Stenaelurillus fuscatus

Stenaelurillus fuscatus is a species of jumping spider in the genus Stenaelurillus that lives in Kenya and Tanzania. The species was first identified in 2000 by Wanda Wesołowska & Anthony Russell-Smith, and named for the Latin word for darkish. The spider is medium-sized with a carapace between 2.5 and 3.2 mm long and an abdomen that is between 2.8 and 3.6 in in length. The female carapace is dark brown and has two white stripes and a pattern of a triangle and spots on the abdomen. The colouration is similarly dark but the patterns are less clear. The male abdomen is dominated by a dark scutum. The female is also darker overall, with brown rather than the yellow spinnerets and light brown chelicerae of the male. The male has a hook near the base of the embolus that differentiates it from other species in the genus, while the female's wide insemination ducts sets it apart from the similar Stenaelurillus darwini.

Taxonomy
Stenaelurillus fuscatus was first described by Wanda Wesołowska & Anthony Russell-Smith in 2000. The species name is the Latin word that means darkish. It was placed in the genus Stenaelurillus, first raised by Eugène Simon in 1886. The genus name relates to the genus name Aelurillus, which itself derives from the Greek word for cat, with the addition of a Greek stem meaning narrow. It was placed in the subtribe Aelurillina in the tribe Aelurillini by Wayne Maddison in 2015, who listed the tribe in the clade Saltafresia. Two years later, in 2017, it was grouped with nine other genera of jumping spiders under the name Aelurillines.

Description
The spider is medium-sized. The male has a carapace that is 2.6 mm long and 2 mm wide and abdomen that is 2.8 mm long and 2.0 mm wide. The carapace is dark brown and has two faded white stripes on the thorax. The abdomen is very hairy, with dense long black hairs dominating, although there is a small corridor of white hairs on the dark brown scutum that covers the majority of the surface. Underneath, the abdomen is yellowish, but this is hard to see. The eye field is small, black and bristly. The chelicerae and clypeus are light brown, and there three small teeth visible. The spider has long hairy yellow spinnerets. The legs and pedipalps are brownish, the pedipalps also having long black hairs. The palpal bulb has a very large bulb at the rear while the embolus has a distinctive hook near the base. Other than the sexual organs, the male is similar to Stenaelurillus darwini and Stenaelurillus uniguttatus.

The female is similar to the male in shape but slightly larger. The carapace is between 2.5 and 3.2 mm long and between 1.95 and 2.35 mm wide while the abdomen has a length between 3 and 3.6 in and width of 2.6 and 2.95 mm. The carapace is similar in colour to the male but the white stripes are more pronounced and extend onto the abdomen. The abdomen also has a more prominent pattern with a white triangular marking and oval spot formed of white scales. There are also numerous speckles visible underneath. The clypeus is yellow-brown but the chelicerae and legs are brown. The spinnerets also have a browner tint. The epigyne is flat with visible structures and a barely visible pocket. The copulatory openings are widely spaced and ovoid.. It has very short and wide insemination ducts and ovoid spermathecae. The female can be distinguished from Stenaelurillus darwini by the wider insemination ducts. Compared to Stenaelurillus latibulbis, the copulatory organs lack sclerotization.

Distribution and habitat
The species is endemic to Tanzania. The holotype was found near the Umba River in the Mkomazi National Park in 1995. It was also subsequently found in the forests of Matthews Range and the coastal regions of Kenya. It thrives in exposed environments, like rocks.