)  thief beetle , (15)  weevil , (16)  drill beetle
• Last row: (17)  longhorn beetles , (18)  leaf beetles , (20)  shield beetles , (21)  ladybirds , (19) also leaf beetles

Doll and hatch

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Hatch of the beewolf

In order to carry out the metamorphosis from larva to imago, the animals pupate. Pupation takes place either in the larval habitat, for example in longhorn beetles in the wood, or the larvae look for suitable places for pupation outside of their usual environment. Almost all beetle larvae living in the water leave the water, for example, to pupate on land. At a suitable location, a doll's cover is made from pieces of sand, earth, wood or plants. Within this shell, the pupa is transformed through the complete dissolution ( histolysis ) of its body interior and the subsequent rebuilding of the finished beetle. Most of the beetles are free pupae (pupa libera), which means that the body appendages such as antennae, leg and wing sheaths are recognizable and not stuck to the body, as is the case with the pupa obtecta. When the pupa hatches, the shell bursts open and the adult beetle emerges. After hatching, the beetles are still soft and light in color. It takes some time for the shell to harden and the animals to get their final color.

wintering

Many ladybugs, such as the sixteen-spotted ladybug , overwinter in large groups

The beetles, which have to live with the seasons, usually overwinter in the pupal stage and only hatch in spring. But there are also species that overwinter as adults. Numerous ladybirds, for example, are one of these and usually form aggregations that can often include millions of individuals. Water beetles have a type of antifreeze in their body fluid that is similar to ethylene glycol . This means that some species can survive frozen in the ice for up to nine months. Before they go to sleep, they accumulate fat, lipids and glycogen in their bodies to feed on while they rest.

Natural enemies

The enemies of the beetles can be divided into three groups. Viruses, bacteria, protozoa and fungi are known to cause diseases in beetles. The clinical pictures can be very different and little researched. Some of the pathogens are already being used for biological control of certain species. Second, all stages of development, i.e. egg, larva, pupa and imago, are attacked by numerous parasites or parasitoids . These belong mainly to the hymenoptera and, among these, mainly to the parasitic wasps . Caterpillar flies and mites are also common .

The third group includes predators, to which birds in particular belong. Almost all European bird species eat beetles at least occasionally. Insect-eating mammals such as moles , hedgehogs , shrews and, for beetles flying at night, also bats are to be mentioned. But many reptiles, amphibians and fish also eat adult beetles or larvae. Among the arthropods, the spiders should be mentioned as predators, as well as numerous predatory insects, not least many species of beetles themselves.

Camouflage and defense

Common ram ( Clytus arietis )

Well camouflaged tortoise beetle

Since beetles and especially their larvae are very low in the food chain , they had to invent methods in the course of their development to protect themselves from attacks by their predators. The more effective these methods are and the more offspring survive and in turn produce offspring, the lower the need for many offspring. Species that are avoided by predators or are difficult to discover therefore usually lay fewer eggs than those that can rely solely on their large numbers.

The simplest protection starts with the passive skills. This includes the coloring. Many leaf beetles (Chrysomelidae), for example, are green in color and are difficult to spot in their habitat, the foliage. Other beetles are very conspicuously colored and warn potential enemies of their toxicity with warning colors , such as ladybirds (Coccinellidae), which contain poisonous alkaloids , or they imitate poisonous or dangerous animals ( mimicry ), such as the billy wasps ( Plagionotus ) from the Longhorn beetles (Cerambycidae) family , although they are actually harmless. In addition to these simple passive methods, some species of beetles have also developed methods that guarantee greater protection. Some species, particularly their larvae protect themselves by covering their bodies with mud, dust and soil, such as the larvae of the tortoise beetle (Cassidinae), which goes so far that, for example, the larvae of the great tufts beetle ( Lomechusa strumosa ) who live in ant burrows, spend their entire development in a fecal armor, into which they can withdraw and from which otherwise only the head looks out. The active defense begins with death ( thanatose ), whereby a drop of hemolymph, which is toxic or smells unpleasant, is often excreted at the same time as the reflex bleeding . In this way, ladybirds, for example, can escape those enemies who are put off by supposedly rotting beetles. Click beetles (Elateridae) have a quick mechanism that enables them to snap out like a taut spring, which they can use to scare attackers. This mechanism also helps you to get back on your feet if you land on your back. Another method of defense is to inject digestive juices in addition to pinching and biting with the mandibles . Many ground beetles (Carabidae) use this method. In addition, they can also secrete malodorous substances.

