Belonuchus tenuistylus, Márquez & Asiain, 2022

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 45-46

Belonuchus tenuistylus sp. nov.

http://zoobank.org/NomenclaturalActs/49d6419a-a9ee-4c63-893a-c70f026c193e

Figs. 4a , 13b , 15–l , 18–o , 22f , 28a

Total body length 10.8 mm. Black on head, antennomeres 1–3, borders of mandibles, pronotum, scutellum, posterior half of prosternum, entire sixth and anterior half of fifth visible abdominal segments, and abdominal styli. Reddish on elytra, legs, anterior half of prosternum, posterior half of mesoventrite, entire metaventrite, visible abdominal segments 1–4 and anterior half of fifth. Brown on antennomeres 4–11 and mesoventrite.

Head: transverse, slightly convex at sides and backward; ratio length/width of head 0.73. Dorsal surface with sulcate longitudinal midline visible in anterior half of head; front foveate in a small portion near to anterior margin. Eyes nearly 0.5 times the cephalic lateral length, not protruding laterally. Antennomeres 4–6 elongate, 7–10 almost as long as wide. Mandibles 1.5 times longer than head; each with two widely separated teeth (basal and middle) of moderate size; mandibular channnel with external margin expanded at basal third of its length, leaving a wide space between this and internal margin, which is carinate and ends near level of middle tooth. Apical palpomere of maxillary and labial palpi nearly 1.25 times longer than preapical palpomere. Head 1.29 times wider than pronotum.

Thorax: pronotum with five punctures in the left and seven in the right dorsal row; pronotum slightly longer than wide (ratio 1.1) and almost as wide at anterior corners as at posterior corners (ratio 1.07). Scutellum with punctures slightly denser than on elytra, its margins smooth. Elytra with punctures moderately dense, with fine setae. Prosternum moderately elevated behind anterior margin. Intercoxal process of mesoventrite shield-shaped; transverse discal ridge clearly visible, broadly U-shaped or V-shaped, slightly acute posteriorly, meeting margin of intercoxal process laterally. Profemur with external row of spines initiating a little before half of its length and not reaching apex, and not reaching level of femur where some apical spines of internal margin begin, internal margin only visible in this anterior portion; spines of moderate size, similar to some spines of protibiae. Metatrochanter modified like a small hook that does not exceed 1/4 of length of metafemur, hook curved only near apex ( Fig. 13b ); metafemur without curvature in area of overlap with hook; metatibia straight. Tarsomeres slender, pooly flattened dorsally.

Abdomen: first three visible tergites with posterior basal transverse carina well developed; depressed adjacent area with wide-superficial punctures moderately dense, which are missing or only sparse on remaining surface of these tergites, as well as following tergites, which have fine, sparse punctures. Visible sternites 1–4 with wide-superficial punctures in anterior half, and with fine, sparse punctures on remaining surface, as well as on remaining sternites. Male pregenital sternite weakly emarginate at posterior margin ( Fig. 15–l ). Genital sternite moderately large (2.87 times longer than wide), moderately asymmetrical, anterior portion occupying 33% and posterior portion 67% of its length; apical emargination deep ( Fig. 18–o ). Abdominal styli slender.

Aedeagus: length 1.3 mm; cone-shaped, apex pointed; sides becoming regularly wider from apex to base; basal half notably wider than apical half; internal sac visible ( Fig. 22f ).

Variability. In measurements and ratios, the following variation was observed: total body length in males 10.5 mm (range 9.9–11.2 mm), in females 9.8 mm (range 8.5–10.5 mm); ratio length/width of head in males 0.77 (range 0.65–0.85), in females 0.88 (range 0.86–0.90); ratio mandibular length/cephalic length in males 1.25 (range 1.00–1.43), in females 0.86 (range 0.81–0.92); ratio cephalic width/pronotal width in males 1.23 (range 1.11–1.40), in females 1.06 (range 1.01–1.08); ratio length/width of pronotum in males 1.12 (range 1.03–1.20), in females 1.17 (range 1.12–1.21); ratio anterior width/posterior width of pronotum in males 1.05 (range 1.05–1.08), in females 1 (without variation). Apical antennomere, some times also subapical antennomere, lighter than the preceding ones. Most specimens have five punctures in each dorsal row of pronotum, with a variation of 5:6, 6:5 or as in the holotype. The anterior half of the mesoventrite may be reddish as on its posterior half or darker (brown).

