Berosus, Leach, 1817

Seidel, Matthias, Sýkora, Vít, Leschen, Richard A. B. & Fikáček, Martin, 2021, A review of the New Zealand Berosus (Coleoptera: Hydrophilidae) with descriptions of three new species, Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) 61 (1), pp. 243-252 : 251

Key to adults of the New Zealand species of Berosus

See also Table 1 for the summary of diagnostic characters and their comparison among species.

1 Pronotum with large rectangular dark spot covering nearly whole surface, basal half of femora black, elytral apices simple and closing tightly, small species (3.5–4.8 mm). ................................................................ 2

– Pronotum with large rectangular dark spot narrowing anteriorly, basal half of femora yellow, elytral apices expanded and leaving a gap, large species (4.4–6.0 mm). ................................................................................ 3

2 Aedeagus small, with straight parameres in lateral view, median lobe wide and nearly reaching parameral apices. Female with apical abdominal emargination rectangular. ............ B. pallidipennis ( Sharp, 1884)

– Aedeagus medium-sized, with slightly bent parameres in lateral view, median lobe narrow and much shorter than parameres. Female with apical abdominal emargination semicircular. ....................... B. maru sp. nov.

3 Aedeagus medium-sized, with strongly bent parameres in lateral view, median lobe narrow and much shorter than parameres. Female with apical abdominal emargination semicircular. ....... B. halasi sp. nov.

– Aedeagus large, with straight parameres in lateral view, median lobe narrow and much shorter than parameres. Female with apical abdominal emargination rectangular. ............................ B. muellerorum sp. nov.