Lathrobium (Lathrobium) islae 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 (Lathrobium) islae Haberski & Caterino sp. nov.

Type material.

Holotype ♂ (FMNH): "USA: NC: Caldwell Co., 36.1117°N, 81.8068°W, Grandfather Mountain, Calloway Peak X.6.2020, M. Caterino, F. Etzler, A. Haberski, sifted litter." / "Caterino DNA voucher, Ext. MSC-6239" / "CLEMSON ENT [QR CODE] CUAC000169030". Paratypes (36, CUAC, FMNH, VMNH): 10: same locality as type, 36.1118°N, 81.8105°W, x.06.2020 (CUAC000112914, CUAC000112915, CUAC000177130, CUAC000177131, CUAC000177132, CUAC000177133, CUAC000177134, CUAC000177135, CUAC000177136, CUAC000177137); 3: same locality as type, 36.0978°N, 81.8293°W, 5370ft., iv.21.2022 (CUAC000177093, CUAC000177094, CUAC000177095); 1: same locality as type, 36.1118°N, 81.8112°W, x.06.2020 (CUAC000177109); 20: same locality as type, 36.1117°N, 81.8088°W, x.06.2020 (CUAC000177110, CUAC000177111, CUAC000177112, CUAC000177113, CUAC000177114, CUAC000177115, CUAC000177116, CUAC000177117, CUAC000177118, CUAC000177119, CUAC000177120, CUAC000177121, CUAC000177122, CUAC000177123, CUAC000177124, CUAC000177125, CUAC000177126, CUAC000177127, CUAC000177128, CUAC000177129); 1: same locality as type, 36.1104°N, 81.8046°W, v.17.2021 (CUAC000177138); 1: same locality as type, 36.1116°N, 81.8117°W, V.17.2021 (CUAC000135036).

Other material.

North Carolina : Mitchell Co.: Grassy Ridge Bald, 6135', (36.0985, -82.1791), M.S. Caterino, 08 Jun 2020 (CUAC); Mitchell Co. : Roan High Bluff, 6225-6251', (36.0931, -82.1453), M.S. Caterino, 15 Aug 2018 (3, CUAC); Mitchell Co. : Roan High Knob, 5756-6286', (36.1045, -82.1224), M.S. Caterino, 08 Jun 2020 (3, CUAC). Virginia: Smyth Co. : Mt. Rogers , 5699', Jefferson National Forest (36.6602, -81.5447), M.S. Caterino & P. Marek, 03 Jul 2018 (7, CUAC); Smyth Co. : Mt. Rogers , 5699', Jefferson National Forest (36.6602, -81.5447), M.S. Caterino & P. Marek, 03 Jul 2018, CUAC000187893, CUAC000187899 (15 larvae, CUAC); Smyth Co. : Mt. Rogers , 5666-5680', Jefferson National Forest (36.6605, -81.5447), M.S. Caterino & F. Etzler, A. Haberski, 27 Oct 2020 (27, CUAC); Smyth Co. : Mt. Rogers , 5686', Jefferson National Forest (36.6612, -81.5456), M.S. Caterino, 27 Oct 2020 (3, CUAC); Smyth Co. : Mt. Rogers , Jefferson National Forest (36.657, -81.555), C.W. Harden, 15 Apr 2019 (CUAC); Smyth Co. : Whitetop Mountain , 5503', Jefferson National Forest (36.6391, -81.6064), M.S. Caterino & P. Marek, 03 Jul 2018 (CUAC); Smyth Co. : Whitetop Mountain , 5436', Jefferson National Forest (36.6379, -81.6053), M.S. Caterino, 27 Oct 2020 (CUAC); Smyth Co. : Whitetop Mountain , Jefferson National Forest (36.629, -81.596), C.W. Harden, 15 Apr 2019 (CUAC); Grayson Co. : Wilburn Ridge , 5450', Jefferson National Forest (36.6525, -81.5167), M.S. Caterino & P. Marek, 03 Jul 2018 (2, CUAC) .

