Arachnis (plant)

The genus Arachnis, abbreviated as Arach in horticultural trade, (common name scorpion orchid,^[2][3]) 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.^[4][5]

Arachnis
Inflorescence detail of Arachnis longisepala
Flowering Arachnis labrosa specimen
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Monocots
Order:	Asparagales
Family:	Orchidaceae
Subfamily:	Epidendroideae
Tribe:	Vandeae
Subtribe:	Aeridinae
Genus:	Arachnis Blume
Type species
Arachnis flos-aeris (L.) Rchb.f.
Synonyms[1]
Arachnanthe Blume Arhynchium Lindl. Armodorum Breda Esmeralda Rchb.f.

Description

Vegetative characteristics

The appearance of the monopodial, epiphytic herbs of the genus Arachnis is characterized by distichously arranged, linear leaves.^[6] The vining plants may grow into a dense thicket.^[7] Arachnis does not produce pseudobulbs.^[8]

Generative characteristics

The flowers are thought to resemble spiders,^[8] and they are fragrant.^[6][8] The fragrance has been described as musky.^[8]

• 
  Arachnis labrosa growing epiphytically on a tree
• 
  Detail of Arachnis labrosa flower
• 
  Botanical illustration of Arachnis clarkei
• 
  Detail of Arachnis cathcartii flower
• 
  Detail of Arachnis flos-aeris flower
• 
  Botanical illustration of Arachnis annamensis

Etymology

The generic epithet Arachnis is derived from the Greek word arachne for spider.^[9]

Ecology

Habitat

Arachnis senapatiana has been found growing in subtropical broad-leaved forests at elevations of 1747 m above sea level.^[6]

Flowering

Arachnis senapatiana is known to flower in June.^[6]

Taxonomy

Accepted species

There are currently 16 accepted species, including one natural hybrid:^[1]

• 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.^[10]
• Arachnis breviscapa (J.J.Sm.) J.J.Sm. is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit.^[11]
• Arachnis celebica (Schltr.) J.J.Sm. is now considered to be Dimorphorchis celebica (Schltr.) Ormerod^[12]
• Arachnis imthurnii (Rolfe) L.O.Williams is now considered to be Dimorphorchis beccarii var. imthurnii (Rolfe) Kocyan & Schuit.^[13]
• Arachnis longicaulis (Schltr.) L.O.Williams is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit.^[11]
• Arachnis lowii (Lindl.) Rchb.f. is now considered to be Dimorphorchis lowii (Lindl.) Rolfe^[14]
• Arachnis lyonii Ames is now considered to be Dimorphorchis lyonii (Ames) Ormerod^[15]
• Arachnis muelleri (Kraenzl.) J.J.Sm. is now considered to be Dimorphorchis beccarii var. beccarii^[16]
• Arachnis philippinensis (Lindl.) Ames is now considered to be Trichoglottis philippinensis Lindl.^[17]
• Arachnis rohaniana (Rchb.f.) Rchb.f. is now considered to be Dimorphorchis rohaniana (Rchb.f.) P.J.Cribb^[18]
• Arachnis beccarii var. imthurnii (Rolfe) K.W.Tan is now considered to be Dimorphorchis beccarii var. imthurnii (Rolfe) Kocyan & Schuit.^[19]
• Arachnis longicaulis f. flavescens Valmayor & D.Tiu is now considered to be Dimorphorchis breviscapa (J.J.Sm.) Kocyan & Schuit.^[11]

Conservation

Arachnis has become extinct in Nansei-shoto.^[1]

Horticulture

It can be cultivated under warm and moist conditions growing in pots, baskets, or mounted on slabs.^[7]