Belonuchus xanthomelas Solsky, 1868

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 68-71

Belonuchus xanthomelas Solsky, 1868

Figs. 6c–e , 16m , 19n , 24b , 32b

Belonuchus xanthomelas Solsky, 1868: 139 .

Philonthus iteratus Sharp, 1887: 788 , new synonymy. Belonuchus iteratus comb. nov. ex Philonthus ( Chani-Posse et al. 2018b) .

Total body length in males 8.60 mm (range 7.4–10.1 mm), in females 8.56 mm (range 7.0– 9.5 mm). Black on head, antennae, mandibles, pronotum, scutellum, part of sterna or all sterna (see variability), and visible abdominal segments 5–6 (except anterior border that is reddish). Reddish on mouthparts, elytra, legs, visible abdominal segments 1–4 and anterior border of fifth. Genital segment pale.

Head: transverse; ratio length/width in males 0.82 (range 0.75–0.91), in females 0.89 (range 0.85–0.94). Dorsal surface with sulcate longitudinal midline visible in anterior half of head; front moderately foveate between antennal insertions. Eyes slightly less than 0.5 times the cephalic lateral length, slightly protruding laterally. Antennomere 4 elongate, 5 as long as wide, 6–10 transverse. Ratio mandibular length/cephalic length in males 1.11 (range 0.95– 1.32), in females 0.84 (range 0.78–0.89); males with mandibles notably expanded at base, each with two clearly separated teeth, middle tooth slightly longer than basal tooth; mandibular channel well developed, with external margin clearly visible, internal margin carinate at base, extending forwards like impressed line beyond of level of middle tooth. Apical palpomere of maxillary and labial palpi longer than 1.25 times, but less than 1.5 times, the preapical palpomere. Ratio cephalic width/pronotal width in males 1.18 (range 1.10–1.27), in females 1.06 (range 1.02–1.09).

Thorax: each dorsal row of pronotum with five punctures; ratio length/width of pronotum in males 1.14 (range 1.07–1.19), in females 1.19 (range 1.16–1.23); ratio anterior width/posterior width of pronotum in males 1.09 (range 1.05–1.14), in females 1.06 (range 1.03–1.09). Scutellum with punctures slightly denser than on elytra, where are moderately dense. Prosternum transversally carinate next to anterior margin and delimited blackwards by an indistinct impressed line. Intercoxal process of mesoventrite shield-shaped; transverse discal ridge well developed, broadly V-shaped, meeting margin of intercoxal process laterally. Profemur of males without discernible internal margin, only near apex with five to six aligned, moderately large spines; external margin with row of spines only in anterior third and not extending until apex, spines at center of row bigger than spines at sides, and also bigger than apical spines of internal margin. Posterior legs of males and females without modifications. Tarsomeres flattened dorsally.

Abdomen: visible tergites 1–3 with posterior basal transverse carina well developed; adjacent area moderadately depressed, with dense wide-superficial punctures, combined with fine punctures; density of wide-superficial punctures decreasing toward apex in tergites 1–3; 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-superficial punctures decreasing in density toward apex; parts of 5–6 visible sternites with fine punctures. Male pregenital sternite moderately emarginate, emargination broadly rounded ( Fig. 16m ). Male genital sternite short (2.42 times longer than wide), very asymmetrical, anterior portion occupying 32% and posterior portion 68% of its length, apical emargination moderately deep ( Fig. 19n ). Abdominal styli slender.

Aedeagus: length 1.0 mm; cone shaped, although narrower at base than previous species of this group; apex very acute; basal half moderately wider than apical half, but in lateral view, basal half is notably wider than apical half; internal sac visible ( Fig. 24b ).

