Review of Canadian species of the genera Gnathusa Fenyes, Mniusa Mulsant & Rey and Ocyusa Kraatz (Coleoptera, Staphylinidae, Aleocharinae)

Abstract Four species of Gnathusa Fenyes (G. alfacaribou Klimaszewski & Langor, G. caribou Lohse, G. eva Fenyes, and G. tenuicornis Fenyes) occur in the Nearctic and in Canada. Three species of Ocyusa Kraatz (O. asperula Casey, O. californica Bernhauer, O. canadensis Lohse), and three species of Mniusa Mulsant and Ray (M. minutissima (Klimaszewski & Langor), M. yukonensis (Klimaszewski & Godin), and M. odelli Klimaszewski & Webster, sp. n.), are known from the Nearctic and all but O. californica occur in Canada. The recently described Gnathusa minutissima Klimaszewski and Langor and Ocyusa yukonensis Klimaszewski and Godin, are transferred here to the genus Mniusa Mulsant & Rey. New provincial and state records are reported for: G. eva (Alberta), G. tenuicornis (Alberta, Oregon, and New Brunswick), O. canadensis (New Brunswick and Newfoundland), M. minutissima (New Brunswick), and M. yukonensis (Nova Scotia, New Brunswick, Quebec, and British Columbia). The female of M. yukonensis was discovered and is illustrated for the first time. The genus Mniusa is reported for the first time from Canada and represents the first confirmed generic record for North America. Keys for identification of all Canadian species, images of body and genital structures, maps showing distribution mainly in Canada, and new bionomics data are provided.


Introduction
described the genus Gnathusa and two species from the Nearctic region, G. eva from California and G. tenuicornis from British Columbia. More recently, Lohse (Lohse et al. 1990) described a northern species, G. caribou from Canada (YT, NWT) and Alaska, and later Klimaszewski and Langor (Klimaszewski et al. 2011) described an additional species, G. alfacaribou, from Newfoundland and Labrador, a species closely related to G. caribou. Recently, more specimens of Gnathusa have become available for study, resulting in new range extensions but no additional new species. It appears that species of this genus are confined to the Rocky Mountains and northern Canada.
Gnathusa is sometimes confused in North American collections with some species of the genus Ocyusa Kraatz (1856). Ocyusa was originally described in Europe and currently includes nine species, excluding two species of Mniusa Mulsant & Rey (Smetana 2004, in Löbl andSmetana 2004). However, Palm (1972) and Ashe (2000) considered Mniusa to be a subgenus of Ocyusa. Osswald et al. (2013) proposed a molecular phylogeny of the rove beetle tribe Oxypodini where they recognised Mniusa and Ocyusa as two distinct genera. They classified Mniusa as closely related to Gnathusa, and Ocyusa as closely related to the Oxypoda, Devia, Ilyobates, Tetraleucopora and Ocalea group of genera. Assing (1998) revised species of Palaearctic Zoosetha Mulsant & Rey and provided a taxonomic history of related genera including Ocyusa. Ocyusa asperula was the first species of this genus described in the Nearctic region, from Rhode Island (Casey 1894). It was later reported by Bernhauer (1906) from Iowa and Massachusetts under the synonymic name O. brevipennis. Webster et al. (2009) reported it for the first time from Canada in New Brunswick. Bernhauer (1906) described O. californica from California, and this species is not found in Canada. Lohse (Lohse et al. 1990) described a new northern species, O. canadensis from Yukon Territory and Alaska. Brunke et al. (2012) reported this species from Ontario, and we report it here from Newfoundland and Labrador, and New Brunswick. Klimaszewski et al. (2011Klimaszewski et al. ( , 2012 described Gnathusa minutissima from the province of Newfoundland and Labrador, and Ocyusa yukonensis from Yukon Territory, but they are here transferred to the genus Mniusa on the basis of pronotal pubescence along midline directed anteriad in apical third of median line of disc, absence of fronto-clypeal suture, L-shaped spermathecal neck connected to thin stem, and apical margin of male tergite 8 sinuate laterally and produced medially. Mniusa minutissima is newly recorded from New Brunswick. Recently, M. yukonensis was described from the Yukon Territory under the genus Ocyusa , and we now provide new records of this species from British Columbia, Quebec, Nova Scotia, and New Brunswick. Here, we have discovered and described another Mniusa species, M. odelli, which has similar genitalic features to those of M. yukonensis, but has a different body form. To facilitate identification of species of Gnathusa, Mniusa, and Ocyusa in Canada, we review their diagnostic features, and provide keys to identification. We also provide extensive illustrations of diagnostic characters, including external body images and genital structures.