The bombardier beetles (Brachininae) developed the most aggressive method of self-defense . You can push irritating and foul-smelling gases with enormous pressure from two tubes in your abdomen in the face of attackers. The beetles make the explosive by mixing two very reactive chemicals ( hydroquinone and hydrogen peroxide ). When attacked, they add the enzymes catalase and peroxidase to the mixture in an explosion chamber in order to accelerate the reaction. These catalysts convert the hydroquinone into quinone and the hydrogen peroxide into water and oxygen. This leads to a violent chemical reaction, in which both heat and high pressure are generated and a caustic gas mixture, around 100 ° C, shoots at the attacker with a bang from the rear of the insect.

Distribution and habitats

The fact that beetles occur in an enormous variety is already an indication that they have adapted to practically all habitats on earth. Apart from the perpetual ice of Antarctica , there is no area that they have not colonized and, with the exception of the oceans, no habitat that is not inhabited by beetles. All freshwater is inhabited by a variety of beetle species, but apart from salt-loving ( halobiont ) beetle species that inhabit brackish water , salty areas inland and the coasts of the sea, there are no beetles in pure salt water . Ground beetles are characterized according to their location preference .

Some beetles also inhabit the nests and structures of other animals. In addition to the species that eat remains in nests, such as some species of the bacon beetles (Dermestidae), there are beetles that have specially adapted to life with other animals. These include in particular the myrmecophilic species such as the genus Clytra from the leaf beetle family (Chrysomelidae), whose larvae live in ant nests. A few species are ectoparasitic, for example Leptinus testaceus on mice and the "beaver flea" Platypsyllus castoris on beavers. The larvae of some species are parasitoids. In the genus Aleochara (Staphylinidae) they develop for example pupae of Diptera of the genus Cyclorrapha as Ektoparasitoide (within the Puparienhülle but outside the Dipterenlarve).

Systematics

External system

Within the subclass of flying insects (Pterygota), the beetles are part of the parentage of the new winged insects (Neoptera). Of these split over the Eumetabola the holometabolous insects from. The holometabolic insects, also called Endopterygota, are divided into the group of reticulated winged (Neuropterida) and Coleopteroida on the one hand and the hymenoptera (Hymenoptera) and Mecopteroida on the other. The Coleopteroida are further divided into beetles (Coleoptera) and fan-winged birds (Strepsiptera), which are therefore most closely related to the beetles. Their closest relatives are the camel neck flies (Raphidioptera), large-winged (Megaloptera) and reticulated winged (Neuroptera) in the reticulated winged group. The position of the Strepsiptera in the system is very controversial; there are both opponents and supporters among the taxonomists for a sister group relationship with the Coleoptera.

The following cladogram is derived from this:

New winged wing (Neoptera)	Eumetabola    Paraneoptera   Holometabola    remaining orders   NN     Reticulated winged  (Neuropterida)    Camel neck flies (Raphidioptera)   NN    Large winged (Megaloptera)      Reticulated winged (Neuroptera)   Coleopteroid    Beetle (Coleoptera)      Fan winged (Strepsiptera)      Paurometabola

Internal system

Tenomerga mucida as a representative of the Archostemata is one of the most original beetle species

The number of families varies considerably depending on the author and the classic system of beetles is therefore presented very inconsistently.

