Editing Beetle (section)

==External morphology==
[[File:Melolontha_melolontha_insect_morphology.jpg|300px|thumb|right|Beetle body structure, using [[cockchafer]].
A: head, B: thorax, C: abdomen.
1: antenna, 2: compound eye, 3: femur, 4: elytron (wing cover), 5: tibia, 6: tarsus, 7: claws, 8: mouthparts, 9: prothorax, 10: mesothorax, 11: metathorax, 12: abdominal sternites, 13: pygidium.]]

Beetles are generally characterized by a particularly hard [[exoskeleton]] and hard forewings ([[elytra]]) not usable for flying. Almost all beetles have mandibles that move in a horizontal plane. The mouthparts are rarely suctorial, though they are sometimes reduced; the maxillae always bear palps. The antennae usually have 11 or fewer segments, except in some groups like the Cerambycidae (longhorn beetles) and the Rhipiceridae (cicada parasite beetles). The coxae of the legs are usually located recessed within a coxal cavity. The genitalic structures are telescoped into the last abdominal segment in all extant beetles. Beetle larvae can often be confused with those of other holometabolan groups.<ref name="ausbeetle">{{cite book |title=Australian Beetles. Morphology, Classification and Keys |year=2013 |last2=Ślipiński |first2=Adam |publisher=CSIRO |isbn=978-0-643-09728-5 |first1=John F. |last1=Lawrence |pages=1–16}}</ref> The beetle's exoskeleton is made up of numerous plates, called [[sclerite]]s, separated by thin sutures. This design provides armored defenses while maintaining flexibility. The general [[anatomy]] of a beetle is quite uniform, although specific organs and [[appendage]]s vary greatly in appearance and function between the many families in the order. Like all insects, beetles' bodies are divided into three sections: the head, the thorax, and the abdomen.<ref name=insenc/> Because there are so many species, identification is quite difficult, and relies on attributes including the shape of the antennae, the [[tarsal formula]]e{{efn|These count fore, mid, and hind leg tarsal segments, such as 5-5-4.}} and shapes of these small segments on the legs, the mouthparts, and the ventral plates (sterna, pleura, coxae). In many species accurate identification can only be made by examination of the unique male genitalic structures.<ref>{{cite web| title=Introduction to the Identification of Beetles (Coleoptera)| url = http://entnemdept.ufl.edu/choate/beetles.pdf |publisher=University of Florida| access-date=15 March 2017}}</ref>

===Head===
[[File:Head of the Weaver Beetle (Lamia textor).jpg|left|thumb|Front view of the head of ''[[Lamia textor]]'']]

The head, having mouthparts projecting forward or sometimes downturned, is usually heavily [[Sclerotin|sclerotized]] and is sometimes very large.<ref name="Gilliott"/> The eyes are [[compound eye|compound]] and may display remarkable adaptability, as in the case of the aquatic whirligig beetles ([[Gyrinidae]]), where they are split to allow a view both above and below the waterline. A few [[Longhorn beetle]]s ([[Cerambycidae]]) and weevils as well as some fireflies ([[Rhagophthalmidae]]) <ref name="Lau">{{ cite journal|author1=Lau T.F.S.| author2=Meyer-Rochow V.B.| title=Sexual dimorphism in the compound eye of ''Rhagophthalmus ohbai'' (Coleoptera; Rhagophthalmidae): I. Morphology and ultrastructure| date=2006| journal= Journal of Asia-Pacific Entomology| volume=9| pages=19–30| doi=10.1016/S1226-8615(08)60271-X}}</ref> have divided eyes, while many have eyes that are notched, and a few have [[ocelli]], small, simple [[eye]]s usually farther back on the head (on the [[Vertex (anatomy)|vertex]]); these are more common in larvae than in adults.<ref name='BeetlesAustralia'>{{cite book |author1=Hangay, G. |author2=Zborowski, P.|title=A Guide to the Beetles of Australia |url=https://archive.org/details/guidetobeetlesau00hang |url-access=limited |date=2010 |publisher=CSIRO |page=[https://archive.org/details/guidetobeetlesau00hang/page/n245 10]|isbn=978-0-643-09487-1}}</ref> The anatomical organization of the compound eyes may be modified and depends on whether a species is primarily crepuscular, or diurnally or nocturnally active.<ref name='beetles'>{{cite journal| author1= Gokan N.| author2= Meyer-Rochow V.B.|title=Morphological comparisons of compound eyes in Scarabaeoidea (Coleoptera) related to the beetles' daily activity maxima and phylogenetic positions| date=2000|journal=Journal of Agricultural Science (Tokyo Nogyo Daigaku)| volume=45| issue= 1|pages= 15–61}}</ref> Ocelli are found in the adult carpet beetle (as a single central ocellus in [[Dermestidae]]), some rove beetles ([[Omaliinae]]), and the [[Derodontidae]].<ref name='BeetlesAustralia'/>

