More information on Arachnis 'spider' orchids can be found here.

There are about twenty large, often climbing monopodial epiphytic species in this genus distributed throughout Southeast Asia, New Guinea, and the Solomon Islands.
Species produce a highly variable inflorescence; short or long, erect or pendent, simple or branched, bearing few to many flowers. The long-lasting flowers
typically have large sepals and petals, a small hinged lip, and are often barred in brown color. Species are closely allied to genus Vanda and Renanthera.