Arachnis Blume
in Bijdragen tot de Flora van Nederlandsch Indie; 1825, 565

Introduction: About twenty species of these epiphytic or lithophytic orchids can be found from Burma, Thailand, Malaya through Indonesia to New Guinea. Species of the genus Arachnis have frequently been used in hybridizing. Most species in the genus can be crossed with species of the genus Vanda. Their offspring are then combined in a new genus called Aranda.

Derivation of genus name: The Greek arachne (spider) perfectly describes the appearance of the flowers of this genus.

Type species: A. moschifera Bl. (=A. flosaeris (L) Reichb.f.)

Characteristics of genus:Plants large, often climbing monopodials, stems long, leafy. Leaves in two rows, spaced well apart, oblong or tapering towards the tip, apices bilobed. Inflorescence short or long, erect or pendulous simple or branched, with few to many large flowers. Flowers spreading, with large sepals and petals and a small hinged lip. labellum isattached to a short massive column foot, fleshy, trilobed with a very short spur; lateral lobes broad, usually retangular, midlobe fleshy, with a median keel and in some species with a fleshy chin-like callus below the tip. Column short and thick, with a short foot. Pollinia 4, almost equal an in 2 pairs, on a short broad stipe with a large viscidium.

Number of sections and/or subsections in genus: There appear to be three sections. The first to which A. flosaeries from SE Asia is representative; the second contains those species with short unbranched inflorescences such as the New Guinea A. longicaulis and A. breviscarpa a close relative from Borneo; the third is represented by A. beccarii which is a stocky, robust species, with very long, fleshy, tapering, strap-shaped leaves and a tall, erect, many branched inflorescence.

Number of species in New Guinea: two, possibly three

A. beccarii (Rchb. f. )J.J.Sm. syn. A. muelleri (Krzl.) J.J. Sm.
A. longicaulis Schltr.

View photo: Arachnis beccarii

Species shown here: Arachnis beccarii (Reichb. f.) J.J.Sm.

Habitat: Arachnis muelleri (Krzl.) J.J. Smith can be found at the Rouna Falls in the Central Province where it grows on rocks exposed to the full sun. It can reach enormous proportions and flower spikes with a length of 4 - 5 meters have been reported. The species is found in the Lake Kutubu region and has been reported from other parts of Papua New Guinea. A second variety, formerly called A. imthurmii ( = variety imthurmii) occurs in the Bismarck Archipelago and the Solomon Islands; some still regard this as a separate species.