[[File:Polyphylla fullo up.jpg|thumb|''[[Polyphylla fullo]]'' has distinctive fan-like [[antenna (biology)|antennae]], one of several distinct forms for the appendages among beetles.|left]]

Beetle [[antenna (biology)|antennae]] are primarily organs of sensory perception and can detect motion, odor and chemical substances,<ref name='Antennae'>{{cite web |url=http://www.kerbtier.de/Pages/Themenseiten/enKoerperbau.html#Fuehler |title=3. Antennae, Beetle morphology |last1=Benisch |first1=Christoph |date=2007 |publisher=Kerbtier.de (Beetle fauna of Germany) |access-date=2017-03-14}}</ref> but may also be used to physically feel a beetle's environment. Beetle families may use antennae in different ways. For example, when moving quickly, tiger beetles may not be able to see very well and instead hold their antennae rigidly in front of them in order to avoid obstacles.<ref>{{cite journal |doi=10.1098/rspb.2013.3072 |pmid=24500171 |title=Static antennae act as locomotory guides that compensate for visual motion blur in a diurnal, keen-eyed predator |journal=Proceedings of the Royal Society B: Biological Sciences |volume=281 |issue=1779 |page=20133072 |year=2014 |last1=Zurek |first1=D.B. |last2=Gilbert |first2=C. |pmc=3924084 }}</ref>
Certain Cerambycidae use antennae to balance, and blister beetles may use them for grasping. Some aquatic beetle species may use antennae for gathering air and passing it under the body whilst submerged. Equally, some families use antennae during mating, and a few species use them for defense. In the cerambycid ''[[Onychocerus albitarsis]]'', the antennae have venom injecting structures used in defense, which is unique among [[arthropod]]s.<ref>{{cite journal|doi=10.1007/s00114-007-0316-1|pmid=18004534|title=Convergent evolution in the antennae of a cerambycid beetle, ''Onychocerus albitarsis'', and the sting of a scorpion|journal=Naturwissenschaften|volume=95|issue=3|pages=257–61|year=2007|last1=Berkov|first1=Amy|last2=Rodríguez|first2=Nelson|last3=Centeno|first3=Pedro|bibcode=2008NW.....95..257B|s2cid=30226487}}</ref> Antennae vary greatly in form, sometimes between the sexes, but are often similar within any given family. Antennae may be [[wikt:clavate|clubbed]], [[wikt:filiform|threadlike]], [[wikt:geniculate|angled]], [[wikt:moniliform|shaped like a string of beads]], [[wikt:pectinate|comb-like]] (either on one side or both, bipectinate), or [[wikt:serrate|toothed]]. The physical variation of antennae is important for the identification of many beetle groups. The Curculionidae have elbowed or geniculate antennae. Feather like flabellate antennae are a restricted form found in the Rhipiceridae and a few other families. The Silphidae have a capitate antennae with a spherical head at the tip. The Scarabaeidae typically have lamellate antennae with the terminal segments extended into long flat structures stacked together. The Carabidae typically have thread-like antennae. The antennae arises between the eye and the mandibles and in the Tenebrionidae, the antennae rise in front of a notch that breaks the usually circular outline of the compound eye. They are segmented and usually consist of 11 parts, the first part is called the scape and the second part is the pedicel. The other segments are jointly called the flagellum.<ref name='Antennae'/><ref>{{cite web |url=http://bugs.bio.usyd.edu.au/learning/resources/Entomology/externalMorphology/antennaTypes.html |title=Antennae Types |publisher=University of Sydney |access-date=2017-01-26 |archive-date=February 22, 2018 |archive-url=https://web.archive.org/web/20180222221339/http://bugs.bio.usyd.edu.au/learning/resources/Entomology/externalMorphology/antennaTypes.html  }}</ref><ref>{{cite book |title=American Beetles, Volume I: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia |author1= Arnett, R. H. Jr.|author2=Thomas, M. C. |date=2001 |publisher=CRC Press |isbn=978-1-4822-7432-5 |pages=3–7}}</ref>

