Atheta (Microdota) subtilis (Scriba)

Klimaszewski, Jan, Webster, Reginald P., Sikes, Derek, Bourdon, Caroline & Labrecque, Myriam, 2015, A review of Canadian and Alaskan species of the genera Clusiota Casey and AthetaThomson, subgenusMicrodota Mulsant & Rey (Coleoptera, Staphylinidae, Aleocharinae), ZooKeys 524, pp. 103-136 : 109

Taxon classification Animalia Coleoptera Staphylinidae

Atheta (Microdota) subtilis (Scriba) Figs 1-8

Homalota subtilis Scriba 1866: 128. As Atheta (Microdota) : Brundin 1948, Palm 1970, Benick and Lohse 1974, Smetana 2004 (review of literature and description).

Material examined.

Canada, Labrador, Goose Bay, Rts. 500 and 520 jct., 53° 16.9 N, 60° 24.6 W, 13-26.VIII.2001, S. and J. Peck, Flight Intercept Trap, elevation 10 m, spruce-poplar forest (LFC) 3 females, 1 male; Goose Bay, Goose River Bridge, 53° 22.2 N, 60° 26.2 W, 15-20.VIII.2001, S. and J. Peck, elevation 10 m, spruce-birch forest (LFC) 1 male. New Brunswick, Albert Co., Caledonia Gorge P.N.A., 45.7941°N, 64.7736°W, 13.IX.2011, R.P. Webster // near Crooked Creek, mixed forest (red spruce and yellow birch) in decaying gilled mushrooms (RWC) 1 male; Carleton Co., Wakefield, Meduxnekeag Valley Nature Preserve, 46.1940°N, 67.6800°W, 3.VII.2006, R.P. Webster coll. // mixed forest on Pleurotus sp. on dead standing Populus tremuloides (RWC) 1 male; York Co., New Maryland, Charters Settlement, 45.8331°N, 66.7410°W, 27.VII.2005, R.P. Webster coll. // mixed forest on flowers of Spiraea alba (LFC) 1 male; Restigouche Co., off Bellone Road, 47.7755°N, 68.2501°W, 24.VIII.2011, R. Webster and M. Turgeon // Old spruce and fir forest, mossy forest floor, in gilled mushrooms in various stages of decay (RWC) 1 female.

Diagnosis.

Body length 1.5−2.0 mm, subparallel, flattened, reddish brown to dark brown, head and abdomen darker than pronotum and elytra in some specimens, legs yellowish brown (Fig. 1); integument moderately glossy, densely punctate and densely pubescent on forebody and less so on abdomen, microsculpture fine; head slightly narrower than pronotum, strongly narrowed posteriad, eyes large and about as long as postocular area dorsally; pronotum transverse, narrower than elytra; elytra wider and longer than pronotum; abdomen subparallel. MALE. Tergite VIII truncate apically (Fig. 2); sternite VIII broadly rounded apically (Fig. 3); median lobe of aedeagus narrow, and strongly ventrally produced apically in lateral view (Fig. 4); internal sac structures complex (Figs 4, 5). FEMALE. Tergite VIII broadly emarginated apically (Fig. 6); sternite VIII slightly emarginated apically (Fig. 7); spermatheca L-shaped with long, broad sac-shaped capsule bearing wide and shallow apical invagination and club-shaped short and swollen apically stem (Fig. 8).

Natural history.

The LB specimens were collected in flight intercept traps set in spruce-poplar forest. The NB specimens were found in gilled mushrooms at various stages of decay in spruce/fir forest, in Pleurotus sp. on dead standing Populus tremuloides , in mixed forest on flowers of Spiraea alba , and in a mixed forest with red spruce and yellow birch. Adults were captured from July to September.

Distribution.

Atheta (Microdota) subtilis is a Palaearctic species (for details, see Brundin 1948, Palm 1970, Benick and Lohse 1974, Smetana 2004), and it is reported here as adventive for the first time from Canada (LB, NB) and North America.

Comments.

Adults of Atheta subtilis from LB were captured in association with Atheta pseudosubtilis Klimaszewski and Langor. Some females of the former species, because of similarly shaped spermatheca and poorly preserved body, were misidentified as the latter species. We have compared European specimens of Atheta subtilis with those from Canada (LB, NB) and found no significant differences in external morphology and shape and structures of genitalia.