Costa Rica, San José, Cerro de la Muerte.

Holotype, male: • Costa Rica, Cerro de la Muerte, Calle de Torres, 3,300 m, 27.ii.2024, 9.57041°N, 83.75411°W, Springer & Balke (CR_MB_2024_03) (MZUCR).

Paratypes (N = 157). 115 exx. Same label data as holotype (MZUCR, ZSM); • 1 ex. Costa Rica, Cerro de la Muerte, Calle de Torres, 3,350 m, 27.ii.2024, 9.56658°N, 83.75469°W, Springer & Balke (CR_MB_2024_04) (MZUCR, ZSM); • 4 males, 2 females, 32 exx., Costa Rica, Cerro de la Muerte, Calle de Torres, 3,300 m, 17.vii.2024, 9.57041°N, 83.75411°W, Bilton (CBP, ZSM); • 1 male, 1 female, Costa Rica, San José, Chirripó summit region, 18.iii.1971, Hohmann (loc. 2) (NMB) (voucher MB9030).

We saw one additional specimen from the Páramo de Chirripó in the Costa Rican National Museum insect collection which we could, however, not borrow.

Habitus with slight but obvious discontinuity between pronotum and elytra (Fig. 1A, B), pronotum widest before base and more parallel sided laterally. Total length (TL) of beetle: 2.0 mm; length without head (TL-h): 1.8 mm; maximum width (TW): 1 mm.

Colour. Dark brown to blackish dorsally and ventrally, basal antennomeres, base of meso- and metatibia contrastingly of lighter colour (as in Fig. 1B).

Surface sculpture. Head with few larger and smaller setiferous punctures; with distinct microreticulation except on middle of head between the eyes (as in Fig. 1B). Pronotum and elytra shiny; with moderately dense and coarse setiferous punctation (as in Fig. 1B).

Structures. Antenna filiform. Head without occipital line; with rounded clypeus. Pronotum with distinct lateral bead; with distinct long and deep basal striae (Fig. 1A). Elytra with distinct basal striae; without sutural line; without basal epipleural transverse carina. Metathoracic wings not examined in holotype (in paratype: short, about half the length of elytra, Fig. 1B).

Genitalia. Median lobe of aedeagus slender with simple curvature in basal 1/3, then broadening and forming a convexity on dorsal margin (in lateral view), then significantly narrowing towards tip (Fig. 1C); gradually narrowing towards a narrow tip in ventral view (Fig. 1D); parameres of simple “Bidessini” type, two-segmented (Fig. 1E).

Female. Pronotum and elytra can show a varying extent of microreticulation. This ranges from having a few meshes to being very obviously microreticulate on the disc of the pronotum and the elytra being only faintly microreticulate apically, to showing visible microreticulation on entire apical 1/3 to ½. Very few specimens, including the single female from Páramo de Chirripó, have a completely dull dorsal surface.

Variation. Size variation of the paratypes is TL 2.0–2.2 mm; TL-h 1.7–1.9 mm; TW 1.0–1.1 mm (specimen from Páramo de Chirripó slightly larger, TL 2.3 mm; TL-h 2.0 mm; TW 1.1 mm). Dorsal colour can be lighter brown to mostly dark orange-brown (see Fig. 1A). Usually without occipital line, few specimens with faint line, more like a few serial punctures connected by a very shallow impression.

Named after the type locality, the mountain Cerro de la Muerte.

Distinguished from the other species of Liodessus by the diagnostic combination of the following features: species from high altitude of Costa Rica; with slight but obvious discontinuity between pronotum and elytra; head without (or with really faint) occipital line; pronotal and elytral striae present; wings reduced considerably; shape of median lobe.

Known from high altitudes of Costa Rica > 3,000 m (Fig. 3).

Collected from small, shallow to very shallow puddles beside a gravel road, likely with running seepage water for much of the year (Fig. 4A, B) as well as water at a small well nearby (Fig. 4C).

Costa Rica, Cartago, Paraíso Quetzal.