With over 350,000 species in 179 families , they represent the largest order from the class of insects and are divided into four sub- orders . Investigations based on DNA sequencing have confirmed the delimitation of the subordinates. In the following, only the subordinates are listed, a more detailed representation down to the family level can be found in the article Systematics of the beetles .

• Subordination Archostemata
• Suborder Myxophaga
• Submission to Adephaga
• Subordination to Polyphaga

The group of Archostemata five are families expected that about 50 mainly in tropical and subtropical occurring regions of species included. They are in a sister group relationship to the other three suborders and represent a very old line of beetles with primitive peculiarities, which in its morphology is very similar to the first beetles, which first appeared about 250 million years ago. They have only five abdominal sternites and they also lack the cervical sclerite between the head and prothorax and the external pleurs (lateral chitinous plates) of the prothorax. The hips ( coxa ) of your hind legs are flexible and the thigh rings (trochanters) are usually clearly visible. But they fold their wings just like the species of Myxophaga and Adephaga. They differ from the myxophaga also the fact that the tarsi are not fused with the Prätarsen.

The beetles of the suborder Myxophaga (94 species) live under water and all have in common that their tarsi and pretarsi are fused together. The three-part antennae of the larvae, their five-segment legs, on the last limb of the tarsi there is only one claw, and the growing together of the trochantin , pleuras and the abdominal ventrites of the imagines would indicate a sister group relationship between the Myxophaga and the Polyphaga. On the other hand, the veining and folding of the wings speak for a sister group relationship between Myxophaga and Adephaga.

As the second largest suborder with 14 families, the Adephaga already contain a large variety of species (approx. 37,000). This group is also very old and can be dated back to the Early Triassic approximately 240 million years ago. Some of these are highly specialized species. There are fossil records of both land and aquatic species. The larvae of the Adephaga are adapted to the intake of liquid food, they have an overgrown labrum and no cutting surfaces ( molae ) on the mandibles. In the adults, the pleurs (lateral chitin plates) of the thorax are not fused with the upper side of the pronotum and therefore form a seam. The animals also have six sternas on the abdomen, the first three of which are fused together and divided by the coxae of the hind legs. Many species have defensive glands on the abdomen. It was assumed that the Adephaga are in a sister group relationship to the Myxophaga and Polyphaga, but the latest findings suggest that the Adephaga are more closely related to the Polyphaga.

More than 90 percent of the beetle species (more than 300,000 species) belong to the subordination of the Polyphaga . In the adults, the separation of the pleura of the prothorax and the upper side of the pronotum cannot be seen, but the pleura is fused with the trochantin. This means that a suture between the notum and sternum can be seen on the prothorax; the other suborders have two visible sutures between the sternum and pleurum or between the notum and pleurum. The cervical sclerites between the head and prothorax are present, the coxae of the hind legs are mobile and do not divide the first ventrit, and the wing folding is different from that of the other three suborders. In the three other suborders, cells are formed between radial artery and cubital artery through cross veins, between which the median vein runs and splits. In the Polyphaga there is no cell formation and a maximum of one cross vein between the radius and the median.

The relationships between the four subordinates can be illustrated in the following cladogram:

Beetle	NN    Myxophaga   NN    Adephaga      Polyphaga      Archostemata

Species numbers

Beetles are the most species-rich order of insects, the most species-rich group of organisms (with the possible exception of the prokaryotes ). The number of beetle species described is (depending on the source) given quite consistently with 350,000 to 400,000. This means that 20% to 25% of all known biological species are beetles. Perhaps the most common quote on biodiversity is attributed to the British biologist JBS Haldane (although the quote is probably more famous than he is today):

“There is a story, possibly apocryphal, of the excellent British biologist JBS Haldane, who found himself in the company of a group of theologians. When asked what one can infer about the nature of the Creator from an examination of his creation, he is said to have answered: An inadequate predilection for beetles. "