Materials and methods
Over 140 adults of the genus Gnathusa and 100 adults of Ocyusa and Mniusa from Canada and the United States were studied, and most specimens were dissected to examine the genital structures and in some cases, mouthpart structures. The genital structures were dehydrated in absolute alcohol, mounted in Canada balsam on celluloid microslides, and pinned with the specimens from where they originated. Images of the entire body and the genital structures were taken using an image processing system (Nikon SMZ 1500 stereoscopic microscope; Nikon Digital Camera DXM 1200F, and Adobe Photoshop software).
Morphological terminology mainly follows that used by Seevers (1978) and Klimaszewski et al. (2011). The ventral side of the median lobe of the aedeagus is considered to be the side of the bulbus containing the foramen mediale, the entrance of the ductus ejaculatorius, and the adjacent ventral side of the tubus of the median lobe with internal sac and its structures (this part is referred to as the parameral side in some recent publications); the opposite side is referred to as the dorsal part. In the species descriptions, microsculpture refers to the surface of the upper forebody (head, pronotum and elytra).
The morphology of antennae and mandibles, body proportions, density of punctures on the forebody, and the shape of the median lobe of the aedeagus and the spermatheca provide the best characteristics for species identification in Gnathusa, Mniusa and Ocyusa.

Depository/institutional abbreviations AAFC
Agriculture and Agri-Food Canada, Atlantic Cool Climate Crop Research Centre, St. John's, Newfoundland and Labrador, Canada. AMNH American Museum of Natural History, New York, New York, USA.

Key to Canadian species of Gnathusa
New provincial and territorial records are indicated in boldface font.
Bionomics. Adults were captured in clear-cut Sitka spruce forest on Vancouver Island and in moss and gravel at the edge of small pools at other localities in the interior of British Columbia (Klimaszewski and Winchester 2002). Additional specimens were found in British Columbia in a 1-year-old harvested Douglas-fir stand. In westcentral Alberta, adults were collected in pitfall traps deployed in Upper Cordilleran coniferous forests, including subxeric lodgepole pine forests, mesic white spruce and lodgepole pine stands and spruce-dominated subhygric and hygric forests, but not in deciduous-dominated forest or in grassy or shrubby meadows. In Alberta, adults also emerged from lodgepole pine trees infested by bark beetles. In the Yukon Territory, adults were found in a squirrel midden in spring, probably overwintering, and in a coniferous woodchip pile.
Distribution. This native Nearctic species was described from specimens captured in Glacier, British Columbia, later recorder from Yokon, and is herein recorded for the first time from Alberta and New Brunswick (four female specimens tentatively identified as this species) (Map 2). In the United States, this species was previously known from California (Fenyes 1921, Moore and Legner 1975, Klimaszewski and Winchester 2002, and is herein recorded for the first time from Oregon. Bionomics. Adults were captured in a clear-cut Sitka spruce forest on Vancouver Island and in moss and gravel at the edge of small pools in British Columbia (Klimaszewski and Winchester 2002). Other adults were found in a subalpine meadow at 3000 feet, in cold moss and gravel along the edges of streams. The Yukon specimens were taken from mixed aspen and spruce forest by sifting litter. In west-central Alberta, adults were collected in pitfall traps deployed in Upper Cordilleran coniferous forests, including subxeric lodgepole pine forests, mesic white spruce and lodgepole pine stands and and spruce-dominated subhygric and hygric forests, but not in deciduous-dominated forest or in grassy or shrubby meadows. The New Brunswick specimens were taken from moss and leaves under alders near a brook in an eastern white-cedar swamp and from under cobblestones and gravel in sand on a partially shaded cobblestone bar near the outflow of a brook into a river. Adults were captured from May through August.
Locality data. CANADA: Alberta: Waterton Lakes National Park, Cameron Lake, 5450 ', 4.VIII.1976 Comments. We have tentatively included the females from New Brunswick as belonging to this species. The difference in body colour, the slightly different shape of pronotum and the temples of the head in the New Brunswick and western specimens we attribute to infraspecific variations because the shape of spermatheca and the tergites and sternite VIII are similar in females of both populations. The study of males from New Brunswick is critical to confirm our identification. The specimens from the north usually are darker than the specimens from more southern localities in many species of aleocharines. Gnathusa caribou Lohse, in Lohse et al. 1990: 146;Klimaszewski et al. 2011: 55. Diagnosis. Body length 2.8-3.6 mm, sides narrowly subparallel; body colour dark brown to almost black, with antennae bright yellow and tarsi rust-brown to yellowish; integumental microsculpture dense and surface strongly glossy; head round, about the same size as the pronotum, labrum lacking stout spines but with fine setae of unequal length; pronotum small, transverse, angular, slightly narrower than elytra; elytra at suture subequal in length to pronotum; abdomen subparallel; antennal articles 6-10 subquadrate to slightly transverse, last article short and broadly oval (Fig. 3a). MALE: tergite VIII widely truncate apically (Fig. 3c); sternite VIII slightly pointed at apex (Fig. 3d); median lobe of aedeagus with tubus almost straight and apex pointed ventrally in lateral view (Fig. 3b). FEMALE: tergite VIII truncate apically (Fig. 1f); sternite VIII rounded apically (Fig. 3g); spermatheca pipe-shaped, with spherical capsule and long and straight stem, neck well sclerotized (Fig. 3e).

