Atheta (Hydrosmectomorpha), Klimaszewski

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), Insecta Mundi 648, pp. 1-12: 2-3

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Atheta (Hydrosmectomorpha)

new subgenus

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 View Figures 8–15 , 16 View Figures 16–23 , 24 View Figures 24–31 , 32 View Figures 32–38 ); 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 View Figures 1–7 ); antennomeres VIII-X clearly elongate ( Fig. 8 View Figures 8–15 , 24 View Figures 24–31 , 32 View Figures 32–38 ), or subquadrate to slightly elongate ( Fig. 16 View Figures 16–23 ); last maxillary palpomere short and needle-shaped ( Fig. 7 View Figures 1–7 ); ligula elongate, partially subdivided medially ( Fig. 6 View Figures 1–7 ); mandibles long and slender, internal edge of right mandible with a small or large tooth ( Fig. 3, 5 View Figures 1–7 ), and left one with or without median tooth ( Fig. 2, 4 View Figures 1–7 ); 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 View Figures 32–38 ), or sinuate and denticulate laterally and minutely denticulate at middle ( Fig. 11 View Figures 8–15 ), or obtusely produced laterally, without teeth and deeply emarginate medially ( Fig. 26 View Figures 24–31 ); 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 View Figures 8–15 , 17, 18 View Figures 16–23 , 25 View Figures 24–31 , 33 View Figures 32–38 ). Female. Tergite VIII with apical margin truncate, sinuate or broadly emarginate ( Fig. 13 View Figures 8–15 , 21 View Figures 16–23 , 28 View Figures 24–31 , 36 View Figures 32–38 ); spermatheca small, capsule club-shaped, narrow or broad, stem moderately long, narrow, sinuate or straight and more or less swollen posteriorly ( Fig. 15 View Figures 8–15 , 23 View Figures 16–23 , 30, 31 View Figures 24–31 , 38 View Figures 32–38 ).

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.