Belonuchus dichrous Erichson, 1840

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 72-73

Belonuchus dichrous Erichson, 1840

Figs. 7b, c , 9d, e , 11i , 16b , 20b , 24f , 32b

Belonuchus dichrous Erichson, 1840: 420 .

Total body length in males 11.15 mm (range 9.40–12.90 mm), in females 11.6 mm (range 9.50–13.70 mm). Black on head, antennomeres 1–9, mandibles, neck, first four visible abdominal segments and anterior 2/3 of fifth segment. Reddish on maxillary and labial palpi, last two antennomeres, elytra, scutellum, sterna, legs and from posterior third of fifth visible abdominal segment to sixth segment. Posterior legs dark-brown.

Head: slightly transverse, ratio length/width in males 0.92 (range 0.91–0.95), in females 0.90 (range 0.88–0.92), sides and posterior corners somewhat convex; with well developed, oblique temporal carina from dorsal to ventral surface ( Figs. 9d–e ). Dorsal surface with punctures distributed as in majority of species, but less dense; sulcate longitudinal midline visible in anterior half of head; front little to moderately foveate between antennal insertions. Eyes small, 0.4 times the cephalic lateral length, not protruding at sides. Antennomere 4 elongate, 5–10 transverse. Mandibles shorter than head (ratio in males 0.76, range 0.71–0.79; in females 0.73, range 0.68–0.79); with microsculpture like wavy lines near its base, left mandible with two middle teeth very close to each other (similar as in B. ephippiatu s), right mandible with a middle tooth and in some specimens with another very small tooth beneath first; both mandibles without visible basal tooth; mandibular channel moderately developed, with external margin not carinate and internal margin carinate, extending forward near level of most apical tooth and then is lost. Apical palpomere of maxillary and labial palpi nearly 1.25 times longer than preapical palpomere. Ventral surface of head with very fine and sparse punctures. Head wider than pronotum (ratio in males 1.21, range 1.17–1.26; in females 1.18, range 1.15–1.22).

Thorax: pronotum with microsculpture like wavy lines more distinct than on head; each dorsal row of pronotum with three punctures, first one very close to anterior margin and following two not exceeding beyond anterior half; sublateral punctures sparser than in majority of species; pronotum slightly longer than wide (ratio in males 1.07, range 1.03–1.10; in females 1.10, range 1.03–1.15) and wider at anterior corners than at posterior corners (ratio in males 1.21, range 1.20–1.23; in females 1.21, range 1.12–1.27). Scutellum and elytra with fine and dense punctures. Prosternum without an elevated zone near anterior margin. Intercoxal process of mesoventrite scutellum-shaped, apex acute with a small pick; transverse discal ridge notably less curved posteriad than margin of intercoxal process, slightly acute apically, meeting margin of intercoxal process laterally, with a faint midlongitudinal carina reaching until anterior margin (similar to the carina observed in B. cariniventris and B. ephippiatus ) ( Fig. 11i ). Profemur of both sexes with two rows of spines, external row initiating distant from its base and ending before apex, internal row developed almost on all its length; both rows with small, black spines. Metafemur in both sexes with two rows of spines well aligned on almost all its length, spines slightly separated and bigger than on profemur; internal area between both rows with conspicuous microsculpure like wavy lines. Metatibiae with black spines, which contrast with the reddish color of the tibial surface. Tarsomeres somewhat robust (not as robust as in ephippiatus group) and flattened dorsally.

Abdomen: entire abdomen with very dense, large and short setae; first two visible tergites with straight posterior basal transverse carina and third tergite with zig-zagging posterior basal transverse carina or at least not straight; adjacent area narrow and weakly depressed; both tergites and sternites (especially 3 and 4), with coarse meshed microsculpture in anterior 1/3 to 1/2 of its length, then fading until there is only finer microsculpture like wavy lines (as in ephippiatus group). Visible sternites 1–5 with conspicuous sinuous posterior basal transverse carina. Male pregenital sternite weakly emarginate at posterior margin ( Fig. 16b ). Male genital sternite moderately elongate (2.89 times longer than wide), very asymmetrical, anterior portion occupying 23% and posterior portion 77% of its length, apical emargination very deep ( Fig. 20b ). Abdominal styli slender, with external margin slightly curved and internal margin straight.

