The new species belongs to the Hydroporus puberulus -group. According to Nilsson & Holmen (1995: 40 ff, 61) this "poorly delimited" group contains both Nearctic and Palaearctic species and is characterised by the following features: (1) elytra on disc with impressed reticulation; (2) pronotum with lateral beading more or less reduced; (3) lateral margin of elytra distinctly ascending to humeral angle; (4) lateral outline of body with a slight discontinuity at level of pronotal base; (5) metacoxal processes with posterior margin conjointly truncate; (6) base of prosternal process not prolonged anteriorly as a distinct convexity; (7) third protarsomere not unusually prolonged.
Including the new species, the members of the puberulus -group are (cf. Nilsson 2001):
- Hydroporus esseri sp. n. (Palearctic)
- Hydroporus glabriusculus Aubé, 1838 (Palearctic)
- Hydroporus morio Aubé, 1838 (Holarctic) (given as member of the Hydroporus nigellus -group in Nilsson & Holmen 1995)
- Hydroporus puberulus LeConte, 1850 (Holarctic)
- Hydroporus rufinasus Mannerheim, 1852 (Nearctic)
- Hydroporus umbrosus (Gyllenhal, 1808) (Palearctic)