Taxonomic comments. Due to its color pattern, size and modification of the male metatrochanters, this species has been confused with B. trochanterinus in publications reporting the presence of B. trochanterinus in Mexico. The analysis of the holotype of this latter species has made it possible to distinguish them in a simple way because B. trochanterinus has abdominal styli that are very wide apically, while they are slender and elongate in B. tenuistylus , in addition to the differences in the shape of the genital sternite and the aedeagus of both species. Furthermore, B. tenuistylus resembles B. metafemoralis and in the taxonomic comments of this latter species it has been indicated how to distinguish them.

Etymology. The name of this species is a combination of the words “tenuis” and “stylus”, in order to highlight the slender styli of this species that easily separate it from B. trochanterinus .

Type material (18 males, 17 females): Holotype (male, CC-UAEH) : “ México, Morelos, Tlayacapan, San José de los Laureles , camino a Amatlán , N18°58´5”, W99°00´5”, localidad 1, bosque de pino-encino, 1874 m, NTP-80 (calamar), 1 a 30-VIII-1995, J. Márquez col.” Paratypes: Mexico: Morelos: “ Tlayacapan, San José de los Laureles , NTP-80, localidad 1, bosque de pino-encino, X-1995, K. Villavicencio y J. Márquez cols.” (6, CC-UAEH) . Same data, except: “ Octubre-1995 ” (4, MAAS) . Same data, except: “localidad 3, bosque mesófilo de montaña perturbado” (3, MAAS) . “ Tlayacapan , selva baja caducifolia, zona 4, NTP-80, VI-1996, J. Márquez y K. Villavicencio cols.” (1, MAAS) . “ Tlayacapan, San José de los Laureles , camino a Amatlan , N18°58’7”, W99°01’15”, 1783 m, bosque mesófilo de montaña, NTP-80 (calamar), Julio-1995, J. Márquez col.” (2, MAAS) . Same data, except: “bosque de pino y pino-encino, agosto-1995 ” (9, MAAS) . Same data, except: “bosque mesófilo de montaña, septiembre-1995 ” (3, MAAS) . Same data, except: “bosque de pino-encino, octubre-1995 ” (3, MAAS) . Same data, except: “bosque de pino, diciembre-1995 ” (1, MAAS) . Same data, except: “bosque mesófilo de montaña, junio-1996 ” (2, MAAS) .

Figures

FIGURE 4. Dorsal view of males of: a) Belonuchus tenuistylus (holotype), b) B. tepoztecus (paratype), c) B. trochanterinus, d) B. zunilensis (lectotype), e) B. bidens (syntype, NHM©), f) B. bidens, g) B. erichsoni, h) B. jalappensis. Scale bars = 2.5 mm.

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 15. Male pregenital sternite of: a) Belonuchus alternans, b) B. oxyporinus, c) B. tepoztecus, d) B. jalappensis, e) B. iridescens, f) B. platypterus, g) B. cyanipennis, h) B. apiciventris, i) B. linuzensis, j) B. metafemoralis, k) B. rufisternus, l) B. tenuistylus, m) B. bidens, n) B. pollens, o) B. longitarsus.

FIGURE 18. Male genital sternite of: a) Belonuchus altenans, b) B. apiciventris, c) B. cariniventris, d) B. colon, e) B. confusus, f) B. julietitae, g) B. magnistylus, h) B. linuzensis, i) B. metafemoralis, j) B. oxyporimimus, k) B. oxyporinus, l) B. pulcher, m) B. rufisternus, n) B. singularis, o) B. tenuistylus. Scale bars = 0.5 mm.

FIGURE 22. Ventral (left) and lateral (right) view of the aedeagus of: a) Belonuchus oxyporimimus, b) B. oxyporinus, c) B. pulcher, d) B. rufisternus, e) B. singularis, f) B. tenuistylus, g) B. tepoztecus (at center detail of the paramere), h) B. trochanterinus, i) B. zunilensis. Scale bar = 0.5 mm (all figures).

FIGURE 28. Geographical distribution in Mexico and Guatemala of: a) Belonuchus colon, B. tenuistylus and B. trochanterinus; b) B. oxyporimimus, B. pulcher and B. juanmorronei.