Beetles (Coleoptera)

The body of an adult beetle is composed, like all insects, of three regions: head, thorax, and abdomen. What is visible in dorsal view in beetles, though, is the head, prothorax, and elytra (singular, elytron), which cover the meso- and metathorax, and usually all of the abdomen

The head bears the eyes, chewing mouthparts, and usually 11-segmented antennae. The size and placement of the compound eyes varies widely within the order, and eyelessness is fairly frequent, especially in soil and litter inhabiting beetles, and those which dwell in caves. The presence of ocelli occurs in only a very few small groups. Mouthparts may be borne on the end of a rostrum (most notably in weevils, Curculionidae). Beetles exhibit almost endless modifications of the mouthparts, especially of the mandibles, which may be the most striking feature of the individual, as in Lucanidae and some Cerambycidae. The antennae in beetles range from simply threadlike (filiform) or beadlike (moniliform), to gradually (clavate) or abruptly (capitate) clubbed, or saw-like (serrate), or with the club segments asymmetrically developed and capable of opening and closing like a fan (lamellate), or elbowed like an ant’s antennae (geniculate), or feathery (pectinate or flabellate). Although most beetles have 11-segmented antennae, reduction in the number of segments (to only one or two segments in extreme examples) is common, while an increase in the number of segments is quite uncommon

The thorax is composed of three parts: the prothorax bears the forelegs; the mesothorax gives rise to the forewings, or elytra, and the middle legs; the metathorax bears the hind wings and hindlegs. The legs are five-segmented, composed of (from closest to the body) the coxa, trochanter, femur, tibia, and tarsus. The tarsus is composed primitively of five tarsomeres, but this is often reduced and the tarsal formula (the number of tarsomeres on the front, middle, and hind legs) is important in beetle identification. The elytra generally completely cover the dorsal part of the metathoraz and abdomen, but are secondarily short in many groups (Staphylinidae, Silphidae, Cerambycidae, etc.). They almost always meet in a straight line, one of the very few exceptions being the genus Meloe in the Meloidae

The dorsal part of the abdomen is usually soft, except in those groups with abbreviated elytra; the ventral surface of the abdomen is almost always heavily sclerotized

Beetles undergo complete metamorphosis. The life cycle of the typical beetle includes egg, three to five larval instars, pupa, and adult. A few beetle families have more complicated life histories: Micromalthidae have multiple larval forms and paedogenesis (reproduction by larvae); several families, e.g., Meloidae, Ripiphoridae, Passandridae, undergo hypermetamorphosis, with the first instar larva being considerably different from succeeding instars. The length of the life cycle varies widely within the order, but generation length of most beetles falls within a few weeks to one or two years. A few beetles, notably some Cerambycidae, under extraordinary conditions can spend decades as larvae

It is generally agreed the beetles are most closely related to the neuropteroid orders. The first fossils of true Coleoptera date back to the Triassic. They were preceded by a group of beetle-like insects called the Protocoleoptera that arose in the Lower Permian. By the Jurassic, many modern families had arisen, and most of the rest appeared during the Cretaceous, coincident with the rise of the flowering plants. Interestingly, many of the Cenozoic amber fossils can be attributed to modern genera

Beetles were recognized as a distinct group of insects as far back as the ancient Greeks, but the classification within the group has been in a state of flux up to the present day. The limits of the order are well understood, with the only issue being whether to include or exclude the twisted-wing parasites (Strepsiptera). Most now treat them as a separate order near Coleoptera, but some have argued that their true affinities lie with the Diptera. Within the Coleoptera, the general classification is fairly well accepted but disagreement persists on the ranking or placement of some family-level groups. The classification presented here is that used in the two-volume American Beetles (Arnett and Thomas 2000, Arnett et al. 2002), the most recently published, major general work on beetles

There are 166 families of beetles in the world; 131 of those occur in America north of Mexico. The order is divided very unequally into four suborders: Archostemata, Myxophaga, Adephaga, and Polyphaga.

Some representative beetles: top left, drugstore beetle, Stegobium paniceum (Anobiidae); top right, lesser grain borer, Rhyzopertha dominica (Bostrichidae); second row left, cowpea weevil, Callosobruchus maculatus (Bruchidae); second row right, Buprestis lineatus (Buprestidae); third row left, Pasimachus sublaevis (Carabidae); third row right, banded hickory borer, Knulliana cincta (Cerambycidae); bottom left, Trirhabda bacharidis (Chrysomelidae); bottom right, Cicindela punctulata (Carabidae) (photos by Lyle Buss).

