A review of Paraxenopygus Bernhauer (Insecta: Coleoptera: Staphylinidae), with description of two new species Author Chatzimanolis, Stylianos Department of Biology, Geology and Environmental Science, University of Tennessee at Chattanooga, Chattanooga, TN, USA; Author Brunke, Adam J. Canadian National Collection of Insects, Arachnids and Nematodes, Agriculture and Agri-Food Canada, Ottawa, ON, Canada; Author Navarrete-Heredia, José L. Centro de Estudios en Zoología, CUCBA, Universidad de Guadalajara, Zapopan, México text Journal of Natural History 2024 2024-08-30 58 37 - 40 1509 1528 http://dx.doi.org/10.1080/00222933.2024.2391450 journal article 303343 10.1080/00222933.2024.2391450 5b6cb74e-6d97-4cfc-b291-0156356aa0c1 1464-5262 13758597 53764B33-1DC2-4103-97E6-4AA07C6EB12D Paraxenopygus tremolerasi Bernauer, 1911 ( Figures 1A , 2A , 3A , 4A, 4F, 4H , 5A–C , 6) Paraxenopygus tremolerasi Bernauer, 1911, p. 415 . Type material Lectotype , here designated, male with labels: ‘ Canelones [−34.53°, −56.28°] (Progreso), 25.i.1907 ’/‘ Uruguay , Tremoleras [leg.]’/‘ ♂ ’/‘ Paraxenopygus tremolerasi Brnh Typus’/‘Chicago NHMus M. Bernhauer Collection’ /‘Bernhauer Brazil Types Photographed E. Caron 2017’/‘FMNHINS3048928’/‘ Lectotype Paraxenopygus tremolerasi Bernhauer des. Chatzimanolis, Brunke and Navarrete-Heredia’. In the collection of FMNH . Paralectotype , female with labels: ‘ Canelones [−34.53°, −56.28°] ( Progreso ), 8 .ii.[19] 08’/‘ Uruguay , leg . Tremoleras’ /‘ ♀ ’/‘ Paraxenopygus tremolerasi Brnh Cotypus’ / ‘FMNHINS45 18369’/‘ Paralectotype Paraxenopygus tremolerasi Bernhauer det. Chatzimanolis, Brunke and Navarrete-Heredia’. In the collection of FMNH . Additional materials ARGENTINA : Buenos Aires : Buenos Aires , km 26 F .C.G.B. [ Campo de Mayo , −34.53°, −58.66°], 20 .x.1990, Di Iorio leg . ( 1 male FMNH ) ; Córdoba : Alta Gracia [−31.66°, −64.43°], xii . [1]920 ( 1 female NHMUK ); same locality and date, Scheerpeltz coll . ( 2 female NMW ); same locality, xii .[1] 921, in nest of Acromyrmex heyeri , Bruch leg . Bernhauer coll . ( 1 female FMNH ); Córdoba [−31.41°, −64.20°], i .1939, M .J . Viana leg., Bernhauer coll ., SM00063587 , FMNHINS4518371 ( 1 female SEMC ; 1 female FMNH ); Embalse de Molino [ Embalse Los Molinos ,−31.82°,−64.52°], 29 . xi .1971, L . Herman leg ( 7 male , 5 female AMNH ) ; Santiago del Estero : Bords du Rio Salado , xii .1909, E. R . Wagner leg ., Cameron Coll. ( 1 female NHMUK ) ; Tucumán : Cruz Alta , La Soledad , Cañete [−27.08°, −65.08°], 14 .ii.[19]67, E . Bucher leg ., malaise ( 1 female IFML ); Concepción [−27.35°, −65.59°], A . Gassner leg ., FMNHINS4518373 ( 1 male FMNH ); Trancas-Tacanas [−26.22°, −65.28°], 3 .ix–xii.[1]968, L . Stange leg ., malaise ( 1 female IFML ) ; BRAZIL : Paraná : Guarapuava [−25.39°, −51.48°], M . Scheneidel leg . ( 2 female CNC ) ; Rio Grande do Sul : Fortaleza [ dos Valos ] [−28.80°, −53.23°], 26 .viii. [19]25, with Acromyrmex , FMNHINS 4518374, FMNHINS4518375,FMNHINS4518376, FMNHINS4518378, FMNHINS4518377 ( 3 male , 3 female FMNH ); Glória [−30.08°, −51.20°], 26 .viii .1925, host Acromyrmex sp. , FMNHINS4518389, FMNHINS4518391, FMNHINS4518392, FMNHINS4518393, FMNHINS4518394, FMNHINS451 8396, FMNHINS4518397, FMNHINS4518398, FMNHINS4518399, FMNHINS4518400, FMNHI NS4518408 , FMNHINS4518407 , FMNHINS4518402 , FMNHINS4518406 , FMNHINS4518405 , FMNHINS4518404 , FMNHINS4518395 , FMNHINS4518401 , FMNHINS4518403 , FMNHINS45 18390 ( 11 male , 10 female FMNH ); same locality, 9 .vi .1925, host Atta , FMNHINS 4518383, FMNHINS4518381, FMNHINS4518382, FMNHINS4518380 ( 4 female FMNH ); unknown locality, 20 .ix .1926, FMNHINS4518379 ( 1 male FMNH ); unknown locality, 23 .viii .1925, Buck coll . ( 1 female FMNH ); unknown locality, 9 .vi .1925, Atta host ( 1 male , 1 female FMNH ) ; Santa Catarina : Nova Teutônia [Seara] [−27.25°, −50.33°], 300–500 m , xi .