Belonuchus mixtecus, Márquez & Asiain, 2022

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 56-57

Belonuchus mixtecus sp. nov.

http://zoobank.org/NomenclaturalActs/341f9562-23cc-447b-82d0-8848b80967cf

Figs. 5a , 13e , 17o, 19g, 23d, 27b

Total body length 12.