Belonuchus basiventris ( Sharp, 1885 )

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 62-63

Belonuchus basiventris ( Sharp, 1885)

Figs. 5e, f , 16k , 19j , 23g , 30b

Philonthus basiventris Sharp, 1885: 418 . Belonuchus basiventris comb. nov. ex Philonthus (Jiménez-Sánchez et al. 2000) .

Total body length in males 9.31 mm (range 8.0– 10.2 mm), in females 9.2 (range 8.4–9.8 mm). Black on head, pronotum, scutellum, ventral surface of thorax, posterior coxae, first visible abdominal segment, anterior 2/3 of second, posterior 2/3 of fifth, entire sixth and abdominal styli. Reddish on elytra, legs (except posterior coxae), posterior 1/3 of second visible abdominal segment, entire third and fourth segments, anterior 1/3 of fifth segment and genital segment.

Head: oval shape, dorsally slightly convex, wider than long (ratio in males 0.80, range 0.76–0.84, in females 0.88, range 0.81–0.92). Dorsal surface with microsculpture like wavy lines fainty visible near front, along margin of eyes and base of antennae; punctures less dense than in majority of species, with similar distribution as in other species; sulcate longitudinal midline faintly visible only at front; front weakly foveate between antennal insertions. Eyes nearly 0.5 times the cephalic lateral length, slightly protruding laterally. Antennomere 1 as long as antennomeres 2–3 combined, antennomeres 4–5 elongate, 6 as long as wide, 7–10 transverse. Mandibles as long as head in males (ratio 1.0, range 0.90–1.12), and shorter than head in females (ratio 0.84, range 0.77–0.88); mandibles of males widened at base, in females not widened at base; each mandible with two well separated teeth (basal and middle) of similar size; mandibular channel well developed, external margin carinate, internal margin like impressed line extending forward slightly beyond level of middle tooth. Apical palpomere of maxillary palpi 1.5 times longer than subapical palpomere. Apical palpomere of labial palpi slightly longer than preapical palpomere. Males with head 1.13 times wider than pronotum (range 1.04–1.19), in females 1.03 times (range 1.00–1.04).

Thorax: pronotum smooth, without visible microsculpture; each dorsal row with five punctures; pronotum slightly longer than wide (ratio in males 1.15, range 1.11–1.20, in females 1.17, range 1.14–1.20) and almost as wide at anterior corners as at posterior corners (ratio in males 1.04, range 1.00–1.08, in females 1.0, without variation). Scutellum with punctures slightly denser than punctures on elytra, punctation of elytra less dense and surrounded by brown coloration, which contrasts with reddish smooth surface. Prosternum with area near to anterior margin slightly elevated transversally and without posterior constriction or line. Intercoxal process of mesoventrite shieldshaped, but sides toward apex not as straight as in many species; transverse discal ridge moderately developed, broadly V-shaped, not touching margin of intercoxal process laterally. Profemur of males without internal margin or only discernible near apex, there with five to six large aligned spines; external margin with row of spines only in anterior third, not extending until apex, middle spines longer than lateral spines, and longer than apical spines of internal margin. Posterior legs of males and females without modifications. Tarsomeres flattened dorsally, but slightly visible because they are somewhat narrow.

Abdomen: first two visible tergites with posterior basal transverse carina well developed, but in visible tergite 3, posterior basal transverse carina diffuse or not completely developed; adjacent area moderately depressed, with wide-superficial punctures moderately dense combined with fine punctures; posterior half of visible tegites 1–3 with less dense wide-punctures; visible tergite 4 with punctures as on previous tergites; visible tergites 5–6 only with fine punctures. Visible sternites 1–3 with wide-superficial punctures combined with fine punctures on entire surface; visible sternites 4–5 with wide punctures that are less dense posteriorly; sixth visible sternite only with fine punctures. Male pregenital sternite with distinct, broadly U-shaped or V-shaped emargination at posterior margin ( Fig. 16k ). Male genital sternite short (2.35 times longer than wide), very asymmetrical, anterior portion occupying 33% and posterior portion 67% of its length, apical emargination deep ( Fig. 19j ). Abdominal styli slender.

Aedeagus: length 1.0 mm; cone-shaped, sides not as homogeneously narrowed toward very acute apex; basal half moderately wider than apical half, latter gradually narrow toward apex; internal sac indistinctly visible ( Fig. 23g ).

Variability. Great variation was observed in the extension and intensity of the black or dark color of first two visible abdominal segments; lighter portion of segment 2 and entire segment 3 are brown (darker than elytra) rather than reddish; brown coloration around punctures of elytra is not present in all specimens; prosternum may be reddish in anterior half and black or brown in posterior half, all brown or all black; posterior coxae can be from totally black to reddish-brown; posterior basal transverse carina of visible tergite 3 variably developed, but always less than in two previous tergites.

