Plexippus fuscus

Plexippus fuscus is a medium-sized spider, with a carapace that measures typically 3.4 mm (0.13 in) in length and 2.3 mm (0.091 in) in width, while the abdomen is typically 4 mm (0.16 in) long and 2.4 mm (0.094 in) wide. The carapace is dark brown with a black area near the eyes and a lighter area, tending towards more of an orange colour, in the middle of the thorax. It is relatively flat in shape and has a covering of dense brown hairs. The clypeus is brown and low, while the chelicerae are darker brown, with two teeth visible on the front and a single tooth to the back. The labium is also brown. The elongated abdomen is a more red-brown, also with dense brown hairs, but has a yellow belt-like marking. The underside is greyish-yellow. The spinnerets are yellow. The spider has hairy legs, the front ones being brown but the rest predominantly orange. The spider has a large and elongated epigyne with a central pocket and two very narrow gonopores. The is highly sclerotised, as are the wide entrances to the seminal ducts. This particularly long and thin pocket, its location in the middle of the epigyne, and the wide sclerotised edges of copulatory openings help the distinguish the species from others in the genus, like Plexippus paykulli, as superficially it is very similar. Only the female has been described.

The female holotype was collected in Mount LeClerc in the Guinea Highlands in 1991, at an altitude of 1,250 m (4,100 ft) above sea level. The species is ground-dwelling and has been found living in low vegetation.