Variability. In addition to the variation in measurements and ratios indicated in the description, and those related to sex and size of specimens, it was noted that the sulcate longitudinal midline of head is more distinct behind the middle of head and the apical antennomere may be paler than the previous ones. The main variation is in the color of ventral part of the thorax, which can be reddish, brown, dark brown or black in some parts; only in the analyzed syntypes of B. iteratus the entire ventral part of thorax is reddish (the specimens are possibly teneral), in the rest of specimens at least the central areas of the sterna always appear darker than at sides, although there are no clear limits, but both colors are mixed (reddish with dark); at most, the complete sterna and even part of legs (coxae, trochanters and femora) are blacker or darker brown, although the legs do not become darker than brown. The fifth visible abdominal segment generally has less than 1/4 anterior reddish and the rest black, but in some specimens this segment can be almost all black (although it can merely appear this way due to a more contracted abdomen) and the reddish part is never larger than 1/4 of the segment length.

Taxonomic comments. Four syntypes of Philonthus iteratus deposited in the NHM (three males and one female), which are possibly teneral (or are a variation in the light color of the sterna of the thorax), were reviewed. They are the only ones with a reddish sternum, devoid of dark to black spots described in the variability. Furthermore, the male specimen glued to a plate along with a female specimen, which includes the handwritten word “type,” is the only one with six punctures in each dorsal row of the pronotum instead of five as is characteristic of B. xanthomelas . Despite these differences, it is proposed that P. iteratus is a junior synonym of B. xanthomelas because their main diagnostic structures are the same, such as the shape and size of the aedeagus, the male genital and pregenital sternites, the mandibles expanded at base, the very long and numerous spines in the anterior tibiae of the males, the first three visible abdominal tergites with few wide superficial punctures limited to the weak depressions and generally the same pattern of body coloration. Belonuchus xanthomelas could be confused with B. basiventris , and the characters that distinguish them have been provided in the taxonomic comments of the latter species.

The type material of B. xanthomelas was not studied, but the information in the original description ( Solsky 1868), Sharp’s additional information (1885) and the congruent identification of diagnostic characters between our studied specimens and some photos ( Fig. 6d ; NHM, shared by M. Chani Posse) of specimens analyzed by Sharp (1885) in the Biologia Centrali Americana were considered sufficient to ensure the correct identification of this species, as well as the synonymy here proposed.

