Balligratus, 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 : 102-103

Balligratus gen. nov.

Type species: Balligratus humerangulus sp. nov.

Description. Total body length ranging from 4.0 to 6.9 mm. Proportions quite variable, from slender and narrow to short and plump ( Figs. 2 , 5 , 7 and 9 ). Integument smooth, without punctation. Head, pronotum and elytra brunneopiceous to nigropiceous, with or without a slight metallic sheen; legs and cephalic appendages uniformly flavotestaceous to rufotestaceous ( Fig. 1 b).

Head broad, with short frontal sulci, no supraorbital carinae, neck constriction hardly visible on the upper side; temporae short and flat; eyes relatively small, convex but not bulging; labrum trapezoidal; mandibles moderately elongate. Labium with a well-developed, acute mentum tooth ( Figs. 3 a, 6g, 8a and 10a). Head setation: two pairs of supraorbital setae; two clypeal setae close to the apicolateral angles of the clypeus; six setae along the anterior margin of labrum; two short labial setae at base of the mentum tooth; two long submentum setae, one at each side of the submentum; ligula with two setae. Maxillary and labial palpi almost glabrous, except for a sparse micropubescence on the last palpomere, visible at high magnification ( Figs. 3 a, 6g, 8a and 10a); two setae on the inner ridge of the penultimate labial palpomere; last maxillary palpomere slender, fusiform, gradually narrowed apically. Antennae slender, pubescent from the 4th segment onwards; 1st to 3rd antennomeres glabrous, the 1st with one subapical seta, the 2nd and 3rd with a ring of apical setae.

Pronotum broader than long, strongly constricted basally, with effaced hind angles; sides slightly arcuate to straight in basal half, never sinuate; posteriolateral depression shallow; lateral groove narrow. Disc convex, divided by a longitudinal sulcus. Only one pair of fixed lateral setae on the pronotum, anterad the middle of the lateral margin.

Elytra oval, convex; humeri constricted and narrowly rounded; apex markedly truncate. Striae complete, moderately to sharply impressed, without punctation; intervals flat to slightly convex; scutellar striole short, at base of the first interval. Elytral setation: parascutellar setiferous puncture present; three fixed setae inserted in small punctures on the third elytral interval, seta 1 adjoining the 3rd stria, seta 2 adjoining the 2nd stria, seta 3 located near the apex, adjoining the 2nd stria. The 13 lateral umbilicate setae in the 9th interval are divided into three groups: 5 setigerous punctures in the humeral area, 1 puncture in the median area (rarely 2), and 7 punctures in the subapical area (rarely 6). Two apical setae, one close to the apex of the 2nd stria, the other near the apex of the 7th stria.

Metathoracic wings reduced. Metepisternum quadrate, lateral and anterior margins about equal in length. Abdominal ventrites glabrous; last visible ventrite arcuate to medially emarginate ( Figs. 3 c–d, 6a, 8c and 10c), with one pair of setae in the male, two pairs in the female.

Legs slender, without remarkable sculptural traits except a longitudinal sulcus along the dorsal surface of the pro-, meso- and metatibiae; protibial antennal cleaner with two clip setae; tarsi dorsally glabrous; protarsomeres 1 to 3 slightly dilated in the male, with an adhesive vestiture on their ventral face; tarsal claws smooth.

Male genitalia ( Figs. 3 e–i, 6b–f and 8d–h): median lobe robust, massive, slightly swollen at middle; median lobe apex short to slightly elongate, diversely spatulate in dorsal view; internal sac complexly folded, broadly squamose, without sclerotized structures. Parameres glabrous; left paramere large, more or less ovoid; right paramere small, narrow, with a hook-shaped basal process and bifid apex. Ring sclerite elongate- ovate with a subtriangular handle-like extension.

Female genitalia ( Figs. 4 and 10 c–e): gonocoxite 1 or gonosubcoxite subtriangular, longer than broad, with five long ensiform setae in a row near apical margin; gonocoxite 2 or apical gonocoxite moderately falcate, longer than broad, with two ventral preapical nematiform setae in a small fossula, one dorsal seta and two dorsolateral ensiform setae inserted near the external ridge, exceeding it externally. Laterotergite IX broad, weakly sclerotized, spinose near apical margin. Bursa copulatrix broad, tubular, invaginated at its distal end where it communicates with common oviduct; length of spermathecal duct variable; spermatheca bipartite, with basal bulb narrower than apical bulb; spermathecal gland globose; spermathecal gland duct slender, longer than spermathecal bulbs, attached to spermatheca at base of spermathecal apical bulb.

Etymology. Combination of the Latin adjective gratus, “grateful to”, and the surname of George E. Ball.

Distribution. Based on the current state of knowledge, the distribution of Balligratus seems to be restricted to Ecuador and southern Colombia ( B. gracilis sp. nov. was found very close to the Ecuador – Colombia border), on the Pacific slope of the Western Cordillera and on the Amazonian slope of the Eastern Cordillera from 1° N to 3° S, at elevations ranging from 1,200 to 3,600 m, though most collections have been made between 1,800 and 3,200 m.

Way of life. Adults of this genus are most frequently found in leaf litter or under rotten logs in montane pluvial forests.

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 2. Balligratus humerangulus sp. nov., male holotype, habitus in dorsal view. 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 5. Balligratus gracilis sp. nov., male holotype, habitus in dorsal view. Scale bar: 1 mm.

FIGURE 7. Balligratus brevis sp. nov., male holotype, habitus in dorsal view. Scale bar: 1 mm.

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.