Arthrochilus

{{Short description|Genus of flowering plants}} {{Use Australian English|date=July 2024}} {{Italic title}} {{automatic taxobox | name = Elbow orchids | image = Arthrochilus latipes (4437242906).jpg | image_caption = ''[[Arthrochilus latipes]]'' in [[Kakadu National Park]] | display_parents = 3 | taxon = Arthrochilus | authority = [[F.Muell.]]<ref name="PoWO">{{cite web |title=''Arthrochilus'' |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:28769-1 |publisher=Plants of the World Online |access-date=23 October 2025}}</ref> | type_species = | type_species_authority = | synonyms_ref = <ref name="PoWO" /> | synonyms = *''Phoringopsis'' [[D.L.Jones]] & [[M.A.Clem.]] *''Thynninorchis'' D.L.Jones & M.A.Clem. }}

'''''Arthrochilus''''', commonly called '''elbow orchids,''' is a [[genus]] of about fifteen species of [[flowering plant]]s from the [[orchid]] family (Orchidaceae) and is found in [[Australia]] and [[New Guinea]]. The flowers are pollinated by male [[Thynnidae|thynnid wasps]] which attempt to mate with the flower and are held in place by hooks while the [[pollinium]] is transferred between insect and flower.

==Description== Orchids in the genus ''Arthrochilus'' are terrestrial, [[Perennial plant|perennial]], [[deciduous]], [[sympodial]] [[Herbaceous plant|herbs]] usually with a few inconspicuous, fine roots and a single oval-shaped [[tuber]] lacking a protective fibrous [[Tunica (biology)|sheath]]. (''[[Arthrochilus huntianus|A. huntianus]]'' lacks a true tuber.) Some species form colonies, reproducing asexually from daughter tubers formed on the end of root-like [[stolon]]s. The stem is short, erect and unbranched with thin, leaf-like [[cataphyll]]s at each [[Plant stem|node]]. There are up to six leaves at or near the base of the plant, sometimes forming a [[Rosette (botany)|rosette]] around the stem.<ref name="Orchids">{{cite book|editor-last1=Pridgeon |editor-first1=Alec M.|editor-last2=Cribb |editor-first2=Phillip J.|editor-last3=Chase |editor-first3=Mark W.|editor-last4=Rasmussen |editor-first4=Finn|title=Genera Orchidacearum, Volume 2, Orchidoideae (part 1)|date=2001|publisher=Oxford University Press|location=Oxford, England|isbn=0198507100|pages=135–139}}</ref><ref name="RBGS">{{cite web|last1=Bernhardt|first1=Peter H.|title=Genus ''Arthrochilus''|url=http://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&showsyn=&dist=&constat=&lvl=gn&name=Arthrochilus|publisher=Royal Botanic Garden Sydney: plantnet|accessdate=22 July 2016}}</ref><ref name="ATROK">{{cite web |author1=D.L.Jones |author2=T.Hopley |author3=S.M.Duffy |author1-link=David L. Jones (botanist) |year=2010 |access-date=27 May 2021 |url=https://www.canbr.gov.au/cpbr/cd-keys/RFKOrchids/key/rfkorchids/Media/Html/genera/Arthrochilus.htm |title=Arthrochilus |website=[[Australian Tropical Rainforest Orchids]] |publisher=Centre for Australian National Biodiversity Research (CANBR), [[Australian Government]]}}</ref>[[File:Arthrochilus (correct labels).001.jpg|thumb|225px|Labelled image]]

The [[inflorescence]] is a [[raceme]] with a few to many non-[[Resupination#Orchidaceae|resupinate]], dull-coloured flowers on a wiry stalk. The [[wikt:dorsal|dorsal]] [[sepal]] is similar to or larger than the [[wikt:lateral|lateral]] sepals and its sides curve inwards. The lateral sepals and [[petal]]s are attached the base of the [[Column (botany)|column]], the petals similar to, but smaller than the sepals. The highly modified [[Labellum (botany)|labellum]] is dominated by the [[Labellum (botany)|callus]] and is hinged to the column by a flexible "claw". The callus is ornamented with feathery [[Cilium|cilia]] and club-shaped structures which gives the labellum the form of a wingless, female wasp. The column has two pairs of wings, two which surround the sexual parts of the flower and two larger hook-like wings either side of the column. Elbow orchids mainly flower in summer and the fruit that follows flowering is a [[wikt:glabrous|glabrous]] [[Dehiscence (botany)|dehiscent]] [[Capsule (botany)|capsule]] containing a large number of winged seeds.<ref name="Orchids" /><ref name="RBGS" /><ref name="ATROK" />

