Longacerus, Hlaváč, Peter, 2011

Hlaváč, Peter, 2011, Contribution to the knowledge of the tribe Mastigerina (Coleoptera: Staphylinidae: Pselaphinae, Clavigeritae), with a description of a new genus from Borneo, Zootaxa 3070, pp. 51-59 : 54-55

Longacerus gen. nov.

Type species. Longacerus giraffa sp. n. Gender masculine.

Description. Head octagonal, shiny, with strongly prolonged temples, rostrum wide, slightly convex at middle; head with very large lateral antennal cavity able to fully accomodate antennae that are then no longer visible dorsally, with well-defined constriction behind eyes that divides head in two parts: large, hexagonal anterior part that is shiny and evenly punctate on its whole surface, and long posterior part, that is matt, and with irregular microstructure; eyes very large, composed from ventral and dorsal parts; antennae three-segmented, antennomeres I and II minuscule, not visible dorsally, terminal antennomere large, somewhat triangular, with dense and long setae mainly on apical two-thirds and apex; venter of anterior part of head densely punctate similar to dorsal anterior part; venter of prolonged, posterior part with rough microstructure similar to dorsal posterior part.

Pronotum shiny, with punctation similar to that of anterior part of head, slightly wider than head, heptagonal, longest at middle, its base triangular, deeply recessed into elytra, widest at posterior angles, all angles well-defined, sharp, pronotum lacking foveae or sulci; scutellum not visible.

Venter with prosternum shiny and densely punctate; procoxae confluent; mesoventrite shiny, short, about three times shorter than metaventrite, its median part with rough irregularly punctation, lateral parts with deep, smooth impressions able to fully accommodate profemora; basal mesoventral process short and truncate; metaventral process longer, rhombic, with well-defined carina at level of posterior border of mesocoxae; mesocoxae separated; whole metaventrite densely punctate; metacoxae separated by large, truncate, basal metaventral process; metaventrite as well as first visible sternite (III) with large impressions to accommodate meso and metafemora, first visible sternite more than five times shorter than second (IV), sternites V–VII clearly visible but together shorter than sternite III.

Elytra shiny and with regular punctation similar to that of pronotum, almost twice as long as pronotum and longer than abdomen, lacking setae; humeri and basal angles very prominent.

Abdomen shiny, composite tergite (IV–VI) with large, transverse basal basin at about half of its length bordered by well-developed, sharp U-shaped carina bearing two fine triangular trichomes on each side. Paratergites of composite tergite elongate and bearing dense, golden trichome, tergites VII and VIII also visible dorsally but very short, especially VII visible only as line.

Legs short, tibiae flat.

Sexual dimorphism. Male unknown, but likely to have modified mesofemora and possibly mesotibiae, bearing spines and spurs.

Remarks. Longacerus is most closely related to Pseudacerus , sharing with this genus the distinct shape of the 3-segmented antennae, very large lateral antennal cavity able to fully accomodate the antennae that are then no longer visible dorsally, and similar, heptagonal shape of the pronotum. Both genera have the antennae with the terminal antennomere elliptically prolonged and bearing dense setae mainly in the apical half. This is a unique feature in the supertribe Clavigeritae readily separating both genera from any other members of the supertribe.

Host ant. Unknown. The holotype was collected by a flight interception trap in a lowland dipterocarp primary forest.

Distribution. Borneo (Sabah).

Etymology. The name is a combination of the Latin adjective ‘ longus ’, referring to the long, posteriorly prolonged head, and ‘- cerus ’ the second part of the name Pseudacerus , reflecting the close relationships between the two genera.