Full size image

Some additional representative beetles: top left, Neorthopleura thoracica (Cleridae); top right, Mexican bean beetle, Epilachna varivestis (Coccinellidae); second row left, eyed click beetle, Alaus oculatus (Elateridae); second row right, maize weevil, Sitophilus zeamais (Curculionidae); third row left, striped blister beetle, Epicauta vittata (Meloidae); third row right, a firefly, Photinus tanytoxus (Lampyridae); bottom left, a rove beetle, Platydracus fossator (Staphylinidae); bottom right, Hercules beetle, Dynastes titus (Scarabaeidae) (Dynastes and Epilachna by Jim Castner; other photos by Lyle Buss).

Full size image

Archostemata

Only four families comprise this primitive suborder. Beetles very similar to present-day Cupedidae are known from the Lower Triassic. Two families, Cupedidae and Micromalthidae, are known from the Nearctic. Most are found in decaying wood. The sole member of Micromalthidae, Micromalthus debilis LeConte, has an unusual and complex life history, including paedogenesis

Myxophaga

Another four families have been assigned to this, the most recently recognized suborder. Two families, Microsporidae and Hydroscaphidae, occur in the Nearctic. The few minute species are associated with algae

Adephaga

Nine families comprise this suborder, the only one that is composed exclusively (except for one small family of wood-inhabiting beetles, the Rhysodidae) of predacious beetles. Eight families occur in the Nearctic, the Carabidae or ground beetles, being by far the largest family in the suborder, with 2,635 species and subspecies being recorded from the Nearctic and about 40,000 for the world. Carabids often are found on the ground under stones or logs, or in leaf litter, but many, especially in the tropics, are arboreal. They are usually small to moderate in size. Most are darkly colored, but many exhibit brilliant metallic colors. Most ground beetles are predacious, feeding on soft-bodied insects, but some are specialized predators of snails and millipeds. A few are seed feeders. Beetles in most of the other families spend most of their lives in fresh water

Polyphaga

All the rest of the beetle families are assigned to this suborder. It has been subdivided into several series and numerous superfamilies

Series: Staphyliniformia

This series is composed of two superfamilies

Superfamily: Hydrophiloidea

Three families, two moderately sized and one small, comprise this superfamily. The Hydrophilidae are predominantly predacious and aquatic. The Histeridae and Sphaeritidae are terrestrial and predacious

Superfamily: Staphylinoidea

This family contains six small or moderate-sized families and one huge one, the Staphylinidae, which has more than 4,100 species in the Nearctic and more than 46,000 worldwide. All the families occur in the Nearctic. Staphylinids, or rove beetles, often are found around decaying vegetable material and dead animals, where they feed on fly larvae and other insects. Many staphylinids live in the nests of social insects, ants and termites primarily, and show many physical and behavioral adaptations to that way of life. Most staphylinids have very short elytra and flexible abdomens

Series: Scarabaeiformia

This series contains only the single superfamily

Superfamily: Scarabaeoidea

This superfamily contains 11 small or moderate-sized families and one very large one, the Scarabaeidae. There are more than 27,800 species of scarab beetles in the world; about 1,700 occur in the Nearctic. This superfamily includes the relatively small but well-known Lucanidae (stag beetles) and Passalidae (bess beetles). The Scarabaeidae include some of the largest known beetles, such as the members of the genera Dynastes and Megasoma in the New World, and Goliathus in tropical Africa. Males of many scarabs bear spectacular horns on the head and/or pronotum with which they battle each other for females. Scarab beetles have extremely diverse feeding habits. Many feed on dung of mammals, some being extremely specific on the kind of dung they will accept. Dung beetles provision burrows with dung for their larvae, some rolling balls of dung away for burying and sculpting the dung ball into special shapes. Some even tend the dung to prevent the growth of mold on it. Many others feed in soil, humus, and decaying wood. Some, like the Japanese beetle Popilia japonica Newman, feed on living plants and are economic pests of extreme importance. Many others are found in nests of social insects, primarily ants and termites

