Balligratus globosus, 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 : 114-117

Balligratus globosus sp. nov.

Holotype, ♀, ECUADOR: Provincia Chimborazo, Atillo, Laguna Negra , 3,600 m, 6.I.1995, leg. P. Moret ( MNHN). Only known specimen.

Description. Overall body length: 4.44 mm. Very short species with rounded pronotum angles and suborbicular elytra ( Fig. 9 ). Body tegument brunneopiceous, shiny; appendages and labrum testaceous; clypeus flavotestaceous.

Dimensions of the head: HL 0.68 mm; HW 1.03 mm. Disc with a weakly impressed polygonal microsculpture. A shallow circular depression in place of the supraorbital sulcus. Antennae reaching the basal third of the elytra when laid along side margin. Labium: Fig. 10 a.

Pronotum convex, subtrapezoidal in form; slightly transverse, markedly broad by comparison with the width of elytra (PL 0.95 mm; PW 1.33 mm; PL/PW = 0.71; PW/EW = 0.68), wider than head. Sides of the pronotum arcuate; anterior angles feebly protruding; hind angles rounded; lateral groove deep and narrow; basal margin weakly sinuate medially; basolateral depressions shallow, ill defined. Microsculpture of the disc transverse and shallow. Lateral seta inserted at base of the distal third of the lateral margin. Prosternal apophysis suborbicular at apex, distinctly bordered along basal margins, sulci convergent toward discal area ( Fig. 10 b).

Elytra short (EL 2.28 mm; EW 1.93 mm; EW/EL = 0.84), suborbicular in shape, with effaced humeri; maximum width at middle. Basal margin slightly sinuate; apex more rounded than in the preceding species. Microsculpture of the disc transverse and shallow. All striae well impressed; intervals flat. Scutellar striole short, obsolete. The position of the discal setae is asymmetrical in the holotype and only known specimen: left elytron as in other Balligratus species, the first seta adjoining the 3rd stria at the height of the humeral umbilicate series, the second seta adjoining the 2nd stria at the height of the 7th or 8th seta of the umbilicate series; right elytron anomalous, the first seta adjoining the 2nd stria, the second seta anterad the middle, adjoining the 3rd stria. The 13 umbilicate setae in the ninth interval are distributed 5 / 2 / 6.

Legs short and robust; meso- and metatarsi stocky in relation to the overall body length (MstL 0.62 mm; MttL 0.81 mm; [MstL+MttL]/BL = 0.32). First tarsomere slightly bisulcate dorsally.

Apical margin of the last visible ventrite slightly emarginate in the female ( Fig. 10 c).

Female genitalia ( Fig. 10 d–f): laterotergite IX with 17–19 setae near apical margin; spermathecal duct long; spermathecal basal bulb very slender, strongly narrowed at apex, not longer than apical bulb (SbbL 0.30 mm; SbbW 0.03 mm; SbbW/SbbL = 0.10); spermathecal apical bulb ampullaceous, not distinctly annulate (SabL 0.30 mm; SabW 0.07 mm; SabW/SabL = 0.23).

Male unknown.

Comment. The spermathecal gland was lost during the dissection process; this is the reason why it is not depicted in the figure that illustrates the genitalia of this species ( Fig. 10 f).

Etymology. Latin adjective meaning “globular”.

Distribution. Pacific slope of the Western Cordillera in Central Ecuador, in the uppermost fringe of the montane forest ( Fig. 11 ). Type locality at 2°10’43” S / 78°30’06” W.

Way of life. Active on leaf litter by night, between 8 and 10 PM. Collected by means of pitfall trap.

Figures

FIGURE 9. Balligratus globosus sp. nov., female holotype, habitus in dorsal view. Scale bar: 1 mm.

FIGURE 10. Balligratus globosus sp. nov., details of ventral side and female genitalia in ventral view. a: labium; b: prosternal apophysis; c: last visible abdominal ventrite (female); d: internal reproductive tract; e: left gonocoxites and laterotergite IX; f: spermatheca. 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.