[19]52, F . Plaumann leg ., Newton coll . ( 1 female FMNH ); same locality, 10 .vi .1941 ( 1 female CNC ); same locality and collector, x . [19]72, with Acromyrmex ( 1 male UCR ) ; PARAGUAY : unknown department : unknown locality, Hohenau leg ., H . Jacob leg ., Scheerpeltz coll ( 1 male NMW ) . URUGUAY : Colonia : Route 21, ca 184.5 S Piedra de los Indios [−34.39°, −57.85°], 21 .xi .2008. G.J. Wibmer leg ., AJB0002044 ( 1 female FMNH ); Montevideo : Cerro de Montevideo [−34.88°, −56.26°], 12 . x.[19]33, Fernandez leg . ( 1 female NHMUK ); Montevideo [−34.89°, −56.20°], 5 .iii. [19]34, FMNHINS4518372 ( 1 female FMNH ); same locality, x .[19]29, Bernhauer coll . ( 1 female FMNH ); same locality, xi .[19]34, Bernhauer coll . FMNHINS4518370 ( 1 female FMNH ); same locality, Jungmann leg ., [19]34 ( 1 male , 1 female FMNH ) . Unknown country : Mout . 1933 Co. Castro ( 2 male , 3 female SDEI ) . Diagnosis Paraxenopyus tremolerasi can be distinguished from all other species of Paraxenopygus by the combination of the following characteristics: antennomeres 1–5 without tomentose pubescence ( Figure 4F ); head and pronotum bright metallic black-blue ( Figure 2A ); pronotum with clearly separated rows of setose punctures ( Figure 2A ); metacoxal shield elongate and narrow ( Figure 3A ); abdominal tergites 3–4 with a faint curved line posterior to anterior transverse basal line ( Figure 4H ) and the distinct aedeagus ( Figure 5A–C ). Description Forebody ( Figure 1A ) length 6.3–7.7 mm . Colour of head and pronotum bright metallic black-blue ( Figure 2A ); mesoscutellum dark brown to black; elytra orange-brown; antennae and legs brown, except coxae dark brown to black. Abdominal segments 3–6 dark brown to black, segments 7–8 orange-brown. Head width/length ratio = - 1.43–1.44. Epicranium ( Figure 2A ) with medium to large punctures, distance between punctures as wide as 0.5–1 punctures. Antennomere 1–5 without tomentose pubescence ( Figure 4F ). Mandibles with slight bend medially, appearing slightly concave at midpoint; convex apically. Neck with dense, medium-sized punctures. Pronotum width/length ratio = 1.00–1.08; pronotum with large punctures, punctures in clearly separated rows, but not evenly distributed; superior marginal line of pronotal hypomeron joins inferior marginal line at neck. Elytra length/pronotal length ratio = 1.27– 1.33; elytra with large punctures and few wrinkled irregularities between punctures. Metacoxal shield elongate and narrow ( Figure 3A ), but length of shield variable (see Discussion); abdominal tergites 3–4 with a faint curved line posterior to anterior transverse basal line ( Figure 4H ). Sternite 7 in males with transverse porose structure ( Figure 4A ); sternite 8 with V-shaped emargination ( Figure 4A ). Aedeagus as in Figure 5A–C ; in ventral view paramere parallel-sided, converging to rounded apex; paramere slightly longer and narrower than median lobe (except apically); in lateral view paramere becoming narrower with rounded apex; paramere with peg setae in multiple short rows as in Figure 5B . Median lobe in ventral view wide, converging to narrow tip; in lateral view median lobe becoming narrower, with thin apex; median lobe with small apical tooth. Endophallus in ventral and lateral view wide and rounded. Distribution Known from the provinces of Buenos Aires, Córdoba, Santiago del Estero and Tucumán in Argentina , the states of Paraná, Rio Grande do Sul and Santa Catarina in Brazil , from Paraguay , and the departments of Canelones , Colonia and Montevideo in Uruguay ( Figure 6 ). Habitat Collected in lowland tropical forests with both Acromyrmex heyeri Forel and Atta sp. ants according to the labels above. There are multiple collecting events indicating an association with Acromyrmex and only one with Atta and it is not clear whether the species is host specific.