Series: Elateriformia

This series contains five mostly small superfamilies

Superfamily: Scirtoidea

Four families, three of which are found in the Nearctic, comprise this superfamily. Two families, Eucinetidae and Clambidae, contain small to minute beetles that are found in leaf litter and apparently feed on fungus. Scirtidae are aquatic as larvae and adults generally are found in wet habitats

Superfamily: Dascilloidea

Only two small families, Dascillidae and Rhipiceridae, comprise this superfamily. Larvae of Rhipiceridae are hypermetamorphic and parasitic on immature annual cicadas (Heteroptera)

Superfamily: Buprestoidea

Two families, Schizopodidae and Buprestidae, are included in this superfamily. The Schizopodidae are a small family, confined to the western Nearctic. The Buprestidae are one of the larger families of Coleoptera, with 788 species and subspecies recorded from the Nearctic and more than 14,000 in the world. These often brilliantly colored beetles are mostly wood borers as larvae, although some are leaf miners. A few are of economic importance

Superfamily: Byrrhoidea

There are 12 mainly small families assigned here; most of the species are aquatic or subaquatic. All but one of the families are found in the Nearctic. The water penny beetles, Psephenidae, with their remarkably flattened larvae, are found on rocks in streams

Superfamily: Elateroidea

Fifteen rather diverse families comprise this superfamily, all but three of which are found in the Nearctic. The largest family is the Elateridae, or click beetles. There are about 10,000 species of click beetles in the world, with 965 recorded from the Nearctic. Click beetles (and a few of the other families) bear a ‘click’ mechanism on the pro- and mesosternum that allows them to fling themselves into the air with some force if they are placed on their backs. Members of one mostly tropical group of click beetles are luminescent. Other large or widely distributed families include the Lampyridae, Lycidae, Cantharidae, and Eucnemidae

Series: Bostrichiformia

The series includes two small superfamilies, plus the Jacobsoniidae, which have not been placed in a superfamily

Superfamily: Derodontoidea

Only the Derodontidae are included in this superfamily. They are found on slime molds

Superfamily: Bostrichoidea

Four families are included here, Nosodendridae, Dermestidae, Bostrichidae, and Anobiidae. The last three including many economically important pests of animal products such as wool, leather, feathers, and silk (Dermestidae) and stored products and wood or wood products (Bostrichidae and Anobiidae)

Series: Cucujiformia

This huge series contains the rest of the Coleoptera, arranged in 6 superfamilies

Superfamily: Lymexyloidea

This superfamily contains only the ship-timber beetles, Lymexylidae, a small group of soft-bodied, wood-boring beetles

Superfamily: Cleroidea

Three moderate-sized families of predominantly predacious beetles comprise this superfamily

Superfamily: Cucujoidea

This is a large superfamily composed of 31 mostly small to moderate-sized families, 10 of which do not occur in the Nearctic. Members of most of the families are associated with fungus, but some are predominantly predacious, such as the largest and best-known family, Coccinellidae, and a few (Bothrideridae and Passandridae) even contain species which have parasitic larvae

Superfamily: Tenebrionoidea

This is the second largest superfamily with 30 families, six of which do not occur in the Nearctic. Most of the families are small to moderate in size, but the Tenebrionidae are one of the largest families of Coleoptera, with about 19,000 species worldwide and about 1,100 in the Nearctic. Although the Tenebrionidae are found in all kinds of habitats, the family is especially well represented in deserts. They are usually sombre in coloration, hence their common name of darkling beetles, and often are found on the ground under rocks and logs

Superfamily: Chrysomeloidea

The superfamily contains five families, two of which are very large. The longhorn beetles, Cerambycidae, contains more than 20,000 species worldwide and more than 900 in the Nearctic. They are generally elongate, handsome beetles with long to very long antennae. Most are associated with dead or dying woody plants, although some attack living trees. Many are of economic importance. Some very large forms occur in the tropics and are among the largest beetles. The leaf beetles, Chrysomelidae, include about 35,000 species worldwide and about 1,720 in the Nearctic. Chrysomelids differ from cerambycids in usually being smaller, less elongate, and with shorter antennae. Often they are brightly colored. Leaf beetles are associated predominantly with living plants, feeding on the foliage and roots. Many are economically important pests of agriculturally important crops. The seed beetles, Bruchidae, often are combined with the leaf beetles. Several are important pests of stored legume seeds