Gnathusa caribou
Distribution. This native Nearctic species is known in Canada from the Northwest Territories and Yukon Territory (Map 2), and from Alaska (Lohse et al. 1990).
Bionomics. Adults were captured from June to July in tundra by sifting organic litter under Salix, moss, and a pile of leaves stored by a rodent. Diagnosis. Body length 3.0-3.4 mm, sides subparallel; body colour dark brown, with tarsi lighter and antennae brown and often with reddish tinge; head round and almost as wide as pronotum or at most as wide as pronotum, equal in size to pronotum; pronotum transverse, angular, about as wide as maximum width of elytra; abdomen subparallel, at base as wide as elytra, widest in apical half; antennal articles 5-10 quadrate to slightly transverse (Fig. 4a). MALE: tergite VIII pointed apically (Fig. 4c); sternite VIII slightly pointed at apex (Fig. 4d); median lobe of aedeagus with tubus strongly produced ventrally in lateral view, apex pointed (Fig. 4b). FEMALE: tergite VIII truncate apically (Fig. 4f); sternite VIII rounded apically (Fig. 4g); spermatheca pipe-shaped, with small spherical capsule and long, thin and almost straight stem (Fig. 4e).
Distribution. This native Nearctic species is known only from Labrador (Map 3).

Key to Canadian species of Mniusa
New provincial and territorial records are indicated in boldface font.
Distribution. This native Nearctic species was described from Newfoundland and is herein recorded for the first time from New Brunswick (Map 3).
Bionomics. Adults were collected from May to July using pitfall traps in an old boreal balsam fir forest in Newfoundland; by sifting moss near a brook, sifting deep con ifer litter at base of large red spruce in a mature red spruce forest, and from Lindgren funnel traps in a rich Appalachian hardwood forest in New Brunswick.  Ocyusa yukonensis Klimaszewski & Godin, in Klimaszewski et al. 2012: 218. Diagnosis. Body length 2.8-3.0 mm, narrowly elongate and broadest at elytra; body dark brown to almost black, sometimes with reddish tinge on elytra, reddish-brown antennae and legs; forebody with dense microsculpture, dense punctation and pubescence, and strongly glossy; head round and narrower than pronotum; pronotum transverse, with sides strongly arcuate and narrowed anteriad, slightly narrower than elytra; elytra at suture about as long as pronotum or slightly longer (Fig. 6a); abdomen broadly arcuate laterally, slightly narrower than elytra and with basal impressions on first three visible tergites; antennal articles V-X slightly transverse (Fig. 6a). MALE: male tergite VIII truncate apically (Fig. 6c); sternite VIII rounded apically and slightly produced medially (Fig. 6d); median lobe of aedeagus with tubus straight and slightly produced ventrally and with complex structures of internal sac (Fig. 6b). FEMALE: tergite VIII truncate apically with slightly acute lateral angles (Fig. 6f); sternite VIII rounded apically and slightly produced apically (Fig. 6g); spermatheca with narrowly elongate sac-shaped capsule connected with L-shaped neck and narrow and long stem (Fig. 6e).
Distribution. This native Nearctic species was recently described from the Yukon Territory , and is here newly reported from Nova Scotia, New Brunswick, Quebec, and British Columbia, which constitute new provincial records (Map 6).

