Atheta (Hydrosmectomorpha) meduxnekeagensis Klimaszewski, Webster, Davies & Bourdon, 2018, new species

Atheta (Hydrosmectomorpha) meduxnekeagensis Webster and Klimaszewski, new species

(Fig. 16–23)

Holotype (male). Canada, New Brunswick, Carleton Co., Belleville “Meduxnekeag Valley Nature Preserve”, 46.1942°N, 67.6832°W, 9. VI.2008 R.P. Webster // River margin, among small cobblestones set in sand and fine gravel near water’s edge (CNC). Paratypes. New Brunswick, Queens Co., Waterborough, Grand Lake at Youngs Cove, 45.96358°N, 65.99793°W, 4.VIII.2005, R.P. Webster // Lake margin, cobblestone beach, under cobblestones (RWC) 1 female; New Brunswick, Queens Co., Cambridge, Grand Lake at Whites Cove, 45.86795°N, 66.06415°W, 4.VIII.2005, R.P. Webster // Lake margin, cobblestone beach, under cobblestones (LFC) 2 males, 2 females, (RWC) 3 males, 4 females; New Brunswick, Queens Co., Grand Lake at Goat Island, 46.0110°N, 66.0133°W, 24.VII.2007, R.P. Webster // Lake margin, on cobblestone beach under cobblestones, (RWC) 1 male, 1 female; New Brunswick, Carleton Co., Belleville “Meduxnekeag Valley Nature Preserve”, 46.1942°N, 67.6832°W, 9. VI.2008 R.P. Webster // River margin, among small cobblestones set in sand and fine gravel near water’s edge (LFC) 2 males, 3 females, (RWC) 5 males, 5 females; New Brunswick, Restigouche Co., Jacquet River Gorge PNA, 47.8257°N, 66.0768°W, 16. VI.2009 R.P. Webster // Balsam poplar forest, medium sized stream near outflow into Jacquet River on partially shaded cobblestone island among cobblestones (LFC) 1 female, (RWC) 2 males, 1 female; New Brunswick, Restigouche Co., Kedgwick Forks, 47.9085°N, 67.9057°W, 22. VI.2010, R.P. Webster // River margin, gravel bar, among gravel and cobblestones (RWC) 1 female; New Brunswick, Northumberland Co. Amostown, 46.5339°N, 66.2094°W, 11.VIII.2006, R.P. Webster, coll. // Margin of Miramichi River, among cobbles near water (RWC) 1 female.

Non-paratypes. Canada, British Columbia, N’Kwata Recreation Area at Nicola River, 511 m, elev., 50.1596°N, 121.0502°W, 2.VII.2015, R. Webster & M.A. Giguère // river margin, among cobblestones and gravel (LFC) 1 female, (RWC) 5 males, 6 females

Etymology. The species name refers to the Meduxnekeag River where the holotype and many paratypes were collected. Meduxnekeag is a Maliseet word meaning “rough or rocky at its mouth”, presumably applied to the mouth of the river itself. The entire length of this river in NB has a rocky margin including its mouth.

Diagnosis. Body subparallel, flattened (Fig. 16), length 2.6–3.0 mm (mean = 2.8 mm (N = 10), NB specimens); colour dark brown to almost black, with legs and elytra except for scutellar region paler, reddish- or yellowish-brown (Fig. 16); integument slightly glossy, forebody with fine, moderately dense punctation and faint meshed microsculpture; head slightly narrower than pronotum, eyes large and slightly protruding (Fig. 16); antennae moderately robust, antennomeres I–VII highly elongate, VIII–X slightly to distinctly elongate (Fig. 16); pronotum widest at apical third (0.51 mm) (Fig. 16); elytra distinctly elongate and broader than pronotum (0.61 mm, at shoulders), flattened, at suture about as long as pronotum (Fig. 16); abdomen subparallel, broadest before middle, gradually tapering apicad. Male. Apical margin of tergite VIII slightly (NB specimens) to distinctly (BC specimens) sinuate, with only one small lateral denticle on each side (Fig. 19a, b); apical margin of sternite VIII moderately produced, rounded (Fig. 20); tubus of median lobe of aedeagus in lateral view moderately wide, ventral margin arcuate in basal half, narrow and slightly curved ventrad apically (Fig. 17 BC, 18NB). Female. Apical margin of tergite VIII in NB specimens shallowly, broadly emarginate, angular near lateral margin (Fig. 21a), more produced, lobe-like laterally in BC specimens (Fig. 21b); sternite VIII broadly arcuate apically (Fig. 22); spermatheca short, capsule narrowly tubular and club-shaped, apical invagination small and shallow, stem straight to base with small globular swelling (Fig. 23).

Distribution. Origin: Nearctic. CANADA: BC, NB.

Habitat and collection data. Habitat. In NB, this species occurs in various cobblestone habitats along river and lake margins. Adults usually occurred among cobblestones and gravel near water’s edge, often in areas with slowed current along fast flowing rivers where there was a build-up of fine debris and growth of algae on cobblestones. This species was also found along lake margins where wave action has created conditions similar to the flowing water of rivers. BC specimens were collected from a river margin among cobblestones and gravel. Collecting period. VI–VIII. Collecting method. Hand collecting from among cobblestones near river and lake margins.

Comments. Atheta (H.) meduxnekeagensis is most likely transcontinental in Canada, but cobblestone habitats are not sufficiently sampled for aleocharines across Canada, and at present there is a substantial gap in the known distribution of this species. The specimens from BC differ somewhat from those from NB and are tentatively associated with this species and therefore excluded from the paratype series. The specimens from BC have darker elytra, are on average larger (2.9–3.1 mm (mean = 3.06 mm (N = 8) vs 2.6–3.0 mm (mean = 2.8 mm (N = 10) for NB specimens, BC specimens have a larger aedeagus (0.48 mm in length vs 0.43 mm in NB specimens) and more curved apical part of median lobe of aedeagus in lateral view with somewhat differently shaped internal structures, apical margin of male tergite VIII is slightly (NB) and distinctly sinuate (BC), and female sternite is more deeply emarginate in BC specimens than those from NB. We therefore only tentatively associate the BC population with this species. Material from intervening areas of Canada should help resolve the taxonomic status of these, at present, disjunct populations.