Berosus Leach, 1817

Minoshima, Yûsuke N. & Hayashi, Masakazu, 2015, Description of the larval stages of the berosine genera Berosus and Regimbartia based on the Japanese species B. japonicus and R. attenuata (Coleoptera: Hydrophilidae), Acta Entomologica Musei Nationalis Pragae 55 (1), pp. 47-83 : 52

Genus Berosus Leach, 1817

(Figs 1–7, 17A–B, 18A)

Diagnosis. Larvae of the genus Berosus are easily distinguishable from almost all other

Hydrophilidae by the presence of tracheal gills on the abdominal segments (Fig. 1) and the reduction of spiracular atrium ( Fig. 5D );

Berosus larvae often resemble Laccobius

Erichson, 1837 in head morphology (e.g.,

ARCHANGELSKY 1997), however Berosus is distinguishable by the morphology of the clypeolabrum: right epistomal lobe absent in

Berosus ( Figs 3A , 5B ) but present in Laccobius , and left epistomal lobe bears only stout setae in Berosus ( Figs 3A , 5B ), but bears stout setae and seta-like cuticular projections in Laccobius (Y. Minoshima, personal observation).

Within Japanese genera, the genus Hydrochara Berthold, 1827 superficially resembles

Berosus by the presence of lateral projections on the abdomen (but the projections are not tracheal gills) ( MINOSHIMA & HAYASHI 2011a,

MINOSHIMA et al. 2012), the genus Laccobius in the head morphology (see above). Larvae of Berosus are distinguishable from those by the above mentioned characters, presence of tracheal gills and absence of spiracular atrium. Additional characters also separate

Berosus from Hydrochara : (1) mandibles Fig. 1. Habitus of the third instar larva of Berosus strongly asymmetrical; (2) labium more (Berosus) japonicus Sharp, 1873 .

or less reduced; (3) clypeolabrum strongly asymmetrical, left lobe strongly projecting anteriorly, right lobe absent; (4) legs without swimming hairs; (5) prostyli absent. See also a key to the genera of Japanese aquatic Hydrophilidae in MINOSHIMA & HAYASHI (2011a).

Figures

Fig. 5. Third instar larva of Berosus (Berosus) japonicus Sharp, 1873, dorsal; A – head capsule; B – anterior margin of head capsule; C – detail of setae of gFR2; D – spiracular atrium; E – spiracle in spiracular atrium.

Fig. 3. First instar larva of Berosus (Berosus) japonicus Sharp, 1873, anterior margin of head capsule, dorsal (A) and ventral (B) (both drawn from dorsal).