==Taxonomy and naming== The genus ''Arthrochilus'' was first formally described in 1858 by [[Ferdinand von Mueller]] and the description was published in ''[[Fragmenta phytographiae Australiae]]''. Mueller described ''[[Arthrochilus irritabilis]]'' at the same time and it is regarded as the [[type species]].<ref name=APNI>{{cite web|title=''Arthrochilus''|url= https://id.biodiversity.org.au/instance/apni/530064|publisher=APNI|accessdate=22 July 2016}}</ref><ref name="F.Muell.">{{cite book|last1=von Mueller|first1=Ferdinand|title=Fragmenta phytographiae Australiae (Volume 1)|date=1858|location=London|pages=42–43|url=https://www.biodiversitylibrary.org/item/7218#page/44/mode/1up|accessdate=22 July 2016}}</ref> The scientific name of the genus is derived from the [[Ancient Greek]] words ''arthron'' meaning "joint"<ref name="RWB">{{cite book|last1=Brown|first1=Roland Wilbur|title=The Composition of Scientific Words|date=1956|publisher=Smithsonian Institution Press|location=Washington, D.C.}}</ref>{{rp|446}} and ''cheilos'' meaning "lip"<ref name="RWB" />{{rp|200}} referring to the jointed labellum.<ref name="Orchids" />

==Distribution and habitat== Elbow orchids are found in all states of Australia except [[Western Australia]] and in southern [[Papua New Guinea]] and on the [[Torres Strait Islands]]. The majority of elbow orchid species occur in tropical regions but ''[[Arthrochilus huntianus|A. huntianus]]'' grows in eastern Australia with the subspecies ''nothofagicola'' occurring in [[Tasmania]]. The tropical species grow and flower in the summer wet season, usually growing in sand in forest or woodland.<ref name="Orchids" />

==Ecology== The labellum of elbow orchids mimics wingless female thynnid wasps of the [[Taxonomic rank|Superfamily]] [[Vespoidea]], [[Family (taxonomy)|Family]] [[Thynnidae]]. In its attempt to fly off with the dummy female, the insect is thrust head-first against the column where the hooked wings hold the insect in place long enough for the [[Pollinium|pollinia]] to stick to its back. If it is carrying pollinia from another flower, the pollinia are crushed against the [[Stigma (botany)|stigma]]. For three species of elbow orchid, a single species of wasp from the genus ''[[Arthrothynnus]]'' has been identified. In the case of some tropical species, the wasps struggle so violently with the labellum that the organ is often torn off. Some other orchids similarly employ thynnid wasps as pollinators but only ''Arthrochilus'' flowers have restraining hooks on the labellum.<ref name="Orchids" /><ref name="Pridgeon">{{cite book|editor-last1=Pridgeon|editor-first1=Alec M. |title=Genera Orchidacearum. Volume 2, Orchidoideae (part 1)|date=2001|publisher=Oxford University Press|location=Oxford, England|isbn=0198507100|pages=137–138}}</ref>

==Species list== The following is a list of species recognised by the ''[[Plants of the World Online]]'' as at October 2025:<ref name="PoWO" /> {{div col|colwidth=35em}} *''[[Arthrochilus apectus]]'' D.L.Jones - untidy elbow orchid ([[Queensland|Qld.]]) *''[[Arthrochilus aquilus]]'' D.L.Jones - dark elbow orchid (Qld.) *''[[Arthrochilus byrnesii]]'' Blaxell - sandstone truffle orchid (N.T., W.A.) *''[[Arthrochilus corinnae]]'' D.L.Jones - swamp elbow orchid (Qld.) *''[[Arthrochilus dockrillii]]'' Lavarack - green truffle orchid (Qld.) *''[[Arthrochilus huntianus]]'' (F.Muell.) Blaxell - common elbow orchid (N.S.W., Tas., Vic., S.A.) *''[[Arthrochilus irritabilis]]'' F.Muell. - clubbed elbow orchid (Qld.) *''[[Arthrochilus laevicallus]]'' Ormerod (Papua New Guinea) *''[[Arthrochilus latipes]]'' D.L.Jones - robust elbow orchid (N.T.) *''[[Arthrochilus lavarackianus]]'' (D.L.Jones) Lavarack - glaucous truffle orchid (Qld.) *''[[Arthrochilus oreophilus]]'' D.L.Jones - montane elbow orchid (Qld.) *''[[Arthrochilus prolixus]]'' D.L.Jones - wispy elbow orchid (N.S.W., Qld.) *''[[Arthrochilus rosulatus]]'' D.L.Jones - rosetted elbow orchid (Qld.) *''[[Arthrochilus sabulosus]]'' D.L.Jones - spotted elbow orchid (Qld.) *''[[Arthrochilus stenophyllus]]'' D.L.Jones - narrow-leaved elbow orchid (Qld.) {{div col end}}

== See also == * [[List of Orchidaceae genera]]

== References == {{Reflist}}

== External links == {{Commons}} * [http://www.ourshopfront.com/kabi/html/Natives/Arthrochilus%20prolixus.php Australian Native Orchid Society (Queensland), Kabi Group, ''Arthrochilus prolixus''] * [http://www.retiredaussies.com/ColinsHome%20Page/Orchids/Thynninorchis/Thynninorchis%20huntianus.htm Retired Aussies, ''Thynninorchis huntianus'', Elbow Orchid, synonym ''Arthrochilus huntianus''] * [https://web.archive.org/web/20140521200422/http://www.orchidsonline.com.au/node/2409 Orchids Online, ''Arthrochilus oreophilus'', Synonym: ''Spiculea irritabilis'' sensu Dockr.]

[[Category:Arthrochilus| ]] [[Category:Diurideae genera]] [[Category:Orchids of Australia]] [[Category:Flora of Queensland]] [[Category:Orchids of New Guinea]]