Aedeagus: length 1.2 mm; oval shape in basal half and elongate in apical half; fused paramere as long as 1/2 of aedeagus length; apex somewhat convex, not acute; in lateral view, apex looks slightly directed toward ventrad; in ventral view, basal half notably wider than apical half, not as evident in lateral view; internal sac not visible ( Fig. 24f ).

Variability. In addition to the variation indicated in the description regarding measurements and ratios, some specimens have the apical antennomere reddish and the preapical antennomere black; right mandible with the first middle tooth very small until not discernible, in the latter case only one middle tooth is visible; visible tergite 3 with posterior basal transverse carina variably developed, in part due to the coarse meshed microsculpture that covers it.

Taxonomic comments. Species in the arizonicus group share several characteristics with the ephippiatus group, suggesting that they could turn out as sister groups in a future study that considers all the species of the genus. Among these characteristics are the small eyes on a somewhat robust head, mandibles shorter than head, teeth of left mandible, the arrangement of the two rows of spines at anterior and posterior tibiae of both sexes, the development of two types of microsculpture on each abdominal segment and the robust tarsomeres. The ratio of antennomeres is somewhat similar, but not the same, the coarse microsculpture at base of mandibles in B. dichrous also resembles the striated mandibles of the ephippiatus group. Belonuchus dichrous is distinguished from B. cifuentesi and B. flavipennis by having the pronotum reddish as the elytra and only the posterior border of fifth visible abdominal segment and entire sixth segment reddish. While B. cifuentesi has the pronotum black and the elytra reddish, with first two visible abdominal segments reddish and the rest black. Unlike B. dichros , B. flavipennis has only the elytra reddish and the rest of the body black (except the anterior border of sixth visible abdominal segment that is reddish).

The syntypes of this species were not studied, but we consider that the information of the original description ( Erichson 1840), the additional information given by Sharp (1885) and the congruent identification of diagnostic characters between the studied specimens and some photos ( Fig. 7b ; NHM, shared by M. Chani Posse) of specimens depicted by Sharp (1885) in the Biologia Centrali-Americana, are sufficient to be sure of the correct identification of this species.

