Berosus halasi sp. nov. (Figs 1D, H, K; 2D, H) Type material. Hඈඅඈඍඒඉൾ: J (NZAC), “NEW ZEALAND: MC, Mid / Canterbury, 6km W of / Hakatere, Lake Roundabout, / S43°37.3′, E171°05.9′, 660m, / 8.ii.2018, J. Hájek & P. Hlaváč / lgt. // DNA isolate: / NZ355.1 / extracted by M. Seidel 2017 / DNA extract deposited in / Natural Museum, Prague // HOLOTYPE / Berosus halasi n. sp. / Seidel et al. 2019”. Pൺඋൺඍඒඉൾඌ: NEW ZEALAND: SඈඎඍΗ Iඌඅൺඇൽ: Mid Canterbury: 1 J 1 ♀ (NMPC): same data as holotype. Central Otago: 1 ♀ (NZAC): Maniololo [=Maniototo], 94, Lewis coll., No. 5523; 1 ♀ (MONZ): “Maniololo [=Maniototo], 94, Lewis Coll., No 5524; 1 ♀ (MONZ): “.Maniololo [=Maniototo], 94, Lewis Coll., No 5526. Description of adults [characters identical to B. pallidipennis redescription are not repeated]. Body length 5.3–6.0 mm (holotype: body length: 5.8 mm; humeral width: 1.9 mm). Shape elongate ellipsoid (Figs 2D, H). Coloration. Pronotum with yellowish ground coloration, bearing large median dark metallic spot which is narrowly rectangular in anterior half and widely semicircular posteriorly, not reaching posterior margin. Maxillary palpi with palpomere 4 darkened in apical fourth. Legs with trochanters and basal sixth of femora black, other parts testaceous. Dorsum. Pronotal surface without apparent setae. Surface of elytra smooth in males, with mesh-like microsculpture in females. Elytral apices slightly projecting in both sexes (slightly more in females), making elytral apices slightly divergent from each other and leaving a small gap between them when elytra are closed. Ventrum. Mesoventrite without median keel, only with a low posteromedian process. Abdominal ventrite 5 with a wide, very shallow apical notch delimited laterally by small teeth in male, with a deep semicircular notch in female. Legs. Male protarsus with adhesive soles on tarsomere 1, which is ca. twice as thick as following tarsomeres; tarsomere 4 as long as tarsomeres 1–3 combined. Male genitalia. Total length 1.65 mm. Paramere long, narrow, gradually acuminate, straightly projecting towards ventral side in lateral view. Apices pointed, slightly bent mesally in dorsal view. Median lobe much shorter than parameres, its width in apical half only slightly wider than the width of paramere. Differential diagnosis. Berosus halasi sp. nov. is easy to distinguish from B. pallidipennis and B. maru sp. nov. by its large body size and anteriorly narrowing pronotal spot. In both these characters it resembles B. muellerorum sp. nov. from which it can be distinguished by the shape of the apical abdominal emargination in females, and the morphology of the aedeagus in males. Etymology. This species is dedicated to Pavel Halaš (Prague, Czech Republic) as a thank for his support of the entomology. The name is a noun in genitive singular case. Habitat. In 2016, this species was collected in the non-vegetated shallow littoral zone of Lake Roundabout where it was swimming among stones in clear water (Fig. 3E). The second attempt to collect the species at this locality in 2017 was unsuccessful, possibly because of high abundance of algae that were not present in the lake in 2016. Distribution (Fig. 3A). The species is only known from two localities in the central montane non-forested part of the South Island (Mid Canterbury and Otago) and may be endemic to this zone.

Published as part of 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, pp. 243-252 in Acta Entomologica Musei Nationalis Pragae (Acta. Ent. Mus. Natl. Pragae) (Acta. Ent. Mus. Natl. Pragae) 61 (1) on page 248, DOI: 10.37520/aemnp.2021.014, http://zenodo.org/record/5354355