Superfamily: Curculionoidea

The largest family of living organisms is included among the eight families in this superfamily. The weevils, Curculionidae, contain more than 60,000 species worldwide and about 2,400 in the Nearctic. As presently defined, the Curculionidae are restricted to curculionoids with geniculate antennae. They are almost entirely herbivorous, attacking all parts of all kinds of plants. Many of the worst agricultural pests are weevils. The Brentidae, or primitive weevils, are mostly tropical but one oak pest occurs in the eastern Nearctic. The Anthribidae, or fungus weevils, are associated with fungi of various kinds

• Suborder: ARCHOSTEMATA Kolbe 1908

• Cupedidae Laporte 1836, The reticulated beetles

• Ommatidae Sharp and Muir 1912

• Crowsonellidae Iablokoff-Khnzorian 1983

• Micromalthidae Barber 1913, The telephone-pole beetles

• Suborder: MYXOPHAGA Crowson 1955

• Lepiceridae Hinton 1936

• Microsporidae Crotch 1873, The minute bog beetles

• Hydroscaphidae LeConte 1874, The skiff beetles

• Torridincolidae Steffan 1964

• Suborder: ADEPHAGA Schellenberg 1806

• Rhysodidae Laporte 1840, The wrinkled bark beetles

• Carabidae Latreille 1802, The ground beetles

• Gyrinidae Latreille 1810, The whirligig beetles

• Haliplidae Aubé 1836, The crawling water beetles

• Trachypachidae C. G. Thomson 1857, The false ground beetles

• Noteridae C. G. Thomson 1860, The burrowing water beetles

• Amphizoidae LeConte 1853, The trout-stream beetles

• Hygrobiidae Régimbart 1878

• Dytiscidae Leach 1815, The predacious diving beetles

• Suborder: POLYPHAGA Emery 1886

• Series: STAPHYLINIFORMIA Lameere 1900

• Superfamily: HYDROPHILOIDEA Latreille 1802

• Hydrophilidae Latreille 1802, The water scavenger beetles

• Sphaeritidae Shuckard 1839, The false clown beetles

• Synteliidae Lewis 1882

• Histeridae Gyllenhal, The clown beetles

• Superfamily STAPHYLINOIDEA Latreille 1802

• Hydraenidae Mulsant 1844, The minute moss beetles

• Ptiliidae Erichson 1845, The feather-winged beetles

• Agyrtidae C. G. Thomson 1859, The primitive carrion beetles

• Leiodidae Fleming 1821, The round fungus beetles

• Scydmaenidae Leach 1815, The antlike stone beetles

• Silphidae Latreille 1807, The carrion beetles

• Staphylinidae Latreille 1802, The rove beetles

• Series: SCARABAEIFORMIA Crowson 1960

• Superfamily: SCARABAEOIDEA Latreille 1802

• Lucanidae Latreille 1804, The stag beetles

• Diphyllostomatidae Holloway 1972, The diphyllostomatid beetles

• Passalidae Leach 1815, The bess beetles

• Glaresidae Semenovrlan-Shanskii and Medvedev 1932, The glaresid beetles

• Trogidae MacLeay 1819, The skin beetles

• Pleocomidae LeConte 1861, The rain beetles

• Geotrupidae Latreille 1802, The earth-boring dung beetles

• Belohinidae Paulian 1959

• Ochodaeidae Mulsant and Rey 1871, The ochodaeid scarab beetles

• Hybosoridae Erichson 1847, The hybosorid scarab beetles

• Ceratocanthidae Cartwright and Gordon 1971, The ceratocanthid scarab beetles

• Glaphyridae MacLeay 1819, The glaphyrid scarab beetles

• Scarabaeidae Latreille 1802, The scarab beetles

• Series: ELATERIFORMIA Crowson 1960

• Podabrocephalidae Pic 1930

• Rhinorhipidae Lawrence 1988

• Superfamily: SCIRTOIDEA Fleming 1821

• Decliniidae Nikitsky et al. 1994

• Eucinetidae Lacordaire 1857, The plate-thigh beetles

• Clambidae Fischer 1821, The minute beetles

• Scirtidae Fleming 1821, The marsh beetles