Diagnosis.

This species can be distinguished from the closely related L. lividum only by its genitalia. The spines of the internal sac of their aedeagi differ conspicuously (Fig. 7E, F vs Fig. 8D, E ). Differences in female genitalia are more subtle, but the gonocoxites of L. islae are narrower at their base. No intermediate forms are known.

Four other species of Nearctic Lathrobium have short elytra and functional eyes, but none are likely to be mistaken for L. islae or L. lividum . Lathrobium brevipenne , L. carolinae , and L. camplyacra are twice as large, lighter in color, and have an overall different gestalt. Lathrobium pallescens has a pale red body color and its eyes are much smaller, 1/8 the lateral length of the head with ~ 30 ommatidia.

Description.

Habitus (Fig. 7A ). Small species, total body length ~ 4.5 mm long, FL 2.5-3.0 mm long. Coloration: body black; legs, palpomeres, and antennae dark red.

Head subquadrate, as wide as long, widest posteriorly and narrower anterior to eyes; posterior angles slightly rounded; epicranium coarsely punctate, 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 the eyes, laterally posterior to the eyes, and above the mandible insertions; gular sutures arcuate, widely separate, 1/16 width of head apart at their most proximal point; neck ½ as wide as head. Eyes large and well developed with ~ 95 ommatidia, occupying ¼ lateral length of the head. Antennae moniliform, as long as head and pronotum combined; scape as long as antennomeres II and III combined; antennomeres II-IV elongate, gradually widening so that antennomeres V-IX are as wide as long; apical antennomere longer, subacute.

Pronotum longer than wide, as wide or slightly wider than head; sides parallel; angles rounded; punctures large, spaced one diameter apart, impunctate at midline with a visible line; interstices shiny with a finely punctate microsculpture. Elytra shorter but slightly wider than pronotum, as wide as head, as long as wide; anterior angles somewhat squared, posterior margins sinuate; scutellum round; punctures small, irregularly spaced, most 1-2 × their diameter apart; interstices with finely punctate microsculpture. Hindwings vestigial, 0.2 mm long, 1/5 length of elytra. Posterior margin of abdominal tergite VII without palisade fringe.

♂: Sternite VII flattened medially with shallow notch on the posterior margin; posterior margin of sternite VIII with a deep U-shaped notch (Fig. 7D ). Aedeagus 1.7 mm long (Fig. 7E, F ), ventral process short, not extending much beyond the median foramen posteriorly, lightly sclerotized portion of the median lobe protruding beyond it in lateral view; dorsal plate asymmetrical; internal sac with a single large spine with a characteristic club tip in ventral view.

♀: Sternite VIII slightly oblong with a triangular patch of dense setae at the tip (Fig. 7C ); paraprocts divided anteriorly; proctiger conical. sternum IX with valvifers and coxites fused, valvifers narrow at base (Fig. 7B ); subgenital plate absent.

First instar larva: Body elongate, ~ 3 mm long; well sclerotized (Fig. 41A ); head, thoracic, and abdominal tergites brown, appendages light yellow, intersegmental membrane white, translucent.

Head ovate, widest at stemmata and slightly tapered posteriad (in dorsal view), dorsoventrally flattened, 1.1 × as long as wide, dorsal setae as in Fig. 41A ; head 2.5 × wider than neck, dorsal ecdysial lines bifurcate 1/2 distance between neck and nasale margin; six stemmata present, arranged as in Fig. 41B ; anterior margin of nasale (Fig. 41C ) with nine blunt teeth pointing anteriorly, one quadrate median tooth with tetradentate anterior edge, a pair of paramedian teeth, and three pairs of lateral teeth; the innermost lateral teeth are small and indistinct; paramedian and lateral teeth armed with nodular setae, and a pair of nodular setae separate median and paramedian teeth; Apotome of gula not reaching tentoral pits.

