Bythinus tridentus Bekchiev & Kostova, 2025

Bekchiev, Rostislav, Kostova, Rumyana, Langourov, Mario & Simov, Nikolay, 2025, The subfamily Pselaphinae (Coleoptera: Staphylinidae) of North Bulgaria. I, Zootaxa 5647 (3), pp. 289-300 : 296-298

Bythinus tridentus Bekchiev & Kostova , sp. nov.

( Figs. 2f , 3 )

Material examined: (8 ♂♂, 18 ♀♀). Holotype: 1 ♂: Devetashka Cave entrance, N43.2339 E24.8851, 28.1.2022, sifting leaf litter, leg. R. Bekchiev, N. Simov, M. Langoutov ( NMNHS) . Paratypes: (7 ♂♂, 18 ♀♀): 4 ♀♀: Devetashka Cave entrance, N43.2339 E24.8851, 28.1.2022, leg. R. Bekchiev; N. Simov, M. Langoutov ( NMNHS) ; 3 ♂♂, 3 ♀♀: Mitrovtsi , N43.4123 E22.9403, 2.5.2015, leg. R. Bekchiev ( NMNHS) ; 4 ♂♂, 11 ♀♀: Kula Village , N43.9204 E22.5321, 6.8.2016, leg. R. Bekchiev ( NMNHS) .

Description. Body dark reddish-brown, BL 1.45–1.50 mm. Legs, antennae and maxillary palpi yellowishbrown. Pubescence on head, pronotum and elytra gold, long and sub-erected. Head ( Fig. 3a ) wider than long, HL 0.22–0.24 mm, HW 0.27–0.30 mm. Vertex smooth with narrow transverse carina in posterior part, reaching level of vertexal foveae. Frons with deep depression between antennal tubercles; triangular anteriad. Eyes large, with 20–25 ommatidia each. Gular region with convex oval median protuberance. Antennae long (0.46 mm), scape simple, pedicel securiform ( Fig. 3b ). Antennomeres 3–8 subequal in length, 9 wide than long, 10 as wide as long, 11 large and fusiform. Maxillary palpi long, palpomere 1 small, 2 long, pedunculate, 3 small, 4 large, its dorsal part with large, ovoid medium protuberance ( Fig. 3c ). Pronotum wider than long, PW 0.34–0.36 mm, PL 0.28–0.30, widest in anterior half. Elytra wider than long, EW 0.54–0.56 mm, EL 0.48– 0.40 mm. Abdomen AW 0.50–0.52 mm, AL 0.38–0.40 mm. Legs slender, all tibiae simple. Aedeagus 0.34–0.36 mm long, parameres with large, preapical tooth, internal sac with two symmetrical sclerites, each bearing one large and one small, pointed tooth ( Fig. 3d ).

Sexual dimorphism. Female similar in length and habitus to male, only the last palpomere and the gular region is flat and simple.

Differential diagnosis. Bythinus tridentus sp. nov. belongs to the Bythinus securiger Reichenbach, 1816 species group and within the group can be easily recognized by the combination of the following characters: 1) shape of the antennae, 2) shape of the last palpomere, and 3) shape of the aedeagus. It is closely related to Bythinus balkanicus Reitter, 1885 from which it differs by the larger size of body, the presence of the large protuberance on the last palpomere and by the different shape of the aedeagus.

Biology. All specimens were collected by sifting of leaf litter from the bank of a small rivers or found in MSS traps in the karst area ( Fig. 2f ).

Etymology. named after the trident shape of the internal apophysis of the aedeagus.

Figures

FIGURE 2. Localities in North Bulgaria. a) Rusenski Lom; b) bank of Rositsa River; c) Marshes near Orsoya Village; d) Natural and seminatural steppes near Sovata Village; e) Entrance of Parnitsite Cave (Bezhanovo Village); f) Devetashka Cave (Devetaki Village).

FIGURE 3. Bythinus tridentus sp. nov. a) head, male (scale 0.1 mm); b) scape and pedicel, dorsal view (scale 0.05 mm); c) maxillary palp, dorsal view (scale 0.1 mm); d) aedeagus, ventral view (scale 0.1 mm).