Eusclerus SHARP 1886

Assing, V., 2011, A revision of Eusclerus SHARP, with a redescription of Sciocharis buphthalma SCHEERPELTZ (Coleoptera: Staphylinidae: Paederinae: Medonina), Linzer biologische Beiträge 43 (2), pp. 1169-1177 : 1170-1171

Eusclerus SHARP 1886

Eusclerus SHARP 1886: 375 f.

T y p e s p e c i e s Eusclerus rugifrons SHARP 1886 ; designation by LUCAS (1920).

R e d e s c r i p t i o n: Body of small size, body length 2.8-3.5 mm. Habitus similar to that of Sunius STEPHENS 1829 and Neosclerus.

Head with coarse and dense punctation ( Figs 3 , 8 ). Eyes conspicuously large ( Figs 2 , 6 ). Neck broad, slightly less than half as broad as maximal head width (including eyes). Gular sutures narrowly separated, distance between sutures in the middle subequal to width of antennomere III. Antenna of similar morphology as that of Sunius and Neosclerus. Mandibles moderately slender and with three distinct molar teeth ( Fig. 25 ). Labrum distinctly transverse; anterior margin notched in the middle, without distinct teeth on either side of this notch ( Fig. 26 ). Maxillary palpus four-jointed; palpomere III 2-2.5 times as long as broad, much larger than palpomeres I-II; palpomere IV fine, short, and needle-shaped. Labial palpus three-jointed ( Fig. 27 ); ligula with 12 stout setae ( Fig. 28 ).

Pronotum approximately as wide as long and somewhat narrower than head ( Figs 2 , 6 ); punctation dense and granulose; midline posteriorly with narrow impunctate band ( Figs 4 , 8 ). Elytra of variable length. Protarsi apparently without sexual dimorphism, weakly dilated. Metatarsus of variable length; metatarsomeres I-IV of gradually decreasing length; I somewhat longer than II.

Abdomen narrower than elytra; punctation fine, dense on tergites III-VI, somewhat sparser on posterior tergites.

: sternite VII with weakly concave posterior margin, otherwise unmodified; sternite

VIII with relatively small posterior excision.

C o m m e n t: In the original description of the genus, SHARP (1886) erroneously states that the labrum is "rounded in front, but divided by a deep angular incision almost to the base" and that the mandibles have "feeble teeth". The shape of the labrum is the only character indicated by CAMERON (1924) to distinguish Neosclerus from Eusclerus . The erroneous description of the mandibles is evidently based on the condition of the holotype of E. rugifrons , in which the teeth are somewhat reduced as a result of either damage or wear.

D i a g n o s i s: The genus is characterised and distinguished from other genera of Medonina resembling Sunius particularly by the combination of conspicuously large eyes and a granulosely punctate pronotum. Species of Sciocharis with similarly large eyes have a bidentate anterior margin of the labrum, bidentate mandibles, and an antenna of different morphology (antennomeres I-II enlarged and III-XI thin). In Neosclerus, the punctation of the pronotum is not granulose and the ligula is of different shape and chaetotaxy.

D i v e r s i t y: The genus currently includes two species from Guatemala.

Figures

Figs 1-4: Eusclerus rugifrons SHARP, holotype: (1) habitus; (2) forebody; (3) median dorsal portion of head; (4) median dorsal portion of pronotum. Scale bars: 1: 1.0 mm; 2: 0.5 mm; 3-4: 0.2 mm.

Figs 5-11: Eusclerus sordidus SHARP, holotype: (5) habitus; (6) forebody; (7) median dorsal portion of head; (8) median dorsal portion of pronotum; (9) male sternite VIII; (10-11) aedeagus in lateral and in ventral view. Scale bars: 5: 1.0 mm; 6: 0.5 mm; 7-9: 0.2 mm; 10-11: 0.1 mm.

Figs 21-28: Sciocharis buphthalma SCHEERPELTZ (21-24) and Eusclerus sordidus SHARP (25-28): (21, 27) labium; (22, 28) ligula; (23) male sternite VII; (24) male sternite VIII; (25) mandibles; (26) labrum. Scale bars: 23-25: 0.2 mm; 21, 26-27: 0.1 mm; 22, 28: 0.05 mm.