Mexiconnus triops, Jałoszyński, 2022

Jałoszyński, Paweł, 2022, The first record of Mexiconnus Jałoszyński in Costa Rica with description of a new species (Coleoptera, Staphylinidae, Scydmaeninae), Zootaxa 5213 (5), pp. 591-595 : 592-594

Mexiconnus triops sp. n.

( Figs 1–8 )

Type material studied. Holotype ( Costa Rica ): ♂, two labels: “ COSTA RICA, San Jose P. / Orosi cant., Siberia env. / 9.5561883N, 83.7155822W / sifting in montane cloud / forest, moss/litter, 7.i.2021 ” [white, printed], “ MEXICONNUS / triops m. / P. Jałoszyński, ’22 / HOLOTYPUS” [red, printed] ( MNHW).

Diagnosis. Male: microphthalmous, each eye composed of only three cornea lenses forming elongate triangle; protibiae much thicker than meso- and metatibiae; wingless, elytra lacking humeral calli and broadest distinctly in front of middle; apex of aedeagus in ventral view broadly subtriangular, distal region of each paramere in lateral view straight and with broad, blunt apex.

Description. Body of male ( Fig. 1 ) elongate, strongly convex; pigmentation light brown, legs, antennae and palps distinctly lighter, body covered with setae slightly lighter than cuticle; BL 1.13 mm.

Head broadest at eyes, nearly round, HL 0.18 mm, HW 0.21 mm; tempora in dorsal view much longer than eyes and evenly converging posterad, posterior margin of vertex weakly arcuate, not bulging posterodorsad. Eyes barely discernible, each composed of three tiny cornea lenses forming elongate obtuse-angled triangle. Frons and vertex with unremarkable, fine punctures, glossy; setae sparse and suberect, tempora lacking bristles. Antennae slender, with loosely assembled distinctly delimited trimerous club, AnL 0.48 mm, scape and pedicel each elongate, antennomeres 3–7 each about as long as wide, 8 slightly smaller than 7, about as long as broad, 9 and 10 each slightly transverse, 11 as broad as 10, shorter than 9 and 10 combined, as long as broad.

Pronotum with rounded sides, broadest between middle and anterior third, PL 0.33 mm, PW 0.29 mm. Sides strongly rounded in anterior half, posteriorly weakly sinuate, anterior corners indistinct, anterior margin weakly arcuate, posterior corners obtuse-angled, posterior pronotal margin nearly straight and distinctly shorter than anterior margin. Pronotal disc with distinct transverse antebasal groove connecting pair of small round inner pits. Punctures and setae on disc similar to those on frons and vertex, unremarkable; sides of pronotum with long and thick bristles.

Elytra together oval, broadest distinctly in front of middle; EL 0.63 mm, EW 0.40 mm, EI 1.56; humeral calli and basal impressions lacking; elytral apices separately rounded. Punctures as indistinct as those on pronotal disc; setae dense, distinctly longer and more erect than those on pronotum.

Hind wings absent.

Legs slender except for modified fore legs. Profemora distinctly thicker than meso- and metafemora, protibiae strongly thickening distad and flattened laterally, weakly recurved; protarsus ( Figs 2, 3 ) broadened but strongly narrowing distally from base, tarsomere 1 ventrally densely covered with long setae.

Aedeagus ( Figs 4–7 ) drop-shaped and elongate, AeL 0.19 mm; median lobe in ventral view broadest near base, with broadly rounded sides, apex elongate triangular, endophallic structures weakly sclerotized and relatively indistinct, composed of pair of longitudinal lateral rods connected proximally by a broadly inversely V-shaped sclerite; parameres in lateral view with broad bases and gradually narrowing distad, to blunt and straight apices.

Female. Unknown.

Distribution. Central Costa Rica ( Fig. 8 ).

Etymology. The noun triops is a new Latin word composed of the Latin tri and Greek ops, which refers to the three cornea lenses visible on each side of the head in male.

Remarks. Besides clearly different aedeagi ( Fig. 8 ), males of the two nominal species of Mexiconnus differ strikingly in the size of eyes, thickening of the protibiae and the silhouette of the elytra. The presumable sexual dimorphic features, however, are similar in M. mexicanus and M. triops . Males of both species have strongly broadened protarsi distinctly narrowing distally, and the first tarsomere ventrally densely covered with long setae (setae omitted in Figs 2, 3 ).

The light pigmentation, lack of wings and, above all, the strongly reduced eyes suggest an endogean habit of this interesting species. In contrast, males of M. mexicanus have conspicuously large and multifaceted eyes, long, functional wings, and their body pigmentation is much darker.

Figures

FIGURE 8. Distribution of Mexiconnus species, with aedeagi in ventral view (that of M.mexicanus reproduced from Jałoszyński (2013)).

FIGURES 1‒7. Mexiconnus triops sp. n., holotype male. Dorsal habitus (1); protarsus in lateral (2) and ventral (3) views (setae omitted); aedeagus in ventral (4, 6) and lateral (5, 7) views.