The genus Arachnis, abbreviated as Arach in horticultural trade, (common name scorpion orchid,) is a member of the orchid family (Orchidaceae), consisting of more than 20 species native to China, India, Southeast Asia, Indonesia, the Philippines, New Guinea, and the Solomon Islands.Kew World Checklist of Selected Plant FamiliesFlora of China, v25 p 465, 蜘蛛兰属 zhi zhu lan shu, Arachnis
Description Vegetative characteristics The appearance of the monopodial, epiphytic herbs of the genus Arachnis is characterized by distichously arranged, linear leaves. The vining plants may grow into a dense thicket. Arachnis does not produce pseudobulbs.Tan, K. W. (1974). "Taxonomy of Arachnis, Armodorum, Esmeralda and Dimorphorchis (Orchidaceae)." University of Miami.
Generative characteristics The flowers are thought to resemble spiders, and they are fragrant. The fragrance has been described as musky.
Etymology The generic epithet Arachnis is derived from the Greek word arachne for spider.Teoh, E.S. (2021). Arachnis Bl.. In: Orchid Species from Himalaya and Southeast Asia Vol. 1 (A - E). Springer, Cham. https://doi.org/10.1007/978-3-030-58872-4_15
Ecology Habitat Arachnis senapatiana has been found growing in subtropical broad-leaved forests at elevations of 1747 m above sea level.Jakha, H. Y., Deb, C. R., Dey, S., & Jamir, N. S. (2014). "Arachnis senapatiana (Phukan & AA Mao) Kocyan & Schuiteman (Orchidaceae): an addition to the flora of Nagaland, India." Pleione, 8(2), 516-518.
Flowering Arachnis senapatiana is known to flower in June.
Taxonomy Accepted species There are currently 16 accepted species, including one natural hybrid: Arachnis annamensis (Rolfe) J.J.Sm. Arachnis bella (Rchb.f.) J.J.Sm. Arachnis bouffordii Ormerod Arachnis calcarata Holttum Arachnis cathcartii (Lindl.) J.J.Sm. Arachnis clarkei (Rchb.f.) J.J.Sm. Arachnis flos-aeris (L.) Rchb.f. Arachnis grandisepala J.J.Wood Arachnis hookeriana (Rchb.f.) Rchb.f. Arachnis labrosa (Lindl. & Paxton) Rchb.f. Arachnis limax Seidenf. Arachnis longisepala (J.J.Wood) Shim & A.Lamb Arachnis × maingayi (Hook.f.) Schltr. Arachnis senapatiana (Phukan & A.A.Mao) Kocyan & Schuit. Arachnis seramensis (Ormerod) R.Rice Arachnis siamensis (Schltr.) Tang & F.T.Wang Arachnis sulingi (Blume) Rchb.f.
Species formerly placed in Arachnis Arachnis beccarii Rchb.f. is now considered to be Dimorphorchis beccarii (Rchb.f.) Kocyan & Schuit. Arachnis breviscapa (J.J.Sm.) J.J.Sm. is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit. Arachnis celebica (Schltr.) J.J.Sm. is now considered to be Dimorphorchis celebica (Schltr.) Ormerod Arachnis imthurnii (Rolfe) L.O.Williams is now considered to be Dimorphorchis beccarii var. imthurnii (Rolfe) Kocyan & Schuit. Arachnis longicaulis (Schltr.) L.O.Williams is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit. Arachnis lowii (Lindl.) Rchb.f. is now considered to be Dimorphorchis lowii (Lindl.) Rolfe Arachnis lyonii Ames is now considered to be Dimorphorchis lyonii (Ames) Ormerod Arachnis muelleri (Kraenzl.) J.J.Sm. is now considered to be Dimorphorchis beccarii var. beccarii Arachnis philippinensis (Lindl.) Ames is now considered to be Trichoglottis philippinensis Lindl. Arachnis rohaniana (Rchb.f.) Rchb.f. is now considered to be Dimorphorchis rohaniana (Rchb.f.) P.J.Cribb Arachnis beccarii var. imthurnii (Rolfe) K.W.Tan is now considered to be Dimorphorchis beccarii var. imthurnii (Rolfe) Kocyan & Schuit. Arachnis longicaulis f. flavescens Valmayor & D.Tiu is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit.
Conservation Arachnis has become extinct in Nansei-shoto.
Horticulture It can be cultivated under warm and moist conditions growing in pots, baskets, or mounted on slabs.Rach, N. (n.d.). Arachnis Blume 1825. American Orchid Society. Retrieved January 6, 2023, from https://www.aos.org/orchids/orchids-a-to-z/letter-a/arachnis.aspx
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