Taxonomic comments. This species can be confused with B. xanthomelas , but B. basiventris has the first two visible abdominal segments mostly black, with some minor reddish portions, entire ventral part of thorax black, male pregenital sternite remarkably emarginate at posterior margin like extended U-shaped, and aedeagus with basal half moderately wider than apical half ( Figs. 16k , 23g ). Conversely, B. xanthomelas has the first four visible abdominal segments and anterior border of fifth reddish, ventral surface of thorax not completely black, because the ventral surface of thorax (sterna) are black at center and peripheral parts are reddish or even entire sterna can be reddish, male pregenital sternite moderately emarginate at posterior margin and aedeagus narrower at base, apex very acute, in lateral view, it is notably wider in basal half ( Figs. 16m , 24b ).

The syntypes of this species were not studied, but we analyzed some photos of these specimens ( Fig. 5e ; NHM, shared by M. Chani Posse), which together with the information of the original description ( Sharp 1885) allowed us to identificaty this species.

Material examined (20 males, 13 females): Mexico: Hidalgo: “ Huasca de Ocampo, San Miguel Regla, bosque Las Truchas , bosque de encino, 2073 m, N20°13’0.3”, W98°33’28.6”, en hojarasca cernida, 14-IV-2007. J. Márquez y J. Asiain, cols.” (1, CC-UAEH) . Morelos: “camino a Mexicapa , bosque mesófilo de montaña perturbado, NTP-80 (calamar), zona 6, 6-VI-1993, A. Soria y E. Córdoba cols.” (3, MAAS) . “ Ocuilan, camino a Mexicapa , bosque de pino, trampa 1, VIII-1993, J. Márquez col.” (2, MAAS) . Same data, except: “ VI-1993 ” (5, MAAS) . “ Tlayacapan , en detritos de A. mexicana , 20-VII-1992, J. Márquez col.” (2, MAAS) . “ Tlayacapan , selva baja caducifolia, zona 4, NTP-80, IV-1996, J. Márquez y K. Villavicencio cols.” (2, CC-UAEH) . “ Tlayacapan, San José de los Laureles , en hojarasca, 28-V-2000, J. Márquez y J. Asiain cols. “ (18, MAAS) .

Figures

FIGURE 5. Dorsal view of males (except figure g) of: a) B. mixtecus (holotype), b) B. pollens (syntype, NHM©), c) B. pollens, d) B. rufipennis, e) B. basiventris (syntype, NHM©), f) B. basiventris, g) B. connexus (female holotype of B. xanthopus, synonym of B. connexus, shared by A. Kovalev©), h) B. connexus. Scale bars = 2.5 mm.

FIGURE 16. Male pregenital sternite of: a) Belonuchus moroni, b) B. dichrous, c) B. flavipennis, d) B. aenigmaticus, e) B. nigerrimus, f) B. juanmorronei, g) B. godmani, h) B. magnistylus, i) B. trochanterinus, j) B. rufipennis, k) B. basiventris, l) B. connexus, m) B. xanthomelas, n) B. ephippiatus, o) B. optatus.

FIGURE 19. Male genital sternite of: a) Belonuchus tepoztecus, b) B. trochanterinus, c) B. zunilensis, d) B. bidens, e) B. erichsoni, f) B. jalappensis, g) B. mixtecus, h) B. pollens, i) B. rufipennis, j) B. basiventris, k) B. connexus, l) B. longitarsus, m) B. rufiventris, n) B. xanthomelas, o) B. ephippiatus, p) B. moroni. Scale bars = 0.5 mm.

FIGURE 23. Ventral (left) and lateral (right) view of the aedeagus of: a) Belonuchus bidens, b) B. erichsoni, c) B. jalappensis, d) B. mixtecus, e) B. pollens, f) B. rufipennis, g) B. basiventris, h) B. connexus (at center, detail of the apex of the median lobe), i) B. longitarsus (at center, detail of the apex of the median lobe). Scale bar = 0.5 mm (all figures).

FIGURE 24. Ventral (left) and lateral (right) view (except e) of the aedeagus of: a) Belonuchus rufiventris, b) B. xanthomelas (at center, detail of the apex of the median lobe), c) B. ephippiatus, d) B. moroni, e) B. cifuentesi (left: detail of paramere, right: ventral view; from Rodríguez and Navarrete-Heredia, 2016), f) B. dichrous, g) B. flavipennis, h) B. aenigmaticus, i) B. iridescens, j) B. nigerrimus, k) B. optatus, l) B. platypterus. Scale bar = 0.5 mm (all figures, except e).

FIGURE 30. Geographical distribution in Mexico and Guatemala of: a) Belonuchus abnormalis, B. bidens and B. platypterus; b) B. basiventris and B. jalappensis.