However, four-eyed (Opopaea viamao), two-eyed (e.g. Coxapopha, Diblemma) and even completely eyeless species (e.g. Cousinea, the cave-dwelling Blanioonops) are also known.

Examples include heavily modified mouthparts (e.g. Coxapopha, Xyccarph), sternal pouches (sometimes alternatively called holsters; e.g. Grymeus) and extensions of the carapace (e.g. Ferchestina, Unicorn).

The genus Opopaea, for example, exhibits an expanded palpal patella while male Ischnothyreus are characterized by completely sclerotized, pitch-black pedipalps.

Members of the genus Orchestina are believed to be able to jump, as both sexes have greatly enlarged femora on the fourth leg pair.

They are generally found in the leaf litter layer and under rocks, but they also constitute a significant component of the spider fauna living in the canopy of tropical rainforest.