Material examined (13 males, 15 females): Mexico: Hidalgo: “ Huehuetla, Rio Blanco , 588 m, UTM (WG- 384), 14594809 E, 2257303 N, bosque tropical perennifolio, NTP-80 (calamar) 1 a 30-V-2010, C. Berriozábal col.” (1, CC-UAEH) . “La Misión, Los Naranjos, Palo Hueco , bosque mesófilo de montaña, 1216 m, N21°08’06”, W98°05’02”, coprotrampa, del 10 al 24-III-2011, J. Márquez col.” (1, CC-UAEH) . “ Molango, Acuatitlán , bosque mesófilo de montaña, 1715 m, N20°45’38.4”, W88°42’50.7”, tronco podrido de colorín, 30-IX-2011, J. Márquez col.” (1, CC-UAEH) . “ Tepehuacán de Guerrero, Otongo , 650 m, ex carrion trap, 2-march-1981, M. A. Morón ” (2, IEXA) . Puebla: “ Xicotepec de Juárez, Cañada de Patla , bosque mesófilo de montaña perturbado, 11-XI-1994, en tronco caído, J. Márquez col.” (2, MAAS) . Same data, except: “ 5-I-1995 ” (1, MAAS) . Veracruz: “ Córdoba, Ojo de Agua , selva mediana subcaducifolia, 1127 m, en tronco caído, 23-X-1998, R. Toledo, G. Flores, Q. Santiago y J. Márquez cols.” (1, MAAS) . Same data, except: “en lima podrida, 24-I-1999, Q. Santiago, J. Asiain y J. Márquez cols.” (1, MAAS) . “ Totutla, Mata Oscura , 1 km S de Zacuapam, selva mediana subcaducifolia, 921 m, café podrido, 16-IV-1999, J. Asiain, Q. Santiago y J. Márquez.” (3, MAAS) . Same data, except: “ 19-III-1999, J. Asiain, G. Rodríguez, Q. Santiago y J. Márquez cols.” (1, MAAS) . “ Xalapa, San Antonio Paso del Toro , N19°35´20.3”, W96°50´17.5”, 990 m, selva baja caducifolia, trampa de intercepción de vuelo #1, 4-IV-2015, L. Delgado col.” (3, IEXA) . Same data, except: “ 2-V-2015 ” (2, IEXA) . Same data, except: “ 2 a 30-V-2015, K. Cortés, J. Sulvaran y Q. Santiago cols.” (2, QJSJ; 1, IEXA). Same data, except: “ 30-V a 27-VI-2015 ” (1, IEXA) . “ Xico, San Marcos , N19°25´6.23”, W96°57´58.13”, 1155 m, en lombricomposta de pulpa de café, 6-V-2015, H. Pacheco col.” (1, QJSJ) . Same data, except: “ 21-V-2015 ” (1, QJSJ) . Same data, except: “ N19°24´25.25”, W96°57´31.06”, 1125 m ” (1, QJSJ) . Same data, except: “ N19° 27´56.70”, W96°55´57.31”, 1210 m ” (1, QJSJ) . Same data, except: “ N19°27´56.70”, W96° 55´57.31”, 1210 m, 6-V-2015 ” (1, QJSJ) .

Figures

FIGURE 7. Dorsal view of males (except figures d and f) of: a) Belonuchus cifuentesi (paratype), b) B. dichrous (NHM©, Biologia Centrali-Americana), c) B. dichrous, d) B. flavipennis (female holotype shared by A. Kovalev©), e) B. flavipennis, f) B. iridescens (female holotype shared by A. Kovalev©), g) B. iridescens. Scale bars = 2.5 mm.

FIGURE 9. Dorsal view of males of: a) Belonuchus sp. Q, b) B. cyanipennis (holotype), c) B. godmani. Head of B. dichrous showing the temporal carina (red arrow): d) lateral view (male), e) dorsal view (male). Dorsal view of the mandibles of males of: f) B. platypterus, g) B. viridipennis. Mandibles of Belonuchus sp. Q (male): h) dorsal view, i) ventral view. Antennae of males of: j) B. godmani, k) B. cyanipennis. Scale bars = 2.5 mm.

FIGURE 11. Mesoventrite of males of: a) Belonuchus cariniventris, b) B. oxyporinus, c) B. rufisternus, d) B. tepoztecus, e) B. bidens, f) B. jalappensis, g) B. longitarsus, h) B. ephippiatus, i) B. dichrous, j) B. flavipennis, k) B. platypterus, l) B. juanmorronei, m) B. iridescens. Red arrow: intercoxal process of the mesoventrite, blue arrow: transverse discal ridge, green arrow: longitudinal carina in anterior half.

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 20. Male genital sternite of: a) Belonuchus cifuentesi, b) B. dichrous, c) B. flavipennis, d) B. aenigmaticus, e) B. iridescens, f) B. nigerrimus, g) B. optatus, h) B. platypterus, i) B. juanmorronei, j) B. abnormalis, k) B. pectinipes, l) B. viridipennis, m) Belonuchus sp. Q, n) B. cyanipennis, o) B. godmani. Scale bars = 0.5 mm.

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 32. Geographical distribution in Mexico and Guatemala of: a) Belonuchus cifuentesi, B. connexus and B. pectinipes; b) B. dichrous, B. iridescens and B. xanthomelas.