Distribution of Rugilus mixtus (Lohse, 1956) (Coleoptera: Staphylinidae: Paederinae) in Poland with comments of its morphology and ecological preferences Author Sapieja, Mateusz 0000-0003-1151-4245 Institute of Zoology and Biomedical Research, Jagiellonian University, Gronostajowa 9, 30 - 387 Kraków, Poland. sapiejamateusz @ gmail. com, https: // orcid. org / 0000 - 0003 - 1151 - 4245 Author Ranocha, Magdalena Department of Mountain Forests, Forest Research Institute, Fredry 39, 30 - 605 Kraków, Poland. Author Melke, Andrzej 0000-0002-2039-7979 Department of Zoology, Institute of Biology and Environmental Protection, Pomeranian University, 76 - 200 Słupsk. kusakowaty @ gmail. com, https: // orcid. org / 0000 - 0002 - 2039 - 7979 text Zootaxa 2022 2022-02-18 5100 2 249 258 journal article 20588 10.11646/zootaxa.5100.2.4 21987729-d480-4305-8de5-9d38e4399e2d 1175-5326 6145690 A21EE081-4AE7-4129-814D-49605C8DC24D The identification key for central European representatives of the genus Rugilus with yellow-tipped elytra: 1. Body length not smaller than 5.0 mm................................................................ R. similis – Body length smaller than 5.0 mm..........................................................................2 2. Head oval, wider than elytra (HI—1:1.13~1.21, HEI—1: 1.06–1.10). Eye twice as long as temple (ETI—1.96–2.14). Elytra black, sometimes with a dark maroon tinge. Legs yellow. Male abdominal sternite VIII with two pairs of long symmetrically set bristles in the middle of a segment and posterior margin ( Fig. 9 ). Aedeagus as in Fig. 17, 20............... R . erichsonii – Head width equal to or less than elytra width, eye shorter than two temple lengths. Aedeagus different................... 3 3. Head oval, wider than long (HI ranges 1.13–1.14), as wide as or slightly narrower than elytra (HEI—1:0.97). Fourth segment of antennae clavate (4ASI—1:0.83–0.93) ( Fig. 13 ). Eye almost twice as long as temple (ETI—1.83–1.87). Elytra dark maroon. Legs maroon. Length index of the first posterior tarsal segment to its total length 1:0.28–0.29 ( Fig. 11 ). Male abdominal sternite VIII triangularly cut ( Lohse 1956 ). Aedeagus as in Figs. 15, 18............................................ R . mixtus – Head slightly wider than length (HI ranges 1:1.06–1.09) and much narrower than elytra (HEI—1:0.86–0.90). Fourth antennal segment barrel-shaped (4ASI—1:0.72–0.81) ( Fig. 14 ). Eye about 1.5 times longer than temple (ETI ranges 1:1.50–1.55). Elytra black with markedly contrasting yellow spots at posterior margins. Legs yellow. Length index of the first posterior tarsal segment to the total length 1:0.31–0.33 ( Fig. 12 ). Male abdominal sternite VIII rounded cut, with one pair symmetrically set long bristles at posterior margin ( Fig. 10 ). Aedeagus as in Figs. 16, 19.................................. R . orbiculatus