Georissus Latreille, 1809

Yasuda, Kohei & Yoshitomi, Hiroyuki, 2022, Revision of the genus Georissus (Coleoptera, Hydrophiloidea, Georissidae) of Japan, European Journal of Taxonomy 817 (1), pp. 111-142 : 115-116

Subgenus Georissus Latreille, 1809

Georissus Latreille, 1809: 377 . Type species: Pimelia pygmaea Fabricius, 1798 (= Byrrhus crenulatus Rossi, 1794 ) [by monotypy].

Georyssus [unjustified emendation] – Stephens 1828: 105.

Redescription

HEAD. Clypeus uneven, with groove along the anterior margin. Surface of clypeus provided with large granules densely; slr reaching to anterior margin of frons. Frons bearing median longitudinal groove to vertex; lsa narrow, not connecting each other. Granulation of frons sparse, indistinct. Mandibles ( Fig. 4J ) relatively small; median lateral margin curving strongly, apex bidentate, mola well developed. Antennae ( Fig. 4M ) relatively long; antennomere 4 as wide as antennomere 3, about twice as long as antennomere 3; pubescence of club short. Labrum ( Fig. 4D ) not protruding anteriorly; spines on anterior margin indistinct. Apical labial palpomere ( Fig. 4G ) oblong oval, with long spines densely. Galea ( Fig. 4A ) bearing long dense setae.

PRONOTUM. Half oval, slightly projecting laterally in lateral portion, without sdn. Lateral margin except anterior portion regularly provided with granules. First half of pronotal disc irregularly bearing foveae and grooves, the second half of disc smooth, but with median longitudinal groove reaching near posterior margin.

E LYTRA. Bearing seriate large punctures. Elytral interstices smooth, not highly raised. Humeral bulges distinct, smooth. Lateral ridges on each elytron indistinct.

ABDOMEN. Ventrites sparsely bearing granules. Ventrites 1–2 provided with a pair of ventral teeth.

MALE GENITALIA. Aedeagus wide, subparallel-sided. Parameres densely provided with small spines on antero-internal portion, as long as phallobase. Median lobe little shorter than parameres. Basal struts short. Phallobase wide; basal foramen large, but indistinct.

FEMALE GENITALIA. Ovipositor relatively elongate to longitudinal portion. Two long setae of gonostylus long.

Remarks

This subgenus is distinguished by the following characteristics: lacking sdn (present in Neogeorissus ); posterior portion of pronotal disc smooth, with median longitudinal groove (uneven, with granules or depression in other subgenera); elytral interstices smooth, not highly elevated (in contrast to uneven, granulated in other subgenera); parameres provided with small dense spines on the anterior portion (even in other subgenera).

The members of this subgenus are often covered with sand or mud when they are alive ( Bameul 1989; Shepard 2003; Litovkin 2018; Fikáček 2019). Bameul (1989) reported that adults of G. crenulatus attach sand grains to their body surface using oral secretions and their legs.

Figures

Fig. 4. Mouth parts and antennae of Georissus spp. A–C. Left maxillae. D–F. Labrum. G–I. Labial palpi. J–L. Left mandibles. M–O. Left antennae. A, D, G, J, M. G. (G.) canalifer Sharp, 1888. B, E, H, K, N. G. (Ni.) granulosus Satô, 1972. C, F, I, L, O. G. (Ne.) japonicus Satô, 1972. Scale bars = 0.1 mm.