Mniusa odelli
Distribution. This native Nearctic species is here described from Nova Scotia, New Brunswick, and Quebec (Map 5).
Bionomics. Adults were collected from May to July in Lindgren traps in an oldgrowth eastern hemlock stand, an old hardwood stand, and in a sugar maple forest and a red spruce forest.
Etymology. This species is named after Odell Park in Fredericton, New Brunswick, where the holotype was found. This park was originally the estate of Reverend Jonathan Odell whom the park was named after. This park was established in 1954.
Other locality data [specimens in poor condition and tentatively identified as this species].

Key to Canadian species of Ocyusa
Distribution. This native Nearctic species is known from Alaska, Yukon Territory and Ontario (Brunke et al. 2012), and is here newly reported from the island of Newfoundland and New Brunswick [new provincial records] (Map 4).
Bionomics. Some adults were collected from June to July at lake margins, on moist soil/gravel among sedges and by treading Carex and grasses.   Webster et al. 2009: 192. Ocyusa brevipennis Bernhauer 1906: 344. Moore and Legner 1975 confirmed.
Diagnosis. Body length 2.8-3.0 mm, sides subparallel; body colour dark brown, with tarsi, two basal antennal articles and legs rust-brown, rest of antennal articles dark brown; forebody with moderately dense microsculpture, punctation and pubescence, and strongly glossy; head round and about as wide as pronotum; pronotum transverse, with sides strongly arcuate, widest in apical third, and as wide as elytra; elytra at suture much shorter than pronotum (Fig. 9a); abdomen broadly arcuate laterally, slightly broader than elytra at middle and with basal impressions on first three visible tergites; antennae with articles V-X subquadrate (Fig. 9a). MALE: male tergite VIII with apical margin slightly pointed medially (Fig. 9c); sternite VIII rounded apically (Fig. 9d); median lobe of aedeagus with tubus convex basally and then strongly bent ventrally and with complex structures of the internal sac (Fig. 9b). FEMALE: tergite VIII truncate apically with small projections laterally (Fig. 9f); sternite VIII rounded apically (Fig. 9g); spermatheca with small spherical capsule with long and broad invagination, and S-shaped broad stem slightly swollen posteriorly (Fig. 9e).
Distribution. This native Nearctic species was described from Rhode Island by Casey 1894 [often cited as 1893]. It was recorded also from New Brunswick in Canada (Map 5) and from Iowa and Massachusetts in the United States (Casey 1894, Bernhauer 1906, Moore andLegner 1975, Webster et al. 2009).
Bionomics. Some adults were collected from April to July at lake margins, on moist soil/gravel among sedges, and by treading emergent Carex and grasses. Webster et al. (2009) collected adults by sifting grass litter and mosses (usually sphagnum) near small pools in eastern white-cedar swamps, red maple (Acer rubrum L.) swamps with eastern white-cedar, and in alder swamps. Others were collected by treading green sphagnum, Carex, and grasses in a black spruce bog and by treading cattails and sedges in a boggy marsh. Locality