• Superfamily: DASCILLOIDEA Guérin-Méneville 1843

• Dascillidae Guérin-Méneville 1843

• Rhipiceridae Latreille 1834, The cicada parasite beetles

• Superfamily: BUPRESTOIDEA Leach 1815

• Schizopodidae LeConte 1861, The schizopodid beetles

• Buprestidae Leach 1815, The metallic wood-boring beetles

• Superfamily: BYRRHOIDEA Latreille 1804

• Byrrhidae Latreille 1804, The pill beetles

• Elmidae Curtis 1830, The riffle beetles

• Dryopidae Billberg 1820, The long-toes beetles

• Lutrochidae Kasap and Crowson 1975, The robust marsh-loving beetles

• Limnichidae Erichson 1846, The minute marsh-loving beetles

• Heteroceridae MacLeay 1825, The variegated mod-loving beetles

• Psephenidae Lacordaire 1854, The water penny beetles

• Cneoglossidae Champion 1897

• Ptilodactylidae Laporte 1836, The toe-winged beetles

• Chelonariidae Blanchard 1845, The turtle beetles

• Eulichadidae Crowson 1973, The eulichadid beetles

• Callirhipidae Emden 1924, The cedar beetles

• Superfamily: ELATEROIDEA Leach 1815

• Artematopodidae Lacordaire 1857, The soft-bodied plant beetles

• Brachypsectridae Leconte and Horn 1883, The Texas beetles

• Cerophytidae Latreille 1834, The rare click beetles

• Eucnemidae Eschscholtz 1829, The false click beetles

• Throscidae Laporte 1840, The false metallic wood-boring beetles

• Elateridae Leach 1815, The click beetles

• Plastoceridae Crowson 1972

• Drilidae Blanchard 1845

• Omalisidae Lacordaire 1857

• Lycidae Laporte 1836, The net-winged beetles

• Telegeusidae Leng 1920, The long-lipped beetles

• Phengodidae LeConte 1861, The glowworm beetles

• Lampyridae Latreille 1817, The firefly beetles

• Omethidae LeConte 1861, The false firefly beetles

• Cantharidae Imhoff 1856, The soldier beetles

• Series: BOSTRICHIFORMIA Forbes 1926

• Jacobsoniidae Heller 1926, The Jacobson's beetles

• Superfamily: DERODONTOIDEA LeConte 1861

• Derodontidae LeConte 1861, The tooth-necked fungus beetles

• Superfamily BOSTRICHOIDEA Latreille 1802

• Nosodendridae Erichson 1846, The wounded-tree beetles

• Dermestidae Latreille 1804, The skin and larder beetles

• Bostrichidae Latreille 1802, The horned powder-post beetles

• Anobiidae Fleming 1821, The death-watch beetles

• Series: CUCUJIFORMIA Lameere 1938

• Superfamily: LYMEXYLOIDEA Fleming 1821

• Lymexylidae Fleming 1821, The ship-timber beetles

• Superfamily: CLEROIDEA Latreille 1802

• Phloiophilidae Kiesenwetter 1863

• Trogossitidae Latreille 1802, The bark-gnawing beetles

• Chaetosomatidae Crowson 1952

• Cleridae Latreille 1802, The checkered beetles

• Acanthocnemidae Crowson 1964

• Phycosecidae Crowson 1952

• Prionoceridae Lacordaire 1857

• Melyridae Leach 1815, The soft-winged flower beetles

• Superfamily: CUCUJOIDEA Latreille 1802

• Protocucujidae Crowson 1954

• Sphindidae Jacquelin du Val 1860, The dry-fungus beetles

• Brachypteridae Erichson 1845, The short-winged flower beetles

• Nitidulidae Latreille 1802, The sap-feeding beetles

• Smicripidae Horn 1879, The palmetto beetles

• Monotomidae Laporte 1840, The root-eating beetles

• Boganiidae Sen Gupta and Crowson 1966

• Helotidae Reitter 1876

• Phloeostichidae Reitter 1911

• Silvanidae Kirby 1837, The silvanid flat bark beetles

• Passandridae Erichson 1845, The parasitic flat bark beetles

• Cucujidae Latreille 1802, The flat bark beetles

• Laemophloeidae Ganglbauer 1899, The lined flat bark beetles

• Propalticidae Crowson 1952

