Atheta (Hydrosmectomorpha) Klimaszewski, new subgenus
Creators: name: Klimaszewski, Jan
name: Webster, Reginald P.
name: Davies, Anthony
name: Bourdon, Caroline
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Staphylinidae
Atheta

description: Subgenus Hydrosmectomorpha Klimaszewski and Webster, new subgenus
Type species of subgenus. Atheta (Hydrosmectomorpha) meduxnekeagensis Webster and Klimaszewski, new species.
Etymology. Hydrosmectomorpha, meaning body like Hydrosmecta, an adjective derived from the generic name Hydrosmecta to which species of this subgenus are externally superficially similar. The gender is feminine.
Description. Body narrowly elongate, subparallel, slightly flattened (Fig. 8, 16, 24, 32); head rounded, pubescence on disc directed obliquely towards midline, postocular carina strong and complete, eyes large, each longer than postocular area of head in dorsal view; labrum shallowly emarginate apically (Fig. 1); antennomeres VIII-X clearly elongate (Fig. 8, 24, 32), or subquadrate to slightly elongate (Fig. 16); last maxillary palpomere short and needle-shaped (Fig. 7); ligula elongate, partially subdivided medially (Fig. 6); mandibles long and slender, internal edge of right mandible with a small or large tooth (Fig. 3, 5), and left one with or without median tooth (Fig. 2, 4); pronotum slightly transverse, about one fifth (0.2) wider than long, broadest at apical third, pubescence on disc directed anteriad along midline, antero-laterad on each side forming arcuate lines, hind angles of disc evident to distinct, obtusely rounded, hypomera entirely visible in lateral view; elytra transverse, at suture 2/3 to 4/5 as long as wide, distinctly broader than pronotum, flat, shoulders rounded, subrectangular, posterior margin of each elytron broadly arcu- ate, latero-apical emarginations weakly defined, pubescence on disc directed obliquely posteriad from suture; abdomen subparallel; legs long. Male. Tergite VIII with apical margin truncate and slightly sinuate medially (Fig. 34), or sinuate and denticulate laterally and minutely denticulate at middle (Fig. 11), or obtusely produced laterally, without teeth and deeply emarginate medially (Fig. 26); tubus of median lobe of aedeagus moderately long, in lateral view with ventral margin straight to arcuate, apex moderately curved ventrad, internal sac structures small and inconspicuous, ventral margin of crista apicalis moderate to long, projecting at an angle to bulbus, rectangular basally in some specimens also at base of median lobe (Fig. 9, 17, 18, 25, 33). Female. Tergite VIII with apical margin truncate, sinuate or broadly emarginate (Fig. 13, 21, 28, 36); spermatheca small, capsule club-shaped, narrow or broad, stem moderately long, narrow, sinuate or straight and more or less swollen posteriorly (Fig. 15, 23, 30, 31, 38).
Discussion. Hydrosmectomorpha, is distinguishable from other subgenera of Atheta by the following combination of characters: body narrow, subparallel and flattened; elytra markedly broader than remain- der of body; distinctive pattern of pubescence on pronotum and elytra (described above); antennomeres VIII–X distinctly to slightly elongate; ligula weakly subdivided apically; legs long; apical margin of male tergite VIII lacking prominent teeth; spermatheca small, with stem short and simple, straight or sinuate; all known species occur among cobblestones and gravel along margins of clear, fast flowing rivers, near the outflow of brooks into rivers, and along lake margins with wave action.
The median lobe of the aedeagus in Hydrosmecta has a blade-like, triangular projection at the base of the tubus in lateral view to which parameres are attached, this structure is narrowly elongate along ventrally flat part of bulbus, in Hydrosmectomorpha. Male tergite VIII in Hydrosmecta is truncate apically and not modified, while in Hydrosmectomorpha it is truncate and slightly emarginate, deeply notched, or with minute teeth. The stem of spermatheca in Hydrosmecta, is coiled posteriorly, broadly looped, or irregularly twisted, while in Hydrosmectomorpha it is straight or slightly sinuate with small apical swelling. The external similarity of Hydrosmectomorpha species (e.g., flattened body, similar pronotal pubescence pattern), to those of Hydrosmecta represent convergent evolution and adaptation to live among cobblestones, gravel and sand along margins of clear, fast-flowing water.
description: Published as part of Klimaszewski, Jan, Webster, Reginald P., Davies, Anthony & Bourdon, Caroline, 2018, Description of Hydrosmectomorpha Klimaszewski and Webster, a new subgenus of Atheta C. G. Thomson, with three new Canadian species (Coleoptera: Staphylinidae: Aleocharinae), pp. 1-12 in Insecta Mundi 648 on pages 2-3, DOI: 10.5281/zenodo.3708236