Greek arachnion, spider's web, + -odes, having the form or nature of; a puzzling name for this genus. Plants medium-sized to large, terrestrial. Rhizomes short-creeping to decumbent, scaly. Fronds to 1.5 m long. Stipes grooved, clothed with tan, linear-triangular scales, scales not peltate or clathrate, cross section at base revealing several small, round vascular bundles forming a semicircle or ring. Blades 2-pinnate to 5-pinnate, becoming pinnatifid distally and tapering to pointed tips; rachises grooved, ridges on adaxial surfaces continuous with those of pinna costae. Pinnae triangular-lanceolate, tips acute, upturned, basiscopic basal pinnules of basal pinnae much larger than acroscopic basal pinnules. Ultimate segments sharply toothed at tips. Veins free. Indusia kidney-shaped or rounded. A widely distributed but poorly known genus of 40-50 species found in moist mountain forests from northeastern India to southern Japan to New Zealand, in the American Tropics, and in Polynesia. Represented in Hawai 'i by a single endemic species.