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Beetle

2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and
Fish

                       iBeetles
   Colorado potato beetle, Leptinotarsa decemlineata
   Colorado potato beetle, Leptinotarsa decemlineata
               Scientific classification

   Kingdom:    Animalia
   Phylum:     Arthropoda
   Class:      Insecta
   Subclass:   Pterygota
   Infraclass: Neoptera
   Superorder: Endopterygota
   Order:      Coleoptera
               Linnaeus, 1758

                                  Suborders

   Adephaga
   Archostemata
   Myxophaga
   Polyphaga
   See subgroups of the order Coleoptera

   Beetles are the most diverse group of insects. Their order, Coleoptera
   (meaning "sheathed wing"), has more described species in it than in any
   other order in the animal kingdom. Forty percent of all described
   insect species are beetles (about 350,000 species), and new species are
   regularly discovered. Estimates put the total number of species,
   described and undescribed, at between 5 and 8 million. This is why J.
   B. S. Haldane, a Scottish geneticist, asked what his studies of nature
   revealed about God, replied, "An inordinate fondness for beetles."

   Beetles can be found in almost all habitats, but are not known to occur
   in the sea or in the polar regions. They impact the ecosystem in
   several ways. On the one hand, they feed on plants and fungi, break
   down animal and plant debris, and eat other invertebrates. On the other
   hand, they are prey of various animals including birds and mammals.
   Certain species are agricultural pests, such as the red flour beetle
   Tribolium castaneum, the Colorado potato beetle Leptinotarsa
   decemlineata, or the mungbean beetle Callosobruchus maculatus Fabr,
   while others are important controls of agricultural pests. For example,
   lady beetles (family Coccinellidae) consume aphids, scale insects,
   thrips, and other plant-sucking insects that damage crops.

Anatomy

   The general anatomy of beetles is quite uniform, though specific organs
   and appendages may vary greatly in appearance and function between the
   many families in the order. Beetle bodies are divided into three
   sections: the head, the thorax, and the abdomen. Like all insects,
   beetles are segmented organisms, and all three of the major sections of
   the body may themselves be composed of several further segments,
   although these are not always readily discernable.

   Beetles are generally characterised by a particularly hard exoskeleton
   and hard forewings ( elytra). The beetle's exoskeleton is made up of
   numerous plates called sclerites, separated by thin sutures. This
   design creates the armoured defences of the beetle while maintaining
   flexibility. The elytra are not used for flight, but tend to cover the
   hind part of the body and protect the second pair of wings ( alae).
   Elytra must generally be raised in order to move the hind flight wings.
   A beetle's flight wings are crossed with veins and, after landing, are
   folded, often along these veins, and stored below the elytra. In some
   beetles the ability to fly has been lost, most notably in the ground
   beetles (family Carabidae) and the true weevils (family Curculionidae),
   but also in some desert and cave-dwelling species of other families.
   Many of these species have the two elytra fused together, forming a
   solid shield over the abdomen. In a few families both the ability to
   fly and the elytra have been lost, with the best known example being
   the glowworms of the family Phengodidae, in which the females are
   larviform throughout their lives.

   Beetles have mouthparts similar to those of grasshoppers. Of these
   parts, the most commonly known are likely the mandibles, which appear
   as large pincers on the front of some beetles. The mandibles are a pair
   of hard, often tooth-like structures that move horizontally to grasp,
   crush, or cut food or enemies (see Predation, below). Two pairs of
   finger-like appendages are found around the mouth in most beetles,
   serving to move food into the mouth. These are the maxillary and labial
   palpi.

   The eyes are compound, and may display remarkable adaptability, as in
   the case of whirligig beetles (family Gyrinidae), in which the eyes are
   split to allow a view both above and below the waterline. Other species
   also have divided eyes (some Cerambycidae and Curculionidae), while
   many beetles have eyes that are notched to some degree. A few beetle
   genera also possess ocelli, which are small, simple eyes usually
   situated farther back on the head (on the vertex).

