Arachnis Blume,
Bijdr. (1825) 365
Monopodial epiphytic or terrestrial plants. Stem usually much elongated, sometimes climbing, with many distichous leaves. Leaves sheathing at the base, glabrous, deciduous, duplicate, leathery. Inflorescence lateral, a raceme or a panicle. Flowers medium-sized to rather large, showy. Sepals free. Petals free, fairly similar to the lateral sepals. Lip not spurred, but somewhat sac-shaped at the base, hinged to the column. Column-foot absent. Pollinia 4, about equal-sized, arranged in 2 bodies, solid, caudicles absent, stipe short and broad, viscidium present.
Distribution
Southeast Asia, Malaysia, Indonesia, the Philippines, Papua New Guinea, east to the Solomon Islands; about 13 species.
Distribution in the Philippines
Luzon (Isabela, Rizal, Quezon), Palawan, Mindanao (Lanao, Surigao), Tawi-Tawi; 2 species.
Habitat
Epiphytes in lowland and montane forest.
Notes
Certain species of Arachnis are well-known as 'scorpion orchids', these are widely cultivated and extensively used in hybridisation. Among similarly popular related genera (e.g. Vanda, Renanthera, Papilionanthe) they are distinguished by the lip being elastically hinged to the base of a footless column and by lacking a true spur. The genera Vandopsis, Armodorum and Esmeralda appear to be the nearest relatives of Arachnis.