The most species-rich families of beetles are: weevils (Curculionidae): 51,000 species (superfamily Curculionidea 62,000 species), rump-winged beetles (Staphylinidae): 48,000 species, ground beetles (Carabidae): 40,000 species, leaf beetles (Chrysomelidae): 40,000 species, longhorn beetles (Cerambycidae): 20,000 species , Jewel beetles (Buprestidae): 14,000 species. The most species-rich aquatic group are the swimming beetles (Dytiscidae) with over 4000 species. According to the Red List of 1997, 6,537 beetle species are known from Germany.

The actual number of beetle species is unknown and the subject of intense scientific controversy. It is certain that the vast majority of beetle species live in the tropics, with the Neotropics (South America) obviously being particularly rich in species. Many scientists consider species numbers of up to 5 million to be quite realistic, others estimate the total number no higher than 850,000. In a famous work by the American biologist Terry L. Erwin, he concluded that 7.5 million beetle species (and 30 million arboreal tropical arthropods in general) were extrapolated from the number of species that he examined in detail on a tropical tree species in Panama. Many colleagues consider this estimate to be excessive, even if Erwin defends it after investigations in the Amazon rainforest. A current estimate in 2015, which combines several methods, comes to a global number of species of around 1.5 million beetle species. Every year around 2,300 beetle species are actually described anew, mostly from tropical rainforests.

There is no generally accepted scientific explanation for the particularly high number of beetles. A popular theory explains it as the result of a coevolution with the flowering plants, because phytophagous groups contribute in a special way to biodiversity. The connection is often disputed. According to both the fossil record and the results of the DNA sequencing, the splitting (radiation) of the main groups of beetles seems to be before that of the flowering plants.

Investigations into the number of species are afflicted with many difficulties even for the species described. An unknown number of described species (estimated perhaps 20%) are actually synonyms, i.e. H. the species was described again under a different name. In an approximate overview (after taxonomic revisions in Zoological Records ), Stork and Hine come to the conclusion that 45% of the species treated there are only known from a single place. Of 13%, only a single specimen (usually the type specimen) is known.

Man and beetle

Within entomology ( entomology ) the doctrine of the beetles is called coleopterology . The vast majority of beetles go unnoticed by humans with the exception of coleopterologists. Only a few species that are conspicuous by their size or color, such as cockchafer or ladybird , are known to a larger general public. The less conspicuous species only come into the public eye if they play a special role in people's lives. Most often this is the case when used as pests , pests or else as beneficial organisms occur.

In contrast to other groups of insects, beetles do not play a role as parasites in humans .

Pests

The large oak buck was previously considered a forest pest and is now threatened with extinction in Germany

In agriculture, the storage of particular foods or offer monocultures grown crops occasionally good conditions for the mass propagation of certain species of beetles, so this as pests are considered.

Some species of beetles find sufficient food in a confined space, particularly in camps. Examples of storage pests, primarily in company storage facilities, are grain and rice beetles , while meal beetle larvae are often found in private households.

The potato beetle , the pollen beetle and the western corn rootworm are known to be agricultural pests . In the past few years, the use of transgenic maize has been the subject of controversy in the media to control the corn rootworm .

The American potato beetles and corn rootworms are good examples of beetle species as neozoa . Their biological invasion was prepared by importing and growing their forage crops in Europe. After the animals followed, they found a habitat with good food and no natural enemies, which facilitated their mass distribution.

One beetle whose immigration should still be prevented is the Asian longhorn beetle ( Anoplophora glabripennis ). The beetle attacks numerous tree species and causes them to die. Originally from Asia, the species has already spread to parts of the United States, causing damage of around 150 million US dollars . Similar damage is feared in Europe ; therefore the beetle is classified as a quarantine pest. Its occurrence must be reported to the responsible plant protection service. In the case of previous discoveries, intensive control measures were carried out in the hope of being able to exterminate the original populations.