   Beetle antennae are primarily organs of smell, but may also be used to
   physically feel out a beetle's environment. Further, they may be used
   in some families during mating, or among a few beetles for defence.
   Antennae vary greatly in form within the Coleoptera, but are often
   similar within any given family. In some cases males and females of the
   same species will have different antennal forms. Antennae may be
   clavate ( flabellate and lamellate are sub-forms of clavate, or clubbed
   antennae), filiform, geniculate, moniliform, pectinate, or serrate. For
   images of these antennal forms, see antenna (biology)

   The legs, which are multi-segmented, end in two to five small segments
   called tarsi, which are vaguely comparable to feet. Like many other
   insect orders beetles bear claws, usually one pair, on the end of the
   last tarsal segment of each leg. While most beetles use their legs for
   walking, legs may be variously modified and adapted for other uses.
   Among aquatic families (Dytiscidae, Haliplidae, many Hydrophilidae, and
   others) the legs, most notably the hind pair, are modified for swimming
   and often bear rows of long hairs to aid this purpose. Other beetles
   have fossorial legs that are widened and often spined for digging.
   Species with such adaptations are found among the scarabs, ground
   beetles, and clown beetles (family Histeridae). The hind legs of some
   beetles, such as flea beetles (within Chrysomelidae) and flea weevils
   (within Curculionidae), are enlarged and designed for jumping.

   Oxygen is obtained via a tracheal system. Air enters a series of tubes
   along the body through openings called spiracles, and is then taken
   into increasingly finer fibres. Pumping movements of the body force the
   air through the system.

   Beetles have hemolymph instead of blood, and the open circulatory
   system of the beetle is powered by a tube-like heart attached to the
   top inside of the thorax.

Physiology

   There are few things that a beetle somewhere will not eat; even
   inorganic matter may be consumed. Some beetles are highly specialised
   in their diet; for example, the Colorado potato beetle, Leptinotarsa
   decemlineata, almost exclusively colonizes plants of the potato family
   ( Solanaceae). Others are generalists, eating both plants and animals.
   Ground beetles (family Carabidae) and rove beetles (family
   Staphylinidae), among others, are entirely carnivorous and will catch
   and consume other arthropods and small prey such as earthworms and
   snails. Decaying organic matter is a primary diet for many species.
   This can range from dung, which is consumed by coprophagous species
   such as certain scarab beetles (family Scarabaeidae), to dead animals,
   which are eaten by necrophagous species such as the carrion beetles
   (family Silphidae).

   Various techniques are employed for retaining both air and water
   supplies. For example, predaceous diving beetles (family Dytiscidae)
   employ a technique of retaining air, when diving, between the abdomen
   and the elytra.

Development

   Scarabaeiform larva of the cockchafer, Melolontha melolontha
   Enlarge
   Scarabaeiform larva of the cockchafer, Melolontha melolontha

   Beetles are endopterygotes with complete metamorphosis.

   Although beetle eggs are generally very small, their size, shape,
   colour, and content vary extensively among species, as is generally the
   case for most sexually reproducing species. A single female may lay
   from several dozen to several thousand eggs during its life time. Eggs
   are usually laid according to the substrate the larva will feed on upon
   hatching. Among others, they can be laid loose in the substrate (e.g.
   flour beetle), laid in clumps on leafs (e.g. Colorado potato beetle),
   or individually attached (e.g. mungbean beetle and other seed borer) or
   buried in the medium (e.g. carrot weevil).

   The larvae of beetles are usually the principal feeding stage of the
   lifecycle. Larvae tend to feed voraciously once they emerge from their
   eggs. Some feed externally on plants, such as those of certain leaf
   beetles, while others feed within their food sources (most metallic
   wood-boring beetles and longhorn beetles). The larvae of many beetle
   families are predatory like the adults (ground beetles, lady beetles,
   rove beetles). The larval period varies between species but can be as
   long as several years.

   Beetle larvae can be differentiated from other insect larvae by their
   hardened, often darkened head, the presence of chewing mouthparts, and
   spiracles along the sides of the body. Like adult beetles, the larvae
   are varied in appearance, particularly between beetle families. Beetles
   whose larvae are somewhat flattened and are highly mobile are the
   ground beetles, some rove beetles, and others; their larvae are
   described as campodeiform. Some beetle larvae resemble hardened worms
   with dark head capsules and minute legs. These are elateriform larvae,
   and are found in the click beetle (Elateridae) and darkling beetle
   (Tenebrionidae) families. Some elateriform larvae of click beetles are
   known as wireworms. Beetles in the families of the Scarabaeoidea have
   short, thick larvae described as scarabaeiform, but more commonly known
   as grubs.

   All beetle larvae go through several instars, which are the
   developmental stages between each moult. In many species the larvae
   simply increase in size with each successive instar. In some cases,
   however, more dramatic changes occur. Among certain beetle families or
   genera, particularly those that exhibit parasitic lifestyles, the first
   instar (the planidium) is highly mobile in order to search out a host,
   while the following instars are more sedentary and remain on or within
   their host. This is known as hypermetamorphosis; examples include the
   blister beetles (family Meloidae) and some rove beetles, particularly
   those of the genus Aleochara.

