In the described specimens, the male has a yellow carapace and the female a yellow-orange carapace.
The described female has a cream-coloured abdomen with three dark spots at the front, a dark central stripe and two dark patches near the rear.
Selenops willinki has patches of dense hairs at the ends of its legs. Both described sexes have strong tufts around the claws of all eight feet. Even these small structures have a distinctive arrangement of hairs.
The female had been confused with a different species. A female assigned to S. willinki in a 1998 account was subsequently identified as Selenops geraldinae. The 2011 revision used additional collecting and molecular genetic evidence to confirm the association of the male and female, describing the correct female for the first time.
Among the evidence were specimens collected on Little Tobago, Trinidad and Tobago, on 16 July 2005. The molecular study lists the specimen numbers later used for the detailed male and female descriptions. Comparing their morphology with genetic evidence helped establish which sexes belonged together when appearance alone had led to an incorrect association.
An extinction-risk assessment has not been added yet.
The 2011 revision reported this spider as quite common beneath bark in dry forest on Little Tobago. The regional conservation organisation describes the island as a core area of the North-East Tobago Biosphere Reserve, where human activity is strictly limited and monitoring and conservation are priorities. Revisiting historical collection areas to examine trees, bark condition and present occurrence could help inform conservation of the spider.