The indigenous house- goat ( Hylotrupes bajulus ) used to be notifiable throughout Germany according to building regulations . Today it is only in Saxony and Thuringia . The beetle larvae live in built-in softwood, for example in roof trusses. If the infestation is recognized too late, total damage can result. The common rodent beetle ( Anobium punctatum ), known as woodworm, also lives in dead wood . He can be seen as a typical resident of antique furniture .

The bark beetles are one of the major pests in living wood . Best known in Germany is the letterpress printer ( Ips typographus ), which can cause high damage, especially in spruce forests. But bark beetles are also dangerous in natural forests. The mountain pine beetle ( Dendroctonus ponderosae ) , which is also only five millimeters in size , has destroyed over 13 million hectares of forest in western Canada in recent years (for comparison: the forest area in the Federal Republic of Germany is around 11 million hectares). In addition to the high material damage, damage to forests of this magnitude is even feared to have an impact on global warming.

Some species of beetle, such as the large oakbuck ( Cerambyx cerdo ), used to be regional forest pests, but are now threatened with extinction.

Beneficial insects

The Asian ladybug was in many parts of the world for biological pest settled

Apart from the fact that many beetles play an important role in the ecosystem, humans also benefit from some species. The most important of these species include predatory beetles, such as ground beetles , raven-winged beetles and, in particular, ladybirds because they devour insects, mites and snails that are harmful to humans in agriculture and forestry. Certain species of ladybirds are bred en masse against some of the most important agricultural pests. But these leaf- and scale-eating beetles are also useful in gardens . Some types of beetles also play a role in the pollination of plants ( cantharophilia ).

In southern Africa, the San use the hemolymph from the larvae of poison dart beetles to make poison dart . The poison arrows are used for both hunting and tribal wars.

food

→ Main article : Entomophagy in humans

Beetles, mostly in the stage of the grubs, are an important source of food for some peoples in Africa, Asia, South and Central America. In ancient times , some grubs (e.g. the stag beetle) were also consumed as a delicacy in Europe.

A cockchafer soup was known in Germany and France until the middle of the 20th century . In the Magazin für Staatsarzneikunde of 1844, the Medical Councilor Johann Schneider recommended this dish, which is reminiscent of crab soup, as an “excellent and strong food” for which 30 beetles per person are caught, washed and pounded in a mortar, then fried in butter and boiled with broth. And he added that candied cockchafer was a popular dessert among students.

History and art

Egyptian scarab amulet made of steatite, around 550 BC Chr.

Probably the oldest evidence of a beetle depiction, possibly as a symbol of luck, is an approximately 20,000 year old, 1.5 centimeter tall ladybird carved from ivory mammoth , which was probably carried around the neck through a hole with a cord. It was found in Laugerie-Basse in the Dordogne department ( France ).

In ancient times , some naturalists also dealt with beetles, although their consideration was still largely superficial. Aristotle classified beetles based on whether they could hide their wings under a blanket. Today about 112 species of beetles can be identified with some accuracy from ancient tradition. The development of the beetle in several stages was also known for at least several species. The most important sources for the description of the beetles were Aristotle Hesychios and the Roman Pliny the Elder in his natural history . Among other things, they report on subspecies of the barrel beetle, swimming beetle, raven beetle, light beetle, boring beetle, pavement beetle, longhorn beetle, proboscis beetle and leaf horn beetle. In the last genus, the pill roll should be mentioned above all .

The pill turner was considered sacred in ancient Egypt and was called the scarab there. For the Egyptians he was a symbol of the Chepre , a primordial being that had arisen from itself. He was thus also a symbolization of the sun god Re ; his behavior of rolling large balls of dung was a symbol of the course of the sun. To this day it has been handed down in large numbers as mostly stone images. The scarab was also a common handcraft motif. It was depicted as part of amulets, other jewelry or as a seal. It became particularly important from the 18th dynasty, when an increase in production and importance, especially of seal and amulet forms, can be observed. Scarabs were often added to mummies. Like them, the beetles were subjected to the ritual of opening their mouths.