Type material examined from B. iteratus (three males, one female): Lectotype (male, NHM) and one paralectotype (female, NHM) glued in the same plaque: “ Philonthus iteratus Type D.S. Villa Lerdo, Durango, Höge / Villa Lerdo, Durango, Höge / B.C.A.I.2. Philonthus iteratus, Sharp / Sharp Coll. 1905-313 / Belonuchus iteratus ( Sharp, 1885) det. Chani Posse et al. 2018 / Lectotype Philonthus iteratus Sharp, 1887 , Márquez &Asiain des. 2022”. Paralectotypes: “Villa Lerdo, Durango, Höge / Philonthus iteratus, Sharp / Sharp Coll. 1905-313” (m 2, NHM). Additional material examined of B. xanthomelas (18 males, 21 females): Mexico: Baja California Norte: “Ensenada, 1-VI-34/ Collection of H. Leech” (11, FMNH). Hidalgo: Singuilucan, Matías Rodríguez, N20°3.734’, W98° 33.136’, 2740 m, bosque de pino-encino, en troncos con hongos, 8-IV-2007, J. Asiain y J. Márquez cols.” (1, CC-UAEH). “Singuilucan, Los Mirasoles, N19°59.460’, W98° 29.460’, 2620 m, bosque de pino-encino perturbado, en maguey podrido, 22-X-2002, J. Asiain y J. Márquez cols.” (1, CC-UAEH). “Zempoala, Mina de San Juan Tepemazalco, N19°54’, W98°43’, 2600 m, bosque de encino, en nopales podridos, 10-IX-2002, J. Márquez col.” (1, CC-UAEH). Michoacán: “ 2 km S de Patzcuaro, bosque de pino perturbado (eucaliptos), 2050 m, en maguey podrido, 21-IX-2001, J. Márquez col.” (5, MAAS). Morelos: “Mexicapa, bosque de pino, NTP-80 (calamar), zona 2, 25-IV-1993, A. Soria, C. Cabello y E. Córdoba cols.” (1, MAAS). “Tlayacapan y Tlalnepantla camino a San José de los Laureles, cultivo temporal, en nopales podridos, 15-VIII-1998, R. Toledo y J. Márquez cols.” (2, MAAS). “Tlayacapan, San José de los Laureles, localidad 3, bosque mesófilo de montaña perturbado, NTP-80, II-1996, J. Márquez col.” (2, MAAS). Same data, except: “localidad 1, bosque de pino-encino, III-1996, K. Villavicencio y J. Márquez cols.” (2, MAAS). Same data, except: “localidad 3, bosque mesófilo de montaña perturbado, J. Márquez col.” (3, MAAS). “Tlayacapan, San José de los Laureles, localidad 2, bosque pino, NTP-80, IV-1995, K. Villavicencio y J. Márquez cols.” (1, MAAS). Same data, except: “ II-1996, J. Márquez col.” (1, MAAS). Same data, except: “ I-1996, J. Márquez col.” (1, MAAS). “Tlayacapan, San José de los Laureles, bosque mesófilo de montaña, localidad 3, 15-VIII-1998, en troncos caídos, R. Toledo y J. Márquez cols.” (1, MAAS). “Tlayacapan, Santa Catarina, selva baja caducifolia y huertos, en hojarasca, 16-VIII-1998, J. Márquez y R. Toledo cols.” (1, MAAS). Veracruz: “Las Vigas, Reserva Ecológica San Juan del Monte, N19°36’53”, W97°06’27”, bosque de pino, 2449 m, en maguey podrido, 11-VIII-2000, Q. Santiago, J. Márquez y J. Asiain cols.” (3, MAAS). Same data, except: “ 15-IV-1999 ” (1, MAAS). United States: Texas: “Jeff Davis Co., Fort Davis, NW Limpia Canyon, 1-VIII-1969 / FMHD #69-3007, edge of campground area, bait trap, W. S. Suter” (m 1, FMNH).

Group 4: ephippiatus

This group is established for B. ephippiatus ( Say, 1830) ( Fig. 6f ) and B. moroni Márquez, Asiain & Navarrete-Heredia, 2018 ( Fig. 6g ). These species have been recently reviewed by Márquez et al. (2018), so in this work they are only included in the proposal of species groups and in the identification key. Additionally, the diagnostic characters are given that allow easy recognition from other species or groups of species.

Diagnosis of the ephippiatus group: head oval and widened posteriad ( Figs. 6f, g ); without temporal carina; eyes very small, clearly less than 0.5 times the cephalic lateral length; antennomeres 5–10 clearly transverse and bigger than apical antennomere; mandibles not expanded at base but with striations, basal tooth not discernible, left mandible with two middle teeth very close to each other forming a cavity like a C, right mandible with only one middle tooth; intercoxal process of mesoventrite ( Fig. 11h ) strongly converging apically to form an acute and slightly raised apex; transverse discal ridge weakly developed toward sides and well developed at center, where has an apex similar to that of intercoxal process; with a short longitudinal carina near to anterior margin (similar to that of B. cariniventris ); profemur with two rows of spines, both males and females, with a similar arrangement as on metafemur ( Fig. 13g ), space between rows of spines of metafemur with conspicuous microsculpture like wavy lines; tarsomeres of all legs robust and with a median longitudinal groove dorsally ( Fig. 13–l ); visible abdominal tergites 1–3 with posterior basal transverse carina well developed, visible tergite 4 also with posterior basal transverse carina, although can be incomplete at center; visible tergites 1–5 with coarse meshed microsculpture in anterior third contrasting with remainder of its surface, where it is like wavy lines; visible abdominal sternites 1–5 with similar pattern of microsculpture as on tergites, but covering almost half of its length; with coarse setae on abdominal segments; aedeagus with reduced paramere that is placed slightly basad midlength of aedeagus, apex subacute ( Figs. 24c, d ).

