Geostiba (Sibiota) bicarinata Lohse & Smetana 1988, sp. n.
Creators: name: Gusarov, Vladimir I.
Publisher: name: Zenodo
Year: 2002
Subjects: Biodiversity
Taxonomy

description: 2. Geostiba (Sibiota) bicarinata Lohse & Smetana, 1988 (Figs. 51­71)
Geostiba bicarinata Lohse & Smetana, 1988: 273, ex parte. Geostiba bicarinata: Pace, 1997: 104.
Type material. Holotype,, UNITED STATES: North Carolina: Haywood Co.: Richland Balsam Mt. [35°22'01"N 82°59'26"W], 1860­1950 m (A.Smetana), 27.v.1986 (CNCI); allotype,, ditto; paratypes: 5, 3, ditto; 4,, ditto but 1850­1950 m, 25.v.1986 (all ­ CNCI).
Some paratypes of G. bicarinata belong to other species: Geostiba pluvigena Gusarov, sp. n.:, North Carolina: Haywood Co., Blue Ridge Parkway, Browning Knob Mt., 1830­1890 m (A.Smetana), 28.v.1986 (examined) (CNCI). Two other paratypes were not found in CNCI, but their locality data are listed by Lohse and Smetana (1988: 275). My collecting efforts demonstrated that these paratypes originate from the mountain massifs were G. bicarinata does not occur. These presumably misidentified paratypes belong to G. alticola (one specimen, Buncombe Co.: base of Mt. Mitchell at Blue Ridge Parkway, about 1650 m (A.Smetana), 3.vi.1986) and G. nimbicola (one specimen, Great Smoky Mountains National Park, Clingmans Dome, 1950­2020 m, (A.Smetana) 2.vi.1986).
Additional material. UNITED STATES: North Carolina: Haywood Co.: 2, Richland Balsam Mt., 1829m (J.F. Cornell), fir duff, 26.iv.1974 (KSEM); Haywood Co. / Jackson Co.: 15 specimens, Richland Balsam Mt., near summit, 14 km S Waynesville, 35°22.50'N 82°59.43'W, 1950 m, in forest litter, Picea rubens, Abies fraseri, Vaccinium (V.I.Gusarov), 3.vi.2001; 12 specimens, ditto but W slope of Richland Balsam Mt., 35°22.28'N 82°59.42'W, 1900 m, Picea rubens, Abies fraseri; 15 specimens, ditto but S slope of Richland Balsam Mt., 35°21.04'N 82°59.56'W, 1850 m, Picea rubens, Abies fraseri, Betula, Oxalis; 14 specimens, Blue Ridge Parkway, 11 km SSW Waynesville, 35°23.3'N 83°02.43'W, 1800 m, in forest litter, Picea rubens, Abies fraseri, Betula, Oxalis (V.I.Gusarov), 2.vi.2001; 10 specimens, ditto but 13 km S Waynesville, 35°22.12'N 82°59.65'W, 1800 m, in forest litter, Picea rubens, Abies fraseri, Oxalis (V.I.Gusarov), 3.vi.2001 (all – KSEM and SPSU);, Blue Ridge Parkway, Grassy Ridge Mine Overlook, 8 km SSW Waynesville, 35°24.94'N 83°02.80'W, 1650 m, in forest litter, Tsuga, Quercus, Betula (V.I.Gusarov), 2.vi.2001; Haywood Co. / Buncombe Co.:, Little Pisgah Mt., near summit, 35°25.48'N 82°45.51'W, 1730­1760 m, in forest litter, Fagus, Quercus, Rhododendron (V.I.Gusarov), 20.ix.2001 (all – SPSU).
Diagnosis. Geostiba bicarinata can be distinguished from other Nearctic species of Geostiba by having small eyes (temple length to eye length ratio 3.8­5.0), 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 male abdominal tergum 7 in front of posterior margin, the shape of the aedeagus (Figs. 57­64, 66­71) and the shape of the spermatheca (Fig. 65).
Geostiba bicarinata is closely related to G. graveyardensis but differs in the following: the apex of median lobe in lateral view not bent ventrally (Figs. 59­60, 79­80), in ventral view without apical process (Figs. 57­58, 77­78).
Description. Length 2.0­ 2.3 mm. Dark brown, elytra often lighter, antennae brown, legs and mouthparts yellowish brown. 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 3.8­5.0. Antennal article 2 longer than article 3, article 4 slightly transverse, 5­10 transverse, last article as long as 9 and 10 combined (as in Fig. 16).
Pronotum slightly transverse, width 0.4­0.46 mm, width to length ratio 1.1, 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 3­7 times their diameter. Tergum 7 without white edge.
In males pronotum slightly flattened on disc. Male tergum 7 with two medial carinae in front of posterior margin. Male tergum 8 with two or four weak and short carinae in front of posterior margin, and two weak projections at posterior margin (Fig. 51). Male sternum 8 with convex posterior margin (Fig. 52).
Female tergum 8 with slightly convex posterior margin (Fig. 53), posterior margin of sternum 8 slightly concave medially (Figs. 54­55).
Aedeagus as in Figs. 57­64, 66­71. Apex of median lobe in ventral view broad, with convex outline, without apical process (Figs. 57­58), in lateral view not bent ventrally (Figs. 59­60), distal diverticula of internal sac with numerous denticles (Figs. 61, 64, 70), in ventral view narrow (Fig. 64), in lateral view broad (Fig. 70).
Spermatheca as in Fig. 65.
Distribution. Known from the Great Balsam Mountains and Little Pisgah Mountain (North Carolina) (Figs. 338, 340).
Natural History. Geostiba bicarinata was collected by sifting forest litter at altitudes above 1600 m mostly in pure conifer or mixed forest with red spruce (Picea rubens) and Fraser’s fir (Abies fraseri).
description: Published as part of Gusarov, Vladimir I., 2002, A revision of Nearctic species of the genus Geostiba Thomson, 1858 (Coleoptera: Staphylinidae: Aleocharinae), pp. 1-88 in Zootaxa 81 on pages 24-28, DOI: 10.5281/zenodo.155701