In Aristophanes ' comedy Peace , too , an oversized dung beetle plays a really important role as the mount of the hero Trygaios.

Until the appearance of natural history encyclopedias in the 13th century, the number of known species of beetle decreased to about seven, including bacon beetles , wood borer beetles, dung beetles (scarabs), stag beetles and fireflies . The dung beetles were counted among the Cantharides dangerous for grazing cattle . The firefly was said to have an anti-aphrodisiac effect.

In the literature of the early 20th century, Franz Kafka chose the shape of a beetle (= vermin) for the protagonist Gregor Samsa in the short story The Metamorphosis , in order to symbolize Samsa's failure in his family and in society.

Some beetles still have a special meaning today. For example, the ladybug is valued for its usefulness and is considered a symbol of luck. That is why it is a popular motif on postage stamps , greeting cards and the like. The name ladybird also indicates its importance: Because of their usefulness in biological pest control, the farmers believed that the beetles were a gift from Mary (mother of Jesus) and named them after her.

medicine

Spanish fly ( Lytta vesicatoria )

The medical use of beetles or their ingredients is known, for example the use of cantharidin for blistering plasters, under the name "Cantharis vesicatoria" also in homeopathy and animal homeopathy . It is not possible to increase sexual desire by ingesting ground Spanish flies ( Lytta vesicatoria ).

Novid Beheshti and Andy Mcintosh from the University of Leeds have examined the gas pressure-dependent inlet and outlet valves of the explosion chamber of bombardier beetles and analyzed the process of this flash evaporation . Both the spray distance and the droplet size could be set in a controlled manner, both factors that play an important role in the administration of drugs through aerosol formation . This makes a biologically selected mechanism interesting for medical applications.

Vivaristics

Beetles are also kept and bred as terrarium animals. These are almost exclusively exotic representatives of the rose , giant and stag beetles . In East Asia (especially Japan, Korea and Taiwan), beetle breeding is much more developed than in Central Europe.

Mecynorhina torquata ugandensis - a commonly bred rose beetle

literature

• Bernard Durin: Beetles and other insects. 4th enlarged edition. Schirmer / Mosel, Munich 2013, ISBN 978-3-8296-0631-8 .
• Heinz joy (greeting), Bernhard Klausnitzer (ed.): The beetles of Central Europe. Elsevier, Munich, ISBN 3-334-61035-7 .
• Severa Harde: The Beetle Leader Cosmos. The Central European beetle. Franckh-Kosmos, Stuttgart 2000, ISBN 3-440-06959-1 .
• Bernhard Klausnitzer : Wonderful world of beetles. Herder, Freiburg 1981, ISBN 3-451-19630-1 .
• Sigmund Schenkling : Explanation of the scientific beetle names from Reitterʼs Fauna Germanica , Stuttgart: KG Lutz, 1917, pp. 5–35 ( available online )
• Edmund Reitter : Fauna Germanica - The beetles of the German Empire. (= Digital Library. Volume 134). New movement and facsimile of the 5-volume edition. Stuttgart 1908-1916, Directmedia, Berlin 2006, ISBN 3-89853-534-7 .
• Jiři Zahradnik, Irmgard Jung, Dieter Jung a. a .: Beetles of Central and Northwest Europe. Parey, Berlin 1985, ISBN 3-490-27118-1 .