• Phalacridae Leach 1815, The shining flower beetles

• Hobartiidae Sen Gupta and Crowson 1966

• Cavognathidae Sen Gupta and Crowson 1966

• Cryptophagidae Kirby 1837, The silken fungus beetles

• Lamingtoniidae Sen Gupta and Crowson 1969

• Languriidae Crotch 1873, The lizard beetles

• Erotylidae Latreille 1802, The pleasing fungus beetles

• Byturidae Jacquelin du Val 1858, The fruitworm beetles

• Biphyllidae LeConte 1861, The false skin beetles

• Bothrideridae Erichson 1845, The dry bark beetles

• Cerylonidae Billberg 1820, The minute bark beetles

• Alexiidae Imhoff 1856

• Discolomatidae Horn 1878

• Endomychidae Leach 1815, The handsome fungus beetles

• Coccinellidae Latreille 1807, The ladybird beetles

• Corylophidae LeConte 1852, The minute fungus beetles

• Latridiidae Erichson 1842, The minute brown scavenger beetles

• Superfamily: TENEBRIONOIDEA Latreille 1802

• Mycetophagidae Leach 1815, The hairy fungus beetles

• Archeocrypticidae Kaszab 1964, The archeocryptic beetles

• Pterogeniidae Crowson 1953

• Ciidae Leach 1819, The minute tree-fungus beetles

• Tetratomidae Billberg 1820, The polypore fungus beetles

• Melandryidae Leach 1815, The false darkling beetles

• Mordellidae Latreille 1802, The tumbling flower beetles

• Rhipiphoridae Gemminger and Harold 1870,

• The wedge-shaped beetles

• Colydiidae Erichson 1842, The cylindrical bark beetles

• Monommatidae Blanchard 1845, The opossum beetles

• Zopheridae Solier 1834, The ironclad beetles

• Ulodidae Pascoe 1869

• Perimylopidae St. George 1939

• Chalcodryidae Watt 1974

• Trachelostenidae Lacordaire 1859

• Tenebrionidae Latreille 1802, The darkling beetles

• Prostomidae C. G. Thomson 1859, The jugular-horned beetles

• Synchroidae Lacordaire 1859, The synchroa beetles

• Oedemeridae Latreille 1810, The pollen-feeding beetles

• Stenotrachelidae C. G. Thomson 1859, The false long-horned beetles

• Meloidae Gyllenhal 1810, The blister beetles

• Mycteridae Blanchard 1845, The palm and flower beetles

• Boridae C. G. Thomson 1859, The conifer bark beetles

• Trictenotomidae Blanchard 1845

• Pythidae Solier 1834, The dead log bark beetles

• Pyrochroidae Latreille 1807, The fire-colored beetles

• Salpingidae Leach 1815, The narrow-waisted bark beetles

• Anthicidae Latreille 1819, The antlike flower beetles

• Aderidae Winkler 1927, The antlike leaf beetles

• Scraptiidae Mulsant 1856, The false flower beetles

• Superfamily: CHRYOMELOIDEA Latreille 1802

• Cerambycidae Latreille 1802, The long-horned beetles

• Bruchidae Latreille 1802, the pea and bean weevils

• Megalopodidae Latreille 1802, The megalopodid leaf beetles

• Orsodacnidae C. G. Thomson 1859, The orsodacnid leaf beetles

• Chrysomelidae Latreille 1802, The leaf beetles

• Superfamily: CURCULIONOIDEA Latreille 1802

• Nemonychidae Bedel 1882, The pine-flower snout beetles

• Anthribidae Billberg 1820, The fungus weevils

• Belidae Schönherr 1826, The primitive weevils

• Attelabidae Billberg 1820, The tooth-nosed snout beetles

• Brentidae Billberg 1820, The straight-snouted weevils

• Caridae Thompson 1992

• Ithyceridae Schönherr 1823, The New York weevils

• Curculionidae Latreille 1802, The snout beetles and true weevils

See also, BARK BEETLES, BESS BEETLES, BLISTER BEETLES, DARKLING BEETLES, FIREFLIES, GROUND BEETLES, JUNE BEETLES, LEAF BEETLES, LONGICORN BEETLES, POWDERPOST BEETLES, RIFFLE BEETLES, ROVE BEETLES, SAP BEETLES, WATER PENNY BEETLES