   As with all endopterygote insects, beetle larvae pupate for a period of
   time, and from the pupa emerges a fully formed, sexually mature adult
   beetle, or imago. Adults have an extremely variable lifespan, from
   weeks to years, depending on the species.

Reproduction

   Beetles may display extremely intricate behaviour when mating. Smell is
   thought to be important in the location of a mate.

   Conflict can play a part in the mating rituals of species such as
   burying beetles (genus Nicrophorus) where conflicts between males and
   females rage until only one of each is left, thus ensuring reproduction
   by the strongest and fittest. Many beetles are territorial and will
   fiercely defend their small patch of territory from intruding males.

   Pairing is generally short but in some cases will last for several
   hours. During pairing sperm cells are transferred to the female to
   fertilise the egg.
   Striped love beetle Eudicella gralli from the forests of Central
   Africa. The iridescent wing cases are used in marriage ceremonies.
   Enlarge
   Striped love beetle Eudicella gralli from the forests of Central
   Africa. The iridescent wing cases are used in marriage ceremonies.

Parental care

   Parental care varies between species, ranging from the simple laying of
   eggs under a leaf to certain scarab beetles, which construct impressive
   underground structures complete with a supply of dung to house and feed
   their young.

   There are other notable ways of caring for the eggs and young, such as
   those employed by leaf rollers, who bite sections of leaf causing it to
   curl inwards and then lay the eggs, thus protected, inside.

Predation

   Beetles and their larvae have a variety of strategies to avoid being
   eaten, for example using camouflage to avoid being spotted by
   predators. These include the leaf beetles (family Chysomelidae) that
   have a green colouring very similar to their habitat on tree leaves.
   More complex camouflage also occurs, as with some weevils (family
   Curculionidae), where various coloured scales or hairs cause the beetle
   to resemble bird dung.

   A number of longhorn beetles (family Cerambycidae) bear a striking
   resemblance to wasps. This defense, known as mimicry, can be found to a
   lesser extent in other beetle families, such as the scarab beetles.

   Many species, including lady beetles and blister beetles, can secrete
   poisonous substances to make them unpalatable. These same species often
   exhibit aposematism, where bright or contrasting colour patterns warn
   away potential predators.

   Large ground beetles will tend to go on the attack, using their strong
   mandibles to forcibly persuade a predator to seek out easier prey.

Evolutionary history and classification

   Beetles entered the fossil record during the Lower Permian, about 265
   million years ago.

   The four extant suborders of beetle are these:
     * Polyphaga is the largest suborder, containing more than 300,000
       described species in more than 170 families, including rove beetles
       (Staphylinidae), scarab beetles (Scarabaeidae), blister beetles
       (Meloidae), stag beetles (Lucanidae), and true weevils
       (Curculionidae). These beetles can be identified by the cervical
       sclerites (hardened parts of the head used as points of attachment
       for muscles) absent in the other suborders.
     * Adephaga contains about 10 families of predatory beetles, includes
       ground beetles (Carabidae), predacious diving beetles (Dytiscidae)
       and whirligig beetles (Gyrinidae). In these beetles the testes are
       tubular and the first abdominal sternum (a plate of the
       exoskeleton) is divided by the hind coxae (the basal joints of the
       beetle's legs).
     * Archostemata contains four families of mainly wood-eating beetles,
       including reticulated beetles (Cupedidae) and telephone-pole
       beetles (Micromalthidae).
     * Myxophaga contains about 100 described species in four families,
       mostly very small, including skiff beetles (Hydroscaphidae) and
       minute bog beetles (Sphaeriusidae).

   These suborders diverged in the Permian and Triassic. Their
   phylogenetic relationship is uncertain, with the most popular
   hypothesis being that Polyphaga and Myxophaga are most closely related,
   with Adephaga an outgroup to those two, and Archostemata an outgroup to
   the other three.

   The large number of beetle species poses special problems for
   classification, with some families consisting of thousands of species
   and needing further division into subfamilies and tribes.

   See the article subgroups of the order Coleoptera for a complete list
   of families and for a complete list of World families and subfamilies.