Web links

Wiktionary: Käfer  - explanations of meanings, word origins, synonyms, translations

Commons : Beetle (Coleoptera)  - Collection of images, videos and audio files

• Edmund Reitter's “Fauna Germanica”, all five volumes
• Determination tables
• Photo collection for pre-determination
• www.koleopterologie.de - photo collection of European and especially Central European beetles
• www.beetle-diversity.com - Photo collection of Southeast Asian beetles (including museum types, English)
• www.kaefer-der-welt.de - Photo collection of beetles from all over the world
• Directory of beetles in Germany, data as a table, distribution in a map of Germany
• Tree of Life Webproject (English)
• The beetle fauna of Germany

Individual evidence

1. ↑ Bernhard Klausnitzer: Wonderful world of the beetles. Herder, Freiburg 1982, ISBN 3-451-19630-1 .
2. ↑ An overview in: Tiit Teder and Toomas Tammaru: Sexual size dimorphism within species increases with body size in insects. In: Oikos. 108, 2005, pp. 321-334.
3. ↑ Jeremy E. Niven, Christopher M. Graham, Malcolm Burrows: Diversity and Evolution of the Insect Ventral Nerve Cord. In: Annual Review of Entomology. 53, 2008, pp. 253-271. doi: 10.1146 / annurev.ento.52.110405.091322
4. ↑ Peter Schneider, Bruno Krämer: The control of the flight with the tiger beetle (Cicindela) and with the cockchafer (Melolontha). In: Journal of Comparative Physiology A: Neuroethology, Sensory, Neural, and Behavioral Physiology. 91, number 4, December 1974, pp. 377-386.
5. ↑ Jayne E. Yack: The Structure and Function of Auditory Chordotonal Organs in Insects. In: Microscopy Research and Technique . 63, 2004, pp. 315-337. doi: 10.1002 / jemt.20051
6. ^ TG Forrest, MP Read, HE Farris, RR Hoy: A tympanal hearing organ in scarab beetles. In: Journal of Experimental Biology. 200, 1997, pp. 601-606.
7. ↑ K. Peschke, P. Hahn, D. Fuldner: Adaptions of the blow fly parasitiod Aleochara curtula to the temporarial availability of hosts at a carrion. In: Zool. Jb. Syst. 114, 1987, pp. 471-486.
8. ^ Rolf G. Beutel, Richard AB Leschen: Handbuch der Zoologie - Coleoptera, Beetles, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim) . 1st edition. de Gruyter , 2005, ISBN 3-11-017130-9 (English).
9. ^ Richard AB Leschen, Rolf G. Beutel, John F. Lawrence: Handbuch der Zoologie - Coleoptera, Beetles, Volume 2: Morphology and Systematics (Elateroidea, Bostrichiformia, Cucujiformia partim) . de Gruyter, 2010, ISBN 978-3-11-019075-5 (English).
10. ↑ Toby Hunt et al .: A comprehensive phylogeny of Beetles reveals the evolutionary origins of a superradiation. In: Science. 318, 21, 2007, pp. 1913-1916. (PDF; 2.4 MB)
11. ↑ ^{a b c d} Peter S. Cranston, Penny J. Gullan: Phylogeny of Insects. In: Vincent H. Resh, Ring T. Cardé (Ed.): Encyclopedia of Insects. Academic Press, Amsterdam 2003, ISBN 0-12-586990-8 . (online) ( Memento from February 4, 2012 in the Internet Archive )
12. ↑ The quote goes back to: Hutchinson, George Evelyn: Homage to Santa Rosalia or why are there so many kinds of animals? In: American Naturalist. 93, 1959, pp. 145-159. Contemporaries testify that Haldane made the quote his own and passed the story on.
