Balligratus humerangulus, Moret, Pierre & Ortuño, Vicente M., 2017

Moret, Pierre & Ortuño, Vicente M., 2017, Balligratus, new genus of wingless ground beetles from equatorial Andean montane forest (Coleoptera: Carabidae: Lachnophorini), Zootaxa 4258 (2), pp. 101-120 : 104-108

Balligratus humerangulus sp. nov.

Holotype, ♂, ECUADOR: Provincia Cotopaxi, Otonga , 1,800 m, 3–5.VII.2001, leg. P. Moret ( MNHN).

Paratypes, ECUADOR: 3 ♂, 4 ♀, same data as the holotype ( MNHN, CPM, CVO) ; 1 ♂, 1 ♀, Provincia Cotopaxi, Otonga , 1,900 m, 07.VIII.1998, leg. I. Tapia ( QCAZ) ; 1 ♂, 1 ♀, Cotopaxi, Otonga , 1,950 m, 3– 5.VII.2001, leg. P. Moret ( CPM) ; 1 ♀, Cotopaxi, Otonga , 2,065 m, 0°25’01.2”S / 79°00’14.0”W, 21.VII.2006, leg. P.M. Giachino ( NMNH) ; 1 ♀, Cotopaxi, S. Francisco de las Pampas, Otonga , 1,950 m, 30.VII.2004, leg. G. Coaduro ( CPMG) ; 1 ♂, 1 ♀, Cotopaxi, Cantón Sigchos, Las Pampas, Bosque integral de Otonga, 11– 12.VII.2007, leg. V. Rossi (CVR) ; 1 ♂, 1 ♀, Pichincha, W. Chiriboga, old road Quito-Santo Domingo , 2,164– 2,286 m, 10.VI.1982, leaf litter, leg. H.E. Frania ( UASM) ; 1 ♂, Pichincha, S. José de Guaramal, 1,950 m, 3.VIII.2004, leg. G. Osella ( CPMG) ; 1 ♀, Pichincha, Chiriboga fra S. José e S. Juan, 2,0 0 0–2,500 m, 3.VIII.2004, leg. C. Bellò, G. Osella & M. Pogliano ( CPM) ; 1 ♂, Provincia Pichincha, km 34.5 Quito- Nanegalito , 2,500 m, 05.VIII.2004, leg. G. Osella ( CPMG) ; 1 ♂, Provincia Pichincha, Nanegalito , 2,200–2,800 m, 05.VIII.2004, leg. C. Bellò, G. Osella & M. Pogliano ( CPM) ; 2 ♂, 4 ♀, Provincia Pichincha, Nanegalito , 0°00.207’S / 78°35.450’W, 2,220 m, 27.VII.2006, leg. Bellò, Osella & M. Pogliano ( CCB and CPM) ; 1 ♂, 1 ♀, Pichincha, Lloa, Río Blanco , 2,540 m, 27.VII.2008, leg. C. Baviera, C. Bellò, G. Osella & M. Pogliano ( CPM) ; 1 ♂, 1 ♀, Prov. Pichincha, Tandayapa, Bellavista Lodge , 0°00’56.6”S / 78°40’49.1”W, 2250 m, leaf litter at night, 01.XI.2015, leg. P. Moret ( CPM) .

Description. Overall body length: 5.4 to 6.2 mm. Slender species with elongate appendages and prominent humeri ( Fig. 1 b and 2). Body tegument nigropiceous, shiny, with metallic reflections on the elytra; appendages and labrum testaceous; clypeus flavocastaneous.

Dimensions of the head: HL 1.0 to 1.05 mm; HW 1.05 to 1.1 mm. Disc with a weakly impressed polygonal, isodiametric microsculpture. Antennae almost reaching the middle of the elytra when laid along side margin. Labium: Fig. 3 a.

Pronotum convex, suborbicular (PL 1.1 to 1.25 mm; PW 1.35 to 1.5 mm), hardly transverse (PL/PW = 0.82), wider than head. Sides markedly arcuate in distal half, weakly arcuate in basal half; hind angles obtuserounded; anterior angles feebly protruding; lateral groove deep and narrow; basal margin slightly sinuate medially; basolateral depressions shallow, ill defined. Microsculpture almost obsolete on the pronotal disc, consisting of very fine transverse meshes. Lateral seta inserted at base of the distal fourth of the lateral margin. Prosternal apophysis suborbicular at apex, distinctly bordered along basal margins ( Fig. 3 b).