Holotype, male: • Costa Rica, Páramo, Paraíso Quetzal, 2,760 m, 10.-11.iii.2022, 9.6478°N, 83.8452°W, Springer & Balke (CR_MB_2022_01) (MZUCR).

Paratypes (N = 224). 130 exx., same data as holotype (MZUCR, ZSM); • 49 exx, Costa Rica, Páramo, Paraíso Quetzal, 2,760 m, 27.ii.2024, 9.64788°N, 83.84528°W, Springer & Balke (CR_MB_2024_05) (MZUCR, ZSM); • 3 males, 3 females, 13 exx, Costa Rica, Páramo, Paraíso Quetzal, 2,760 m, Bilton (CBP, ZSM); • 6 exx., Costa Rica: Cartago, Coris, roadside ditch, 1,380 m, 28.ii.2024, 9.86012°N, 83.96800°W, Springer & Balke (CR_MB_2024_06) (MZUCR, ZSM) (incl. vouchers MB10101–MB10108, MB10278, MB10279); • 6 exx., Costa Rica: Cartago, Rio Coris, creek, 1,390 m, 28.ii.2024, 9.86271°N, 83.98820°W, Springer & Balke (CR_MB_2024_07) (MZUCR, ZSM); • 14 exx., Costa Rica: Cartago, Alto de Ochomogo, 1,500 m, 20.xi.1955, Malkin (CAS, ZSM) (incl. vouchers MB9303, MB9304).

Habitus only with slight discontinuity between pronotum and elytra (as in Fig. 2A, D), pronotum widest before base and more rounded laterally. TL: 2.2 mm; TL-h: 1.9 mm; TW: 1.0 mm.

Colour. Very dark brown to blackish dorsally and ventrally, pronotum of lighter colour towards lateral sides, lateral margin yellowish; elytra with lighter colour pattern in the form of longitudinal patches as in Fig. 2D. Basal antennomeres and legs contrastingly of lighter colour (Fig. 2D).

Surface sculpture. Head with few larger and smaller setiferous punctures (as in Fig. 2A, D); with distinct microreticulation except on middle of head between the eyes. Pronotum and elytra shiny; with moderately dense and coarse setiferous punctation.

Structures. Antenna filiform. Head with occipital line; with rounded clypeus. Pronotum with distinct lateral bead; with distinct long and deep basal striae (as in Fig. 2A, D). Elytra with distinct basal striae; without sutural line; without basal epipleural transverse carina. Metathoracic wings not examined in holotype (in paratype: fully developed).

Genitalia. Median lobe of aedeagus simply curved and relatively broad, narrowing towards apex; tip broadly rounded in ventral view, of characteristic spoon- or duck beaked shape; parameres of simple “Bidessini” type, two segmented (Fig. 2C).

Female. Elytra with visible microreticulation on apical 1/3 to ½.

Variation. Size variation of the paratypes is TL 2.2–2.3 mm; TL-h 1.9–2.0 mm; TW 1.1–1.2 mm. The elytra may show contrasting pattern of yellowish bands in freshly hatched or generally very pale specimens. The beetles from Alto de Ochomogo (CAS) appear dark orange, although a darker colour pattern is still obvious. This appearance might be an artefact of longer storage and/or method of preservation. Our freshly collected specimens from the nearby Coris area are darker.

Named after the type locality, which is 650 m north-east from the Paraíso Quetzal Lodge.

This species can be distinguished from other species of Liodessus by the following combination of diagnostic characters: Occurrence in Costa Rica; shape of median lobe (tip in ventral view of characteristic spoon- or duck beaked shape).

Known from the central valley near San José and higher altitudes of Costa Rica nearby, up to around 2,800 m (Fig. 3).

Collected from small, shallow to very shallow puddles as well as edge of lagoon (Fig. 4D) in Páramo, as well as densely vegetated roadside ditch (Fig. 4E) and densely vegetated margin of creek (Rio Coris) (Fig. 4F).