13. ^ Rolf G. Oberprieler, Adriana E. Marvaldi, Robert S. Anderson: Weevils, weevils, weevils everywhere. In: Z.-Q. Zhang, WA Shear (Ed.): Linnaeus Tercentenary: Progress in Invertebrate Taxonomy. (= Zootaxa. 1668). 2007, ISBN 978-1-86977-180-5 , pp. 491-520.
14. ↑ RG Beutel, RAB Leschen (Ed.): Coleoptera, Beetles. Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga partim). (= Handbook of Zoology. Vol. IV). Walter de Gruyter, Berlin / New York 2005.
15. ↑ Viktor Nilsson-Örtman, Anders N. Nilsson: Using taxonomic revision data to estimate the global species richness and characteristics of undescribed species of Diving Beetles (Coleoptera: Dytiscidae). In: Biodiversity Informatics. 7, 2010, pp. 1-16.
16. ↑ TL Erwin: Tropical Forests: Their Richness in Coleoptera and other Arthropod Species. In: The Coleopterists Bulletin. 36 (1), 1982, pp. 74-75.
17. ^ Nigel E. Stork, James McBroom, Claire Gely, Andrew J. Hamilton (2015): New approaches narrow global species estimates for beetles, insects, and terrestrial arthropods. In: PNAS Proceedings of the National Academy of Sciences USA. vol. 112, no. 24, 2015, pp. 7519-7523. doi: 10.1073 / pnas.1502408112
18. ↑ Reinhard Wandtner: Bark beetles sabotage climate protection. In: faz.net. April 27, 2008.
19. ↑ HD Neuwinger: African Ethnobotany: Poisons and Medicines. ( Memento from March 14, 2012 in the Internet Archive ) Neuwinger-online.de.
20. ↑ CE Mbah, GOV Elekima: Nutrient composition of some terrestrial insects in Ahmadu Bello University, Samaru Zaria Nigeria. In: Science World Journal. 2, No. 2, 2007, pp. 17-20.
21. ↑ JO Fasoranti, DO Ajiboye: Some edible insects of Kwara state, Nigeria. In: American Entomologist. 39, No. 2, 1993, pp. 113-116.
22. ↑ FS Agbidye, TI Ofuya, SO Akindele: Some edible insect species consumed by the people of Benue State, Nigeria. In: Pakistan Journal of Nutrition. 8, No. 7, 2009, pp. 946-950.
23. ^ Western Attitudes towards insects as food: Europe, the United States, Canada. ( Memento from December 28, 2015 in the web archive archive.today ) Chapter 9, viewed May 11, 2015.
24. ↑ Gene R. DeFoliart: Insects as Food: Why the Western attitude is important. In: Annu. Rev. Entomol. 44, 1999, pp. 27-50, p. 40.
25. ^ Bernhard Klausnitzer , Hertha Klausnitzer: Ladybirds (Coccinellidae). Westarp Sciences, Magdeburg 1997, ISBN 3-89432-812-6 .
    Figure see Fig. 1 in: kerbtier.de , accessed on May 14, 2015.
26. ↑ For the beetles in antiquity, see Christian Hühnemörder: Käfer. In: DNP . Volume 6, 1999, pp. 132-134.
27. ↑ For the meaning in the ancient Egyptian culture see Walter F. Reineke: Skarabäus. In: Helmut Freydank u. a .: Lexicon of the Old Orient. VMA, Wiesbaden 1997, ISBN 3-928127-40-3 , p. 403 f.
28. ↑ For beetles in the Middle Ages, see Christian Hühnemörder: Käfer. In: Hiera means to Lucania. (=. Lexicon of the Middle Ages . Volume 5). dtv, Munich 2002, ISBN 3-423-59057-2 , Sp. 848.
29. ↑ Novid Beheshti, Andy C. Mcintosh: The bombardier beetle and its use of a pressure relief valve system to deliver a periodic pulsed spray. In: Bioinspiration and Biomimetics. 2, No. 4, 2007, doi: 10.1088 / 1748-3182 / 2/4/001 .
30. ↑ Bombardier Beetle: The Gemheimnis of poison sprayer , focus.de, April 2nd of 2008.
31. ↑ Aquazoo Löbbecke Museum - keeping and breeding insects: Käfer , duesseldorf.de, accessed on June 1, 2016.

This article was added to the list of excellent articles on June 10, 2008 in this version .