Geostiba (Sibiota) nebuligena Gusarov, sp. n.

6. Geostiba (Sibiota) nebuligena Gusarov, sp. n. (Figs. 146­168)

Type material. Holotype,, UNITED STATES: Tennessee / North Carolina: Sevier Co. / Swain Co.: Appalachian Scenic Trail W of Clingmans Dome, 16 km S Gatlinburg, 35°33.93'N 83°31.76'W, 1800 m, in forest litter, Picea, Abies, Acer, Fraxinus, Oxalis (V.I.Gusarov), 22.vi.2001 (KSEM).

Paratypes: UNITED STATES: Tennessee / North Carolina: Sevier Co. / Swain Co.: 49 specimens, same data as the holotype (KSEM, AMNH, CNCI, SPSU, FMNH); 27 specimens, Clingmans Dome [35°33'46"N 83°29'55"W] (J.S. & A.K.Ashe), 31.vii.1991 (KSEM); 2, ditto but 2000 m, Fraser Fir – Red Spruce forest (J.Bengston), 7.vii.1974 (FMNH); 83 specimens, Clingmans Dome Road, 14 km SSE Gatlinburg, 35°35.46'N 83°28.28'W, 1800 m, in forest litter, Picea rubens, Abies fraseri, Oxalis, Rubus (V.I.Gusarov), 1.vi.2001 (KSEM, SPSU); 19 specimens, Appalachian National Scenic Trail, W of Clingmans Dome, 16 km S Gatlinburg, 35°33.88'N 83°31.41'W, 1930 m, in forest litter, Picea, Abies, Betula, Oxalis (V.I.Gusarov), 22.vi.2001 (KSEM, SPSU); 2,, trail to Mt. Le Conte from Newfound Gap (W.S.Suter), 29.v.1982 (KSEM); 24 specimens, 0.5 km E Newfound Gap, 13 km SE Gatlinburg, 35°36.44'N 83°25.37'W, 1650 m, in forest litter, Picea rubens, Oxalis, Vaccinium (V.I.Gusarov), 1.vi.2001 (KSEM, SPSU); Tennessee: Sevier Co.: 13 specimens, Highway 441 & 71, 13 km SE Gatlinburg, 35°37.3'N 83°26.3'W, 1300 m, in forest litter, Rhododendron, Tsuga, Betula (V.I.Gusarov), 22.vi.2001 (SPSU);,, descending the Chimney Tops, 9­10 km SSE Gatlinburg, 35°37.6­38.2'N 83°28.2'W, 1040­1200 m, in forest litter, Tsuga, Acer, Rhododendron (V.I.Gusarov), 22.vi.2001 (SPSU);, Great Smokey Mts. National Park (W.Shear & F.Coyle), 24.x.1969 (FMNH); 18 specimens, Mt. Le Conte, half way up [35°38.5'N 83°26.8'W], deciduous forest, dry leaf litter near log (Lackey), 5.viii.1956 (FMNH, SPSU); North Carolina: Swain Co.:,, S slope of Clingmans Dome, 19 km NW Cherokee, 35°33.66'N 83°29.9'W, 2000 m, in forest litter, under young Abies trees (V.I.Gusarov), 1.vi.2001 (SPSU);

Mislabeled material. 14 specimens, UNITED STATES: Michigan, Gogebic Co., Ottawa National Forest, Sylvania Tract, litter & mycelium (J.Wagner), 13.viii.1977 (KSEM). These specimens are identical with the types of G. nebuligena in all external characters and in genitalia. G. nebuligena is a wingless species restricted to the Great Smoky Mountains massif in the Southern Appalachians, and it is impossible for this species to occur also in Michigan, the area which was covered by ice sheet in Pleistocene. I consider these 14 specimens as mislabeled and exclude them from the types series, because their origin is unknown. Geostiba nebuligena does not occur in Michigan.

Diagnosis. Geostiba nebuligena can be distinguished from other Nearctic species of Geostiba by having small eyes (temple length to eye length ratio 2.9­4.0), pronotal pubescence of type V, reduced wings, short elytra (pronotum length to elytron length ratio 1.3), the presence of two short parallel carinae in the middle of abdominal tergum 7 in front of posterior margin and the shape of the aedeagus (Figs. 152­161, 163­168) and the shape of the spermatheca (Fig. 162).

Geostiba nebuligena differs from closely related G. nimbicola, G. pluvigena and G. crepusculigena in having apex of median lobe with strong apical denticle (in lateral view) (Figs. 155­156, 102­103, 128­129, 176­177).

Description. Length 1.6­1.9 mm. Light brown to brown, antennae light brown, legs and mouthparts brownish yellow. Body parallel­sided.

Head as wide as long, surface on disk with fine isodiametric microsculpture, puncturation very fine, distance between punctures equal to 3­4 times their diameter. Temple length to eye length ratio 2.9­4.0. Antennal article 2 longer than article 3, article 4 transverse (width to length ratio 1.6), articles 5­10 strongly transverse, last article as long as 9 and 10 combined (as in Fig. 17).

Pronotum as wide as long, width 0.37­0.40 mm, wider than head (pronotal width to head width ratio 1.2); microsculpture and puncturation as on head. Pronotal pubescence of type V. Elytra measured from humeral angle shorter than pronotum (pronotal length to elytral length ratio 1.3), wider than long (1.5), with fine isodiametric microsculpture and fine asperate puncturation, distance between punctures equals 2­3 times their diameter.

Elytral suture behind scutellum slightly raised in both sexes. Wings reduced to short vestiges, shorter than elytra.

Abdominal terga with fine microsculpture of transverse meshes, with fine and sparse puncturation, puncturation becoming finer towards abdomen apex, on terga 3­5 distance between punctures equals 3­6 times their diameter. Tergum 7 without white edge.

Male tergum 7 with two medial carinae in front of posterior margin. Male tergum 8 with two weak and short carinae in front of posterior margin, posterior margin convex (Fig. 146). Male sternum 8 with convex posterior margin (Fig. 147).

Female tergum 8 with convex posterior margin (Fig. 148), sternum 8 with weakly emarginate posterior margin (Figs. 149­150).

Aedeagus as in Figs. 152­161, 163­168. Apex of median lobe in ventral view narrow, its outline doubly emarginate apically (Figs. 152­154), in lateral view strait, with strong apical denticle ventrally (Figs. 155­156), distal diverticula of internal sac in ventral view broad (Figs. 160­161).

Spermatheca as in Fig. 162.

Distribution. Known from the Great Smoky Mountains massif (Tennessee and North Carolina) (Figs. 338, 340).

Natural History. Geostiba nebuligena was collected at altitudes above 1000 m in leaf litter in pure conifer or mixed forest with red spruce (Picea rubens), Fraser’s fir (Abies fraseri) or hemlock.

Etymology. The specific name is derived from the Latin noun nebula (mist, fog) and the verb gigno (to be born, to arise). It refers to fogs in the Great Smoky Mountains where the species occurs.