Antennae (Fig. 41F ) length ratio: 1.0:2:3.1:1.6; antennomere I triangular; antennomere II with two pores; antennomere III with three elongate macrosetae, three solenidia, one pore; antennomere IV club-shaped with apical solenidia; sensory appendage 0.9 × as long as antennomere IV.

Mandibles (Fig. 41D ) long, falciform, serrate along inner margin, with a single seta near the base on the outer ventral edge. Maxilla (Fig. 41D ) with cardo triangular, widening from base to apex; stipes quadrate, 1.3 × longer than cardo; mala digitiform, tapering toward apex, 0.9 × as long as palpomere I, with apical sensory appendages and two pores; palpifer with one seta. Maxillary palpomere length ratios: 1.0:1.2:2.8; palpomere II with two setae; palpomere III with one basal sensory appendage and numerous small apical appendages. Labium with prementum subquadrate, basal portion strongly sclerotized; ligula with elongate membranous apex, twice as long as wide, densely fimbriate, separated from prementum by a distinctly sclerotized transverse strip; palpomere I 1.6 × as long as II; palpomere II bearing short sensilla at apex.

Dorsal sclerites of thorax with ecdysial lines along midline of body; prothorax subquadrate, narrowing slightly anteriorly, chaetotaxy as in Fig. 41A ; thoracic tergite II and III subequal; abdominal sclerites well sclerotized, with two small pleural sclerites per segment on each side; basal segment of urogomphus 2.6 × as long as terminal segment, with seven prominent lateral setae; terminal segment of urogomphus slender, with one short and one long apical seta.

Second instar larva: Second instar (Fig. 42A ) resembles first, except as follows. Body larger, ~ 6 mm long. Head subquadrate; dorsal ecdysial lines of the head bifurcate 2/5 distance between nasale margin and neck; median tooth of nasale triangular with serrated edges and a blunt tip (Fig. 42C ). Apotome of gula reaching tentoral pits. Antenna (Fig. 42F ) length ratios: 1.0:3.5:2.8:1.5; antennomere IV club-shaped with apex 2 × as wide as base. Mandible interior margin smooth (Fig. 42D ). Maxilla palpomere length ratios: 1.0:1.5:3.3; Labial palpomere I 1.5 × II (Fig. 42E ); palpomere I distinctly curved; palpomere II bent near apex. Prothorax round. Urogomphi broken off of only known specimen.

Etymology.

Named in honor of Isla Haberski, daughter of the first author, who was born during the preparation of this manuscript.

Distribution and ecology.

Lathrobium islae inhabits spruce-fir forests above 1500 m in the Grayson Highlands, Roan Highlands, and on Grandfather Mountain (Fig. 43 ). It can be collected from leaf litter but is most common on boulders beneath bryophyte mats. It has not been found in spruce-fir forests south of the French Broad River basin, where its microhabitat is inhabited by L. smokiense and L. balsamense . Adults collected Jul-Sep. Larvae collected Mar-Jul.

Remarks.

Lathrobium islae was not monophyletic in our COI phylogeny and ASAP identified five genetic partitions. Given this degree of genetic variation, populations outside the type locality might also differ in minor ways morphologically, perhaps in characters not yet evaluated. Larvae were associated with adults by DNA barcoding.

Figures

Figure 7. Lathrobium islae 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 8. Lathrobium lividum 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 41. Lathrobium islae first instar larva A habitus B head in lateral view C nasale D mandible E maxilla F antenna. Scale bars: 1 mm (A); 500 μm (B); 100 μm (B, D); 250 μm (E, F).

Figure 42. Lathrobium islae second instar larva A habitus B head in lateral view C nasale D mandible E maxilla F antenna. Scale bars: 1 mm (A, B); 250 μm (C); 500 μm (D, E, F).

Figure 43. Distribution of Lathrobium islae (circle), L. lividum (star).