Euconnus (Rhomboconnus) rhombopanamensis Jałoszyński 2017, sp. n.

Euconnus (Rhomboconnus) rhombopanamensis sp. n.

(Figs 4, 12, 23–24, 31–32, 52)

Holotype: Panama (Panamá Province): ♂, two labels: "PANAMA, near Lago Bayano / 08/08/2014 / 9,17°N, 78,74°W / forest litter, leg. Tim Struyve" [white, printed], " EUCONNUS / (RHOMBOCONNUS) / rhombopanamensis m. / P. Jałoszyński, '17 / HOLOTYPUS" [red, printed] (MNHW). Paratypes (3 ♂♂): 1 ♂, same data as for holotype; 1 ♂, "PANAMA, Mogue / 10/08/2014 / 8,247°N, 78,156°W / litter layer, leg. Tim Struyve" [white, printed]; 1 ♂, "PANAMA, Cerro Azul / 14/05/2014 / 9,199°N, 79,395°W / litter layer, leg. Tim Struyve" [white, printed] (paratypes in TSCB and cPJ).

Diagnosis. BL ~ 2 mm; head and pronotum asetose (except for bristles), elytra with very sparse and short but distinct setae; tempora strongly narrowing posteriorly with very short, barely discernible posterior portion bent mesally; pronotum broadest in posterior third and strongly narrowed posteriorly and anteriorly; pronotal base with transverse groove; parameres distinctly broadened in subapical region; median endophallic sclerite (i.e., the shortest one) with distinctly curved distal portion.

Description. Body of male (Fig. 4) strongly convex, elongate, with moderately long appendages, BL 1.76 mm; cuticle glossy, uniformly dark brown, vestiture slightly lighter than cuticle.

Head (Fig. 12) strongly narrowing posteriorly, broadest at eyes, HL 0.45 mm, HW 0.38 mm; vertex and frons confluent, evenly and relatively strongly convex except frons in front of eyes which steeply declines anteriorly, posterior margin of vertex projecting posteriorly as subrectangular lobe about as broad as 1/3 of HW; tempora indistinctly convex with extremely short, barely noticeable posterior portion bent posteromesally; supraantennal tubercles barely marked; eyes large, finely faceted and weakly projecting from silhouette of head. Punctures on vertex and frons very fine and inconspicuous; setae absent, posterior portion of each temple with small tuft of thick and relatively short bristles. Antennae slender, AnL 1.23 mm; all antennomeres except III elongate, III slightly transverse; antennomeres VII–XI forming indistinctly delimited club, antennomere XI only slightly longer than X, ~1.5 times as long as broad, indistinctly flattened.

Pronotum (Fig. 12) in dorsal view broadest near posterior third and strongly narrowing anteriorly and posteriorly, PL 0.43 mm, PW 0.50 mm; base with long, narrow and deep transverse groove. Punctures as fine as those on frons and vertex, pronotal disc asetose except for lateral bristles.

Elytra suboval, broadest near middle, EL 1.08 mm, EW 0.88 mm, EI 1.23; apices separately rounded. Punctures on elytral disc inconspicuous; setae short but distinct, sparse and suberect.

Legs moderately long and slender; protrochanter with distinctly projecting distoventral corner forming small pointed tooth.

Aedeagus (Figs 23–24, 31–32) stout, AeL 0.38 mm, in ventral view drop-shaped with lateral margins abruptly bent mesally in subapical region; endophallus with four long sclerites (Fig. 52), of which the longest one has its apical portion rapidly narrowed and developed as thin finger-like and straight process; parameres distinctly broadened in subapical region.

Female. Externally differs from male in unmodified protrochanter; BL 1.95–2.03 mm; HL 0.43–0.48 mm, HW 0.35–0.36 mm, AnL 1.20–1.25 mm; PL 0.43–0.45 mm, PW 0.5 0–0.53 mm; EL 1.10–1.13 mm, EW 0.86–0.88 mm, EI 1.26–1.29.

Distribution. Central-eastern Panama, Panamá Province, and eastern Panama, Darién Province, Chepigana District.

Etymology. Combination of the subgeneric name Rhomboconnus and the country name Panama.

Remarks. Euconnus rhombopanamensis is a small (~ 2 mm BL) and inconspicuous Rhomboconnus with asetose dorsum of head and pronotum and very sparsely setose elytra. It can be confused with species with similarly asetose heads, as E. rhomboimitator and E. trianguliceps. It differs from the former mainly in endophallic structures, i.e., the shape of sclerites of the inner sac, especially the median (the shortest) sclerite, which in E. rhomboimitator is straight and long, whereas that in E. rhombopanamensis is curved and much shorter. Moreover, E. rhomboimitator has distinctly denser and longer setae on the elytra. Euconnus trianguliceps, in turn, has the pronotum very weakly narrowed behind its broadest place and with a pair of indistinct antebasal pits, lacking the transverse groove, which in E. rhombopanamensis is present and very distinct.