Eutheimorphus thailandicus, Jałoszyński, 2023

Jałoszyński, Paweł, 2023, The first species of Eutheimorphus Franz & Löbl in Thailand (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5323 (3), pp. 435-439 : 436-439

Eutheimorphus thailandicus sp. n.

( Figs 1–9 )

Type material. Holotype: THAILAND (Phetchaburi Province): ♁, two labels: “THAILAND: Phetchaburi / Kaeng Krachan Nat. Pk / 450 m, 19.XI.1985 / Burckhardt-Löbl” [white, printed], “ EUTHEIMORPHUS / thailandicus m. / P. Jałoszyński, 2023 / HOLOTYPUS” [red, printed] ( MHNG).

Diagnosis. Head with pair of oblique grooves extending from posteromesal margins of eyes to frontal glands; grooves on pronotum forming distinctly transverse figure; each elytron with two shallow, broad and diffuse but well discernible longitudinal impressions extending from base to posterior 1/3–1/4; aedeagus with symmetrical endophallus composed of elongate sclerites, with bell-shaped proximal structure.

Description. Body of male ( Figs 1–2 ) elongate, strongly convex, uniformly and moderately dark brown; setae slightly lighter than cuticle; BL 0.74 mm.

Head ( Figs 3–5 ) broadest at large, strongly convex and coarsely faceted eyes, HL 0.09 mm, HW 0.18 mm; vertex and frons medially confluent, flattened, frons on each side with minute frontal gland ( Fig. 3 ; fg) and oblique groove extending from frontal gland to posteromesal margin of eye; supraantennal tubercles weakly elevated. Punctures on frons and vertex ( Fig. 3 ) fine and sparse, inconspicuous; setae sparse, nearly recumbent. Ventral surface ( Figs 4–5 ) with transverse microsculpture on gular plate and sharply marked gular sutures, each mandible with three sharp teeth. Antennae ( Figs 1–2 ) moderately slender, with clearly delimited trimerous club, AnL 0.30 mm; scape weakly elongate, pedicel 1.8 × as long as broad, antennomere 3 weakly transverse, 4 and 5 each about as long as broad, 6–8 each weakly transverse, 9 much larger than 8, weakly transverse, 10 about as long as broad, 11 slightly longer than 9–10 combined, distinctly broader than 10 and about 1.8 × as long as broad. Antennomeres 1–8 sparsely covered with setae, antennomeres 9–11 each with much denser setation.

Pronotum ( Fig. 6 ) subtrapezoidal, nearly equally broad between base and anterior third; PL 0.20 mm, PW 0.25 mm; anterior margin broadly rounded, anterior corners not marked, lateral margins nearly straight; posterior corners nearly right-angled and with acute tips; posterior margin weakly bisinuate with median flattening in front of mesoscutellar shield. Pronotal base with pair of small and indistinct inner pits ( Fig. 6 ; abp) and pair of shallow and broad outer impressions near lateral corners, inner antebasal pits connected by system of distinct grooves forming approximately H-shaped pattern, anteriorly slightly exceeding middle of pronotum. Punctures and setae on pronotal disc similar to those on frons and vertex. Ventrally ( Fig. 4 ), prothorax with nearly impunctate and largely asetose hypomera (with setae distributed only along lateral margins); prosternal process ( Fig. 4 ; psp) narrow and elongate, in lateral view not elevated beyond ventral surface of procoxae.

Mesoscutellar shield ( Fig. 6 ) broadly triangular with rounded posterior margin and impressed at middle near base.

Mesoventrite ( Fig. 4 ) with broad, subtriangular and distinctly impressed procoxal rests behind anterior margin, mesoventral process ( Fig. 4 ; msvp) subtriangular with rounded posterior margin, slightly broader than prosternal process, weakly elevated ventrally.

Elytra ( Figs 1–2 ) together oval with subtruncate apices, broadest slightly in front of middle; EL 0.45 mm, EW 0.35 mm, EI 1.29; each elytron with two vestigial basal foveae ( Fig. 6 ; bef) and two broad, shallow and diffuse longitudinal impressions extending from side of mesoscutellar shield and from outer basal elytral fovea to posterior 1/3–1/4 of elytral length. Punctures and setae similar to those on pronotum.

Metaventrite ( Fig. 4 ) subquadrate, with broad, subtrapezoidal metaventral intermetacoxal process ( Fig. 4 ; mtvp) with clearly marked posterolateral corners.

Hind wings long and functional.

Legs ( Figs 1–2 ) moderately long and slender, unmodified.

Aedeagus ( Figs 7–8 ; because of extremely small size and fragile, weakly sclerotized walls prone to distortion studied only in ventral view) elongate, drop-shaped; AeL 0.13 mm; median lobe in ventral view broadest near proximal third, strongly tapering distally and with rapidly narrowed, distally broadly rounded apex; endophallus with symmetrical sclerites forming subtriangular proximal structure and distal groups of longitudinal elongate sclerites; parameres slender, each with 2 apical and 1 subapical setae.

Female. Unknown.

Distribution. Central Thailand ( Fig. 9 ).

Etymology. The adjective thailandicus refers to the country name.

Remarks. Eutheimorphus paradoxus and E. thailandicus share a similar body length, shape and pigmentation. However, E. paradoxus lacks the grooves on the head, and the pronotal grooves in E. thailandicus form a transverse, whereas those in E. paradoxus a subquadrate figure (illustrated in Franz & Löbl (1990): fig. 1). Moreover, E. thailandicus has two shallow longitudinal impressions on each elytron, which E. paradoxus lacks. The aedeagus in E. thailandicus has a symmetrical aedeagus, whereas that of E. paradoxus is clearly asymmetrical ( Fig. 9 ).

Figures

FIGURE 9. Distribution of Eutheimorphus, with aedeagi in ventral view (that of E. paradoxus reproduced from Franz & Löbl (1990)).

FIGURES 1–2. Eutheimorphus thailandicus sp. n., holotype male, dorsal habitus.

FIGURES 3–8. Eutheimorphus thailandicus sp. n., holotype male. Posterolateral region of head in dorsal view (3); Head, thorax and base of abdomen in ventral view (4); mouthparts in ventral view (5); pronotum and elytral base in dorsal view (6); aedeagus in ventral view (7–8). Abbreviations: abp, antebasal pit; bef, basal elytral foveae; fg, frontal gland; md, mandible; mn, mentum; msvp, mesoventral process; mtvp, metaventral process; mxp, maxillary palp; psp, prosternal process.