Elytra suboval (EL 2.9 to 3.25 mm; EW 2.0 to 2.25 mm; EW/EL = 0.69), markedly broader than pronotum (PW/EW = 0.67), with large, acute humeri protruding anterad the basal margin, which is deeply sinuate. Maximum width at middle. Disc flat; transverse microsculpture of very fine and narrow scupticells, producing an iridescent lustre. All striae deep and broad, especially the basal third of striae 5 to 7; intervals convex; scutellar striole well impressed. Anterior discal seta adjoining the 3rd stria at the height of the 4th or 5th seta of the umbilicate series; postmedian seta adjoining the 2nd stria at the height of the 7th or 8th seta of the umbilicate series. The 13 umbilicate setae in the ninth interval are distributed 5 / 1 / 7.

Legs markedly slender; meso- and metatarsi elongate in relation to the overall body length (MstL 0.9 to 1.1 mm; MttL 1.3 to 1.5 mm; [MstL+MttL]/BL = 0.41). Basal three tarsomeres slightly bisulcate dorsally, sulci deeper on the first tarsomere.

Apical margin of the last visible abdominal ventrite slightly emarginate in both sexes ( Fig. 3 c–d).

Male genitalia ( Figs. 3 e–i): median lobe relatively large (MLL 1.34 mm; MLL/BL= 0.23), ventral margin rectilinear in its entire length in lateral view; apex obtuse, slightly bent downwards, spatulate-rounded in dorsal view; basal bulb almost indistinct. Left paramere large, ellipsoidal, with sinuate margins; right paramere small, bifid apically, with a hook-like basal process. Ring sclerite elongate, narrowly ovate.

Female genitalia ( Fig. 4 ): laterotergite IX with 25–27 setae near apical margin; spermathecal duct short; spermathecal basal bulb fusiform, progressively narrowed in apical third, twice as long as apical bulb (SbbL 0.34 mm; SbbW 0.05 mm; SbbW/SbbL= 0.14); spermathecal apical bulb ampullaceous, annulate (SabL 0.17 mm; SabW 0.10 mm; SabW/SabL = 0.58).

Etymology. Combination of Latin humerus, meaning “shoulder”, and angulus, meaning “angle”, by allusion to the protruding humeri of this species.

Distribution. Pacific slope of the Western Cordillera in Northern Ecuador, from 0°03’ N to 0°25’ S, and from 1,800 to 2,500 m ( Fig. 11 ).

Way of life. Adults of this species have been found at night on leaf litter in montane forests. By day they hide in the leaf litter or under logs, rarely under stones at the edge of small forest streams.

Figures

FIGURE 1. Habitus of four Eucaerine genera. a: Amphithasus truncatus Bates, female from Brazil (MNHN); b: Balligratus humerangulus sp. nov., female paratype from Chiriboga, Ecuador (CPM); c: Aporesthus sp., female from Ecuador (UASM); d: Guatemalteca virgen Erwin, female from Costa Rica (UASM). Scale bar: 1 mm.

FIGURE 3. Balligratus humerangulus sp. nov., details of ventral side and male genitalia. a: labium; b: prosternal apophysis; c: last visible abdominal ventrite (male); d: last visible abdominal ventrite (male); e: ring sclerite; f: median lobe, left lateral view; g: left paramere; h: right paramere; i: median lobe, dorsal view. Scale bars: 0.5 mm.

FIGURE 4. Balligratus humerangulus sp. nov., female genitalia, ventral view. a: left gonocoxites and laterotergite IX; b: internal reproductive tract. Legend: bc, bursa copulatrix; gc 1, gonocoxite 1; gc 2, gonocoxite 2; lt, laterotergite IX; sg, spermathecal gland; sgd, spermathecal gland duct; sbb, spermathecal basal bulb; sab, spermathecal apical bulb. Scale bars: 0.3 mm.

FIGURE 11. Distribution of Balligratus gen. nov. in Ecuador. The ochre to brown area roughly corresponds to the montane pluvial forest. White squares: described species; black squares: undescribed species. Map base © OpenStreetMap contributors.