Beetles have [[Insect mouthparts|mouthparts]] like those of [[grasshopper]]s. The [[mandible (insect)|mandibles]] 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 [[#Anti-predator adaptations|defence]], below). Two pairs of finger-like appendages, the maxillary and labial palpi, are found around the mouth in most beetles, serving to move food into the mouth. In many species, the mandibles are sexually dimorphic, with those of the males enlarged enormously compared with those of females of the same species.<ref name="Gilliott"/>

===Thorax===
The thorax is [[segmentation (biology)|segmented]] into the two discernible parts, the pro- and pterothorax. The pterothorax is the fused meso- and metathorax, which are commonly separated in other insect species, although flexibly articulate from the prothorax. When viewed from below, the thorax is that part from which all three pairs of legs and both pairs of wings arise. The abdomen is everything posterior to the thorax.<ref name=insenc/> When viewed from above, most beetles appear to have three clear sections, but this is deceptive: on the beetle's upper surface, the middle section is a hard plate called the [[pronotum]], which is only the front part of the thorax; the back part of the thorax is concealed by the beetle's [[insect wing|wings]]. This further segmentation is usually best seen on the abdomen.{{Citation needed|date=June 2023}}<ref>Kusinitz, M. (2021). Beetles. In K. H. Nemeh & J. L. Longe (Eds.), ''The Gale Encyclopedia of Science'' (6th ed., Vol. 1). Gale. 531-536. Gale Document Number: CX8124400293</ref>

[[File:Acilius sulcatus.gemeiner furchenschwimmer.jpg|thumb|''[[Acilius sulcatus]]'', a diving beetle with hind legs adapted as [[Animal locomotion#Swimming|swimming]] limbs]]

===Legs===
The multisegmented [[arthropod leg|legs]] end in two to five small segments called tarsi. Like many other insect orders, beetles have claws, usually one pair, on the end of the last tarsal segment of each leg. While most beetles use their legs for walking, legs have been variously adapted for other uses. Aquatic beetles including the [[Dytiscidae|Dytiscidae (diving beetles)]], [[Haliplidae]], and many species of [[Hydrophilidae]], the legs, often the last pair, are modified for swimming, typically with rows of long hairs. Male diving beetles have suctorial cups on their forelegs that they use to grasp females.<ref>{{Cite journal |last1=Green |first1=Kristina Karlsson |last2=Kovalev |first2=Alexander |last3=Svensson |first3=Erik I. |last4=Gorb |first4=Stanislav N. |date=2013 |title=Male clasping ability, female polymorphism and sexual conflict: fine-scale elytral morphology as a sexually antagonistic adaptation in female diving beetles |journal=Journal of the Royal Society Interface |volume=10 |issue=86 |page=20130409 |doi=10.1098/rsif.2013.0409 |pmc=3730688 |pmid=23825114}}</ref> Other beetles have [[fossorial]] legs widened and often spined for digging. Species with such adaptations are found among the scarabs, ground beetles, and [[clown beetle]]s ([[Histeridae]]). The hind legs of some beetles, such as [[flea beetle]]s (within Chrysomelidae) and flea weevils (within Curculionidae), have enlarged femurs that help them leap.<ref>{{cite web |author1=Burkness, S. |author2=Hahn, J. |date=2007 |title=Flea beetles in home gardens |url=http://www.extension.umn.edu/garden/insects/find/flea-beetles/ |access-date=2017-01-26 |publisher=[[University of Minnesota Extension]]}}</ref>