Key to Mexican species of Belonuchus of the ephippiatus group

1 Elytra black; sulcate longitudinal midline of head slightly visible; mandibles longer than head (1.04–1.20 times); apical palpomere of maxillary palpi notably longer than preapical palpomere (1.25–1.35 times); male pregenital sternite with U-shaped emargination at posterior margin ( Fig. 16a ); male genital sternite slender and with sides nearly parallel ( Fig. 19p ); aedeagus as in Fig. 24d.................................................................................... B . moroni

- Elytra reddish; sulcate longitudinal midline of head clearly visible; mandibles shorter than head or almost as long as head (0.82–1.06 times); apical palpomere of maxillary palpi slightly longer than preapical palpomere (1.00–1.25 times); male pregenital sternite with V-shaped emargination at posterior margin ( Fig. 16n ); male genital sternite widened toward anterior third ( Fig. 19–o ); aedeagus as in Fig. 24c............................................................. B . ephippiatus

Group 5: arizonicus

Included species: B. cifuentesi Rodríguez & Navarrete-Heredia, 2016 , B. dichrous Erichson, 1840 , and B. flavipennis Solsky, 1870 .

Diagnosis of the arizonicus group: head with temporal carina ( Figs. 9d–e ); mandibles not expanded at base, shorter than head in both sexes ( Figs. 7a, c, e ); pronotum with variable number of punctures in each dorsal row, generally less than five; metatrochanters in both sexes without modifications; metafemora in both sexes with two rows of spines; tarsomeres rather robust and flattened dorsally; color body variable; aedeagus with fused paramere, well-developed, slender and long ( Figs. 24e–g ).

Key to Mexican species of Belonuchus of the arizonicus group

1 Pronotum reddish; first five visible abdominal segments black (except posterior border of fifth), remaining segments reddish ( Fig. 7c ); each dorsal row of pronotum with three punctures; male genital sternite moderately elongate (2.89 times longer than wide) and very asymmetrical ( Fig. 20b ); aedeagus as in Fig. 24f. ....................................... B . dichrous

- Pronotum black; all abdominal segments black or first two visible segments reddish and remaining segments black ( Figs. 7a, d, e ); each dorsal row of pronotum with four punctures; male genital sternite longer or shorter than in previous species and slightly asymmetrical; aedeagus not exactly as above............................................................... 2

2(1) Only elytra reddish, remaining body black ( Figs. 7d, e ); smaller size (length 10.4–12.0 mm); male genital sternite short (2.21 times longer than wide) ( Fig. 20c ); aedeagus as in Fig. 24g .......................................... B . flavipennis

- Elytra, legs and first two visible abdominal segments reddish ( Fig. 7a ); bigger size (length 11.0– 13.4 mm); male genital sternite very elongate (3.28 times longer than wide) ( Fig. 20a ); aedeagus as in Fig. 24e........................... B . cifuentesi

Figures

FIGURE 6. Dorsal view of males (except figure c) of: a) Belonuchus longitarsus (holotype), b) B. rufiventris, c) B. iteratus (male lectotype and female paralectotype, NHM©), d) B. xanthomelas (NHM©, Biologia Centrali-Americana), e) B. xanthomelas, f) B. ephippiatus, g) B. moroni (paratype). Scale bars = 2.5 mm.

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 13. Ventral view of the left posterior leg of males of: a) B. trochanterinus, b) B. tenuistylus, c) B. zunilensis, d) B. rufipennis, e) B. mixtecus, f) B. pollens, g) B. ephippiatus, h) B. aenigmaticus, i) B. iridescens, j) B. viridipennis. Tarsomeres of posterior leg of males of: k) B. colon, l) B. ephippiatus. Yellow ovals: median longitudinal groove.

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 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.