Trimiina Bowman, 1934

Owens, Brittany E. & Carlton, Christopher E., 2016, Collecting in the Museum: New Species, Taxonomic Changes, and Range Extensions of Euplectite Pselaphinae (Coleoptera: Staphylinidae) of the Southeastern United States, The Coleopterists Bulletin 70 (3), pp. 611-633 : 611-633

Subtribe Trimiina Bowman Actium Casey, 1886

Diagnosis. Males. Head: Rounded trapezoidal, slightly wider than long, frontal region with narrow, shallow sulcus between vertexal foveae; antennal acetabula separate, antennomeres 1– 8 unmodified, antennomeres 9–10 forming distinct club; labrum of normal form for tribe, bearing pair of sensory pegs, mandibles broadly sickle-shaped, maxillae and labium typical for subfamily, labial palpi minute, 2-segmented, maxillary palpi unmodified, palpomere 1 minute, obliquely joined to palpomere 2, palpomere 2 pedunculate, narrower in basal third, slightly expanded and rounded distally, palpomere 3 subtriangular, palpomere 4 widest, unmodified, bearing apical palpal cone; gula simple and slightly rounded anteriorly, paired gular foveae present. Thorax: Pronotum as long as wide, disc evenly convex, margin incomplete, antebasal transverse sulcus present, margin delimited by lateral antebasal foveae, longitudinal median sulcus absent, basolateral fovea present, prosternum slightly convex, lateral procoxal foveae present; mesoventrite with single median mesoventral fovea, paired lateral mesoventral and mesocoxal fovea present, single median mesoventral fovea present, mesocoxae contiguous; paired lateral and median metaventral foveae present, metacoxae conjunct; legs variously modified; elytra with sutural fovea and striae, antebasal discal foveae and subhumeral foveae present, discal striae present; lateroapical cleft present; wings present or absent. Abdomen: Visible tergite I with small basolateral foveae and basal carinae; visible tergites II and III occasionally with basal carinae; ventrite II bearing large basolateral foveae and variable lateral setose modifications; ventrites III and IV with lateral foveoid depressions and various modifications; ventrites V–VI occasionally with expanded setae medially; ventrite VII forming ovoid penial plate. Genitalia: Laterally compressed; median lobe large; right and left parameres distinct; internal spines well-developed.

Females. Externally similar to males except eyes smaller with fewer facets, secondary sexual modifications to legs and abdominal ventrites absent, and ventrite VII not modified into penial plate (revision, Grigarick and Schuster 1971).

Notes. Actium is one of the largest euplectite genera in North America, currently containing over 30 described species. The majority of species in this genus are known from the Pacific coast states of the US, mostly from California and Oregon. Specimens have been collected by sifting forest litter, litter along streams and springs, or from dead wood. Most species are represented by singletons or small series in museums. No new species have been described from this genus in eastern North America since the last revision by Grigarick and Schuster (1971) .

Previous to the current publication, Actium impunctatum ( Brendel, 1865) was the only representative of this genus known from southeastern USA, being taken from several localities in Virginia, West Virginia, and North Carolina. The new species described herein, Actium riobuffaloensis new species is known from northern Arkansas. This species is externally distinct from A. impunctatum and does not fall into the same species-group based on the morphological criteria of Grigarick and Schuster (1971). It lacks setal modifications or projections on the abdominal ventrites, excluding it from existing eastern species-groups.

Members of Actium may be easily confused with other small euplectites. Further examinations of the limited specimens available for study in museums may yield new species from similar habitats in the southeastern USA.

KEY TO MALES OF THE SOUTHEASTERN NORTH AMERICAN SPECIES OF ACTIUM CASEY (Modified from Grigarick and Schuster 1971)

1. Row of setae on ventrite III present ............... ............................. A. impunctatum (Brendel)

1.′ Row of setae on ventrite III absent................. ..................... A. riobuffaloensis Owens and Carlton , new species