Impact on humans

Pests

   Damage to beans by larvae of the common bean weevil, Acanthoscelides
   obtectus
   Enlarge
   Damage to beans by larvae of the common bean weevil, Acanthoscelides
   obtectus

   Many agricultural, forestry, and household pests are represented by the
   order. These include:
     * The Colorado potato beetle, Leptinotarsa decemlineata, is a
       notorious pest of potato plants. Crops are destroyed and the beetle
       can only be treated by employing expensive pesticides, many of
       which it has begun to develop immunity to. As well as potatoes,
       suitable hosts can be a number of plants from the potato family (
       Solanaceae), such as nightshade, tomato, aubergine and capsicum.
     * The bark beetles Hylurgopinus rufipes and Scolytus multistriatus,
       and the elm leaf beetle, Pyrrhalta luteola, attack elm trees. The
       bark beetles are important elm pests because they carry Dutch elm
       disease as they move from infected breeding sites to feed on
       healthy elm trees. The spread of the fungus by the beetle has led
       to the devastation of elm trees in many parts of the Northern
       Hemisphere, notably in Europe and North America.
     * The death watch beetle, Xestobium rufovillosum, (family Anobiidae)
       is of considerable importance as a pest of older wooden buildings
       in Britain. It attacks hardwoods such as oak and chestnut, always
       where some fungal decay has taken or is taking place. It is thought
       that the actual introduction of the pest into buildings takes place
       at the time of construction.
     * Asian long-horned beetle
     * Citrus long-horned beetle

Beneficial organisms

     * Both the larvae and adults of some lady beetles (family
       Coccinellidae) are found in aphid colonies. Other lady beetles feed
       on scale insects. If normal food sources are scarce they may feed
       on other things, such as small caterpillars, young plant bugs,
       aphid honeydew, and plant nectar.
     * Ground beetles (family Carabidae) are common predators of many
       different insects and other arthropods, including fly eggs,
       caterpillars, and other pest insects.

   Some farmers introduce beetle banks to foster and provide cover for
   beneficial beetles.

Scarab beetles in Egyptian culture

   Ancient Egyptian scene depicting a scarab beetle
   Enlarge
   Ancient Egyptian scene depicting a scarab beetle

   Several species of the dung beetles, most notably Scarabaeus sacer
   (often referred to as "scarab"), enjoyed a sacred status among the
   ancient Egyptians, as the creatures were likened to the god Khepri.
   Some scholars suggest that the people's practice of making mummies was
   inspired by the brooding process of the beetle.

   Many thousands of amulets and stamp seals have been excavated that
   depict the scarab. In many artifacts, the scarab is depicted pushing
   the sun along its course in the sky. During and following the New
   Kingdom, scarab amulets were often placed over the heart of the
   mummified deceased. The amulets were often inscribed with a spell from
   the Book of the Dead which entreated the heart, "Do not stand as a
   witness against me."

Study and Collection

   Beetle collection at the Melbourne Museum, Australia
   Enlarge
   Beetle collection at the Melbourne Museum, Australia

   The study of beetles is called coleopterology, and its practitioners
   are coleopterists. See the list of notable coleopterists for more
   information.

   Coleopterists have formed organizations to facilitate the study of
   beetles. Among these is The Coleopterists Society, an international
   organization based in the United States.

   Research in this field is often published in peer-reviewed journals
   specific to the field of coleopterology, though journals dealing with
   general entomology also publish many papers on various aspects of
   beetle biology. Some of the journals specific to beetle research are:
     * The Coleopterist (United Kingdom beetle fauna)
     * The Coleopterists Bulletin (published by The Coleopterists Society)

   There is a thriving industry in the collection of beetle specimens for
   amateur and professional collectors. Some countries have established
   laws governing or prohibiting the collection of certain rare (and often
   much sought after) species.

Gallery

   Varied carpet beetle

   Lady beetle

   Tiger beetle

   South African dung beetle

   Emerald ash borer

   Flea beetle

   Japanese beetle

   Colorado potato beetle larvae

   Spotted flower chafer

   Prionus californicus

   Pelidnota punctata

   Bess beetle

   Longhorn beetle Parandra brunnea

   Acrocinus longimanus

   Drugstore beetle Stegobium paniceum

   A weevil

   A Hispid

   Rhinoceros beetle and a coin

   Stag beetle

   A shiny blue scarab beetle

   Anthia sexguttata a carabid beetle

   Retrieved from " http://en.wikipedia.org/wiki/Beetle"
   This reference article is mainly selected from the English Wikipedia
   with only minor checks and changes (see www.wikipedia.org for details
   of authors and sources) and is available under the GNU Free
   Documentation License. See also our Disclaimer.
