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 (Lathrobium) armatum Say, 1830 Lathrobium armatum Say, 1830: 40. Lathrobium deceptivum Casey, 1905: 83. New synonym. Lathrobium nigrolucens Casey, 1905: 83. New synonym. Lathrobium procerum Casey, 1905: Bernhauer and Schubert 1912 : 255. Lathrobium subaequale Casey, 1905: 82. New synonym. Type material. Holotype not examined. It was presumably lost with much of Say's collection (Mawdsley, 1993). Lectotype Lathrobium deceptivum Casey, herein designated (USNM): "N.Y. / CASEY bequest 1925 / [red] TYPE USNM 38108 / [handwritten] Lathrobium deceptivum / Lectotype Lathrobium deceptivum Casey Desg. Haberski & Caterino." Lectotype Lathrobium subaequale Casey, herein designated (USNM): "N.J. / CASEY bequest 1925 / [red] TYPE USNM 38110 / [handwritten] Lathrobium subaequale / Lectotype Lathrobium subaequale Casey Desg. Haberski & Caterino." Lectotype Lathrobium procerum Casey, herein designated (USNM): "Ill. / CASEY bequest 1925 / [red] TYPE USNM 38110 / [handwritten] Lathrobium procerum / Lectotype Lathrobioma procerum Casey Desg. Haberski & Caterino." Lectotype Lathrobium nigrolucens Casey, herein designated (USNM): "Mass/ CASEY bequest 1925 / [red] TYPE USNM 38109 / [handwritten] Lathrobium nigrolucens / Lectotype Lathrobioma nigrolucens Casey Desg. Haberski & Caterino." Other material. Canada : Ontario (1, USNM). Quebec : MRC des Deux-Montagnes , Parc National d'Oka , 06 May 2023 , R. Vigneault , handpicked near a beach (1, NBC) . USA : Illinois (6, USNM). Indiana : Allen Co. : New Haven , 15 Jun 1986 , N. M. Downie (1, UNHC) . Massachusetts : ' Mass. ' (1, MCZ) . Michigan : ' Mi. ' (2, MCZ) . Missouri : ' Mo. ' (1, MCZ) . New Hampshire : Strafford Co. : Spruce Hole Conservation Area , 3 mi SW Durham , 09 Jun 1982 , D. S. Chandler , bog margin in oak, beech, huckleberry litter (17, UNCH); same data, except 16 Apr 1982 , marsh (1, UNHC); same data, except 22 Apr 1982 , near bog edge (2, UNHC); same data, except 30 Aug 1982 , along pond (5, UNHC); Hillsborough Co. : Antrim , 11 Jun 1932 , C. A. Frost (1, UNHC); Rockingham Co. : Hampton , 15 Mar 2003 , S. A. Shaw (1, UNHC); Rockingham Co. : Hampton , 10 Jun 2011 (1, UNHC); Grafton Co. : Rumney , 22 Apr 1926 , P. J. Darlington (1, MCZ) . New York (7, USNM); North Carolina (1, MCZ). Vermont : Burlington Co. , Apr 1953 , D. S. Chandler (1, UNHC) . Diagnosis. Lathrobium armatum is similar in external appearance to L. amplipenne and L. pedale and are especially difficult to distinguish form L. praelongum . The female terminalia of L. armatum are shorter with a more convex inner margin, and its paraprocts are longer relative to the basal portion of tergite IX than in the aforementioned species. Males are easily identified by their aedeagus, which has a unique rear-facing hook projecting form the apex of the dorsal plate. Description. Large species, body length 10 mm; body coloration dark, appendages red, elytra sometimes bicolored. Gular sutures converging, nearly touching posteriorly; antennomeres V-VII as wide as long. Elytra 1.3 x longer than pronotum. Females with paraprocts undivided, apical lobes shorter than basal portion, ~ 0.9 x as long; sternite VIII conical. Male sternite VIII either with a small round emargination or no emargination. Dorsal plate of aedeagus with large, rear-facing hook (Fig. 35 ). Distribution. Canada: ON, NB, QC ( Bousquet et al. 2013 ). USA: DC, IL, IN, MA, MI , MO , NH, NJ, NY, NC , SC, VT. Remarks. We reduce Lathrobium deceptivum , Lathrobium nigrolucens , and Lathrobium subaequale to synonymy with Lathrobium armatum based on a lack of distinguishing morphological characters. Casey recognized that the herein synonymized species were difficult to discriminate and that they might not be full species. He differentiated them based on a combination of elytra length and color. Lathrobium subequale was described as having bicolored elytra, in contrast to the solid black elytra of L. armatum . However, this character is variable and specimens of L. armatum in LeConte's collection have lightly bicolored elytra. Lathrobium deceptivum and L. nigrolucens were distinguished from L. armatum based on the length of elytra relative to pronotum, but many species are dimorphic for this character. Lathrobium deceptivum was described from two males, L. subaequale from a single female, and L. nigrolucens from a short series of both. Genitalia of all of the above species were indistinguishable.