Epactophanes muscicolus is morphologically a variable species, having a small, slender and vermiform body.
The exopod in the first four legs has three segments, while the endopod is 2-segmented. The legs 2–4 has small endopods. The operculum has 4–8 spines, which is smaller than in E. richardi. The caudal ramus is about 1.5 times as long as wide and the inner margin is armored with 2–3 small spines. The antennule consists of seven segments.
Female: Length 0.35–0.49 mm
Male: Length 0.27–0.40 mm
Ecology and distribution
Epactophanes muscicolus is recently found in Norway. It has a scattered distribution and is found in streams, moss (ditch in coniferous forest) and in the littoral zone of lakes. It is distributed in Northern, Middle, Eastern and Western Norway from 14 to 420 m a.s.l. Many authors consider this taxon to consist of many local forms or varieties, all belonging to the cosmopolitan species E. richardi.