A review of Nearctic Lathrobium (Coleoptera, Staphylinidae), with revision and descriptions of new flightless species from the mountains of the southeastern U. S. Author Haberski, Adam https://orcid.org/0000-0002-4062-178X Department of Plant & Environmental Sciences, Clemson University, Clemson, SC 29634 - 0310, USA ahaberski@gmail.com Author Caterino, Michael S. https://orcid.org/0000-0002-2597-5707 Department of Plant & Environmental Sciences, Clemson University, Clemson, SC 29634 - 0310, USA text ZooKeys 2024 2024-04-25 1198 193 277 http://dx.doi.org/10.3897/zookeys.1198.118355 journal article http://dx.doi.org/10.3897/zookeys.1198.118355 1313-2970-1198-193 59053839702C46C9B0F6AA37C61C0E45 0257BC4776C25532B6CEB2BDECD8E7AB Lathrobium (Abletobium) absconditum Haberski & Caterino sp. nov. Type material. Holotype ♂ (FMNH): "USA: VA: Bath Co., 38.0744°N , 79.6836°W , Dry Run Gorge, X.28.2018, C. Harden, oak-hickory woods; limestone gorge." / "CLEMSON ENT [QR CODE] CUAC000185176". Paratypes (3, CUAC, FMNH, VMNH): same data as holotype (CUAC000185174, CUAC000185175, CUAC000185177). Other material. Virginia: same data as holotype, CUAC000187891 ( 1 larva , CUAC); Highland Co. : Owl Cave , 2070', Water Sinks ( 38.2205 , -79.6046 ), C. Harden , 31 May-2 Aug 2019 (CUAC); Highland Co. : Water Sinks , 2080' ( 38.2211 , -79.6042 ), C. Harden , 4 May-31 May 2019 (VMNH) . Diagnosis. This species is larger than most microphthalmous Lathrobium known from Virginia and West Virginia. Males can be distinguished from most species by the lack of setal combs on sternite VIII and females by the presence of gonocoxite lobes. Lathrobium solum is of similar size and also lacks the transverse combs on sternite VIII. However, Lathrobium solum has transverse antennomeres V-VII, and more widely separated gular sutures. Aedeagi differ in the shape of their major spines, and L. solum has a characteristically shaped ventral process that reaches the dorsal plate in lateral view. The female of L. solum is unknown, so no distinctions can be made. Description. Habitus (Fig. 11A ). Large species, total body length ~ 9 mm long, FL 3.4-4.0 mm long. Coloration: body and appendages pale reddish. Head slightly wider than long, widest at posterior; posterior angles rounded. Epicranium coarsely punctate with punctures less dense in median dorsal portion; 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 (sulci) narrowing posteriorly until nearly touching; 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-IX obconic, longer than wide but become progressively wider; apical antennomere longer, subacute. Pronotum longer than wide, narrower than head and elytra; widest at anterior angles and tapering slightly posteriorly; all angles round, posterior angles less so; punctation is dense, punctures spaced one diameter apart, impunctate at midline with a faint line visible on posterior two thirds; interstices shiny with no microsculpture. Elytra distinctly shorter than pronotum, as wide as head, approximately as long as wide; posterior margin sinuate; punctures small and shallow with indistinct edges, irregularly spaced, most one diameter apart; setae angled to posterior; interstices with finely punctate microsculpture. Hindwings vestigial. Posterior margin of abdominal tergite VII without palisade fringe. Figure 11. Lathrobium absconditum 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. ♂: Larger, forebody 3.8-4.0 mm. Posterior margin of sternite VIII with broad but shallow emargination, patch of dense setae medially (Fig. 11D ). Aedeagus 1.5 mm long; ventral process long, narrow, and asymmetrical (Fig. 11E, F ); dorsal plate short and broad; internal sac with five spines, major spine long with two narrow asymmetrical processes. Figure 12. Lathrobium absconditum second instar larva A habitus B nasale C mandible D maxilla E antenna. Scale bars: 1 mm ( A, C ); 500 μm ( B, D, E ). ♀: Smaller, forebody 3.4 mm. Sternite VIII oblong, apex notched with micropubescence (Fig. 11C ); paraprocts undivided anteriorly, apices longer than basal portion; proctiger conical; sternum IX with coxites and valvifers fused (Fig. 11B ), base produced into distinct setose lobes; subgenital plate absent. Second instar larva : Body elongate, ~ 7 mm long; lightly sclerotized (Fig. 12A ), head more sclerotized; head and thoracic tergites light brown, legs and body white, translucent. Head ovate, tapered posteriad (in dorsal view), dorsoventrally flattened, 1.3 x as long as wide, with dorsal setae as in Fig. 12A ; head 3.6 x wider than neck; dorsal ecdysial lines bifurcate 2/5 distance between neck and nasale margin; stemmata absent; anterior margin of nasale (Fig. 12B ) as in L. hardeni , but median tooth triangular with edge serrated; Apotome of gula not reaching tentorial pits. Antennae (Fig. 12E ) length ratios: 1.0:3.8:2.9:1.7; 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 0.8 x as long as antennomere IV. Mandibles (Fig. 12C ) long, falciform, serrate along apical 1/3 of inner margin, with a single seta near base on outer ventral edge. Maxilla (Fig. 12D ) with cardo triangular; stipes elongate, 1.7 x longer than cardo; mala digitiform, tapering toward apex, 0.9 x as long as palpomere I, with apical sensory appendages and two pores; palpifer with one seta. Maxilla and labium as in L. hardeni , except maxillary palpomere length ratios: 1.0:1.4:2.7; ligula separated from prementum by a distinctly sclerotized transverse strip; palpomere I 1.2 x as long as II; palpomere II bent near apex. Dorsal sclerites of thorax with ecdysial lines along midline; prothorax narrow, 1.1 x as long as wide, narrowed anteriorly, chaetotaxy as in Fig. 12A ; thoracic tergite II longer than tergite III; abdominal sclerites lightly sclerotized, with two small pleural sclerites per segment on each side; basal segment of urogomphus 4 x as long as terminal segment, with seven prominent lateral setae; terminal segment of urogomphus slender, with one short and one long apical seta. Etymology. The specific name is Latin (singular, neuter), meaning hidden or concealed, in reference to the species' endogean habitat. Distribution and ecology. Lathrobium absconditum is known from Highlands County and Bath County, Virginia (Fig. 13 ). Two specimens were collected near the mouth of Owl Cave, but none were found inside the cave. All specimens were collected with buried pipe traps, which suggests they are hypogean. Adults collected Mar-Oct. Larvae collected in Oct. Males and females have yet to be collected together. Remarks. Larvae were associated with adults by DNA barcoding.