Lathrobium (Abletobium) balsamense Haberski & Caterino, 2024

Haberski, Adam & Caterino, Michael S., 2024, A review of Nearctic Lathrobium (Coleoptera, Staphylinidae), with revision and descriptions of new flightless species from the mountains of the southeastern U. S., ZooKeys 1198, pp. 193-277 : 193

Lathrobium (Abletobium) balsamense Haberski & Caterino sp. nov.

Type material.

Holotype ♂ (FMNH): "USA: NC: Haywood Co., 35.3632°N, 82.9885°W, Richland Balsam Mountain, 6180', IX.11.2019, Sifted Litter, M. Caterino." / Caterino DNA voucher, Ext. MSC-4413, Morphosp RB.B.320" / "CLEMSON ENT [QR CODE] CUAC000003949". Paratypes (4, CUAC, FMNH): 2: same locality as type, 35.3627°N, 82.9885°W, IX.11.2019 (CUAC000003627, CUAC000177150); same locality as type, 35.3630°N, 82.9890°W, 6200ft, v.08.2018 (CUAC000177151); same locality as type, 35.3676, -82.9902, 6398', v.8.2018 (CUAC000048512).

Other material.

North Carolina : Jackson Co.: Balsam Mountain Preserve , Nantahala National Forest , (35.3751, -83.0981), S. Myers, 15 Jun 2015 (CUAC); Haywood Co. : Mt. Lyn Lowry , 6205' (35.4640, -83.1100), M.S. Caterino, 22 Sep 2020 (2, CUAC); Haywood Co. : Mt. Lyn Lowry , 6192-6203' (35.4640, -83.1101), M.S. Caterino, 15 Apr 2021 (9, CUAC); Haywood Co. : Mt. Lyn Lowry , 6200' (35.4638, -83.1108), M.S. Caterino, 22 Apr 2020 (3, CUAC); Haywood Co. : Richland Balsam, 6398', Blue Ridge Parkway (35.3676, -82.9902), M.S. Caterino, 8 May 2018 (USNM); Haywood Co. : Richland Balsam, 6069-6397', Blue Ridge Parkway, A. Smetana, 25 May 1986 (CNC); Haywood Co. : Waterrock Knob, 6275', Blue Ridge Parkway (35.4643, -83.1374), M.S. Caterino, 29 May 2018 (4, CUAC); Haywood Co. : Waterrock Overlook, 5800', Blue Ridge Parkway, J.M. & B.A. Campbell, 1 Sep 1967 (4, CNC); Haywood Co. : Browning Knob, 6003-6200', Blue Ridge Parkway, A. Smetana, 28 May 1986 (CNC); Haywood Co. : Browning Knob, 6140', Blue Ridge Parkway (35.4630, -83.1310), 22 Sep 2020, M.S. Caterino (7, CUAC); Haywood Co.: Browning Knob, 6200-6220', Blue Ridge Parkway (35.4633, -83.1315), 22 Sep 2020 M.S. Caterino, A. Haberski (5, CUAC) .

Diagnosis.

This species can be distinguished from its close relative, L. smokiense , only by their aedeagi. In L. smokiense , the entire aedeagus is well sclerotized, whereas the aedeagus of L. balsamense is more typical for the genus with a distinct ventral process (Fig. 9E, F vs Fig. 10D, E ). Females can only be identified by geography, association with males, or DNA.

One other microphthalmous species, L. shermani Fall, 1917, occurs above 1000 m elevation in the southern Appalachians, although their ranges do not overlap. Adults are similar in size and appearance but are distinguished by the sexual characters. Males of L. balsamense lack a conspicuous comb of thick black setae on sternite VIII and has no spines on the internal sac of the aedeagus. In females, the gonocoxites lack the pubescence of L. shermani in the lower half.

Description.

Habitus (Fig. 9A ). Small species, total body length ~ 6 mm long, FL 2.6-2.8 mm long. Coloration: body reddish becoming lighter towards posterior segments of abdomen; legs, palpomeres, and antennae a paler reddish yellow.

Head subquadrate, posterior angles rounded; epicranium coarsely punctate with punctures less dense in median dorsal and anterior regions; interstices with strong transversely reticulate microsculpture throughout; head setose throughout, with long macrosetae projecting at posterior corners of head, corners of eyes, laterally posterior to eyes, and above mandible insertions; gular sutures straight and widely separated, 1/8 width of head but narrowing slightly posteriorly; neck 1/2 as wide as head. Eyes reduced to small white membranes without ommatidia, occupying 1/9 length of head. Antennae moniliform, as long as head and pronotum combined; scape as long as antennomeres II and III combined; antennomeres II-IV obconic and elongate, gradually widening so that antennomeres V-IX are as wide as long; apical antennomere longer, subacute.

Pronotum longer than wide, narrower than head and elytra; widest at anterior angles and tapering slightly posteriorly; anterior angles round, posterior angles less so; punctures small, spaced 1-2 × their diameter apart, impunctate at midline; interstices shiny with no microsculpture. Elytra shorter than pronotum, as wide as head, approximately as long as wide; posterior margin slightly sinuate; punctures large and shallow with indistinct edges, irregularly spaced, most approximately one diameter apart; setae angled to posterior; interstices with finely punctate microsculpture. Hindwings vestigial, 0.2 mm long, 1/4 length of elytra. Posterior margin of abdominal tergite VII without palisade fringe.

♂: Posterior margin of sternite VIII with a shallow U-shaped notch (Fig. 10C ). Aedeagus 1.1 mm long (Fig. 10E, F ), ventral process long, broad, and symmetrical, tapering to a blunt tip; dorsal plate long and situated dorsally; internal sac without spines.

♀: Sternite VIII conical (Fig. 9B ); paraprocts undivided anteriorly, apices as long as basal portion; proctiger conical; sternum IX with coxites and valvifers fused, basal half glabrous (Fig. 9B ); subgenital plate absent.

Etymology.

This species is named for the Plott Balsam and Great Balsam Mountains.

Distribution and ecology.

Lathrobium balsamense inhabits spruce-fir forests above 1500 m in the Great Balsam Mountains and Plott Balsam Mountains (Fig. 13 ) but is absent from the Great Smoky Mountains where the closely related L. smokiense occurs. It does not occur in spruce-fir forests north of the French Broad River basin, where its microhabitat is inhabited by L. lividum and L. islae . It can be collected from leaf litter but is most common beneath bryophyte mats on boulders. Collected May-Sep.

Figures

Figure 9. Lathrobium smokiense A habitus B female terminalia C female sternite VIII D male sternite VIII E aedeagus in ventral view F aedeagus in lateral view. Scale bars: 1 mm.

Figure 10. Lathrobium balsamense A female terminalia B female sternite VIII C male sternite VIII D aedeagus in ventral view E aedeagus in lateral view. Scale bars: 1 mm.

Figure 13. Distribution of Lathrobium absconditum (triangle), L. Lathrobium balsamense (square), L. hardeni (star), L. smokiense (circle).