===Wings===
[[File: Soldier Beetle Trichodes alvearius taking off from Knapweed (cropped).jpg|thumb|Checkered beetle ''[[Trichodes alvearius]]'' taking off, showing the hard elytra (forewings adapted as wing-cases) held stiffly away from the flight wings|left]]

The forewings of beetles are not used for [[insect flight|flight]], but form elytra which cover the hind part of the body and protect the hindwings. The elytra are usually hard shell-like structures which must be raised to allow the hindwings to move for flight.<ref name="Carpenter"/> However, in the soldier beetles ([[Cantharidae]]), the elytra are soft, earning this family the name of leatherwings.<ref>{{Citation |title=Leatherwing (Soldier) Beetles |author1=Philips, Chris |author2=Fread, Elizabeth |author3=Kuhar, Tom |access-date=14 March 2017 |url=http://pubs.ext.vt.edu/ENTO/ENTO-53/ENTO-53-pdf.pdf |archive-url=https://web.archive.org/web/20161130002157/http://www.pubs.ext.vt.edu/ENTO/ENTO-53/ENTO-53-pdf.pdf |archive-date=November 30, 2016  }}</ref> Other soft wing beetles include the [[net-winged beetle]] ''[[Calopteron discrepans]]'', which has brittle wings that rupture easily in order to release chemicals for defense.<ref>{{cite web |url=http://entomology.ifas.ufl.edu/creatures/misc/beetles/banded_net-winged_beetle.htm |title=Calopteron discrepans (Newman) (Insecta: Coleoptera: Lycidae) |author1=Donald W. Hall |author2=Marc A. Branham |date=2016 |publisher=[[University of Florida]] |access-date=2017-03-15}}</ref>

Beetles' flight wings are crossed with veins and are folded after landing, often along these veins, and stored below the elytra. A fold (''jugum'') of the membrane at the base of each wing is characteristic.<ref name="Carpenter">{{cite book |title=Insects, their structure and life |first=George Herbert |last=Carpenter |year=1899}}</ref> Some beetles have lost the ability to fly. These include some ground beetles (Carabidae) and some true weevils (Curculionidae), as well as desert- and cave-dwelling species of other families. Many 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, as in the [[glow-worm]]s ([[Phengodidae]]), where the females [[Larviform female|resemble larvae]] throughout their lives.<ref>{{cite web |url=http://delta-intkey.com/elateria/www/phenmplf.htm |title=''Elateriformia'' (Coleoptera): descriptions, illustrations, identification, and information retrieval for families and subfamilies |author1=Lawrence, J. F. |author2=Hastings, A. M. |author3=Dallwitz, M. J. |author4=Paine, T. A. |author5=Zurcher, E. J. |date=2005 |access-date=2017-01-26}}</ref> The presence of elytra and wings does not always indicate that the beetle will fly. For example, the [[tansy beetle]] walks between habitats despite being physically capable of flight.<ref>{{cite journal |author1=Beenen, R |author2=Winkelman, J. K. |date=2001 |title=Aantekeningen over Chrysomelidae in Nederland 5 |journal=Entomologische Berichten |language=nl |volume=61 |pages=63–67}}</ref>

===Abdomen===
The [[Abdomen#Arthropoda|abdomen]] is the section behind the metathorax, made up of a series of rings, each with a hole for breathing and respiration, called a [[Spiracle (arthropods)|spiracle]], composing three different segmented sclerites: the tergum, pleura, and the sternum. The tergum in almost all species is membranous, or usually soft and concealed by the wings and elytra when not in flight. The pleura are usually small or hidden in some species, with each pleuron having a single spiracle. The sternum is the most widely visible part of the abdomen, being a more or less sclerotized segment. The abdomen itself does not have any appendages, but some (for example, [[Mordellidae]]) have articulating sternal lobes.<ref name="American">{{cite book |last1=Arnett|first1=Ross H. Jr |last2=Thomas |first2=Michael C. |title=American Beetles, Volume I: Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia |url=https://books.google.com/books?id=bJjSBQAAQBAJ&pg=PA8 |year=2000 |publisher=CRC Press |isbn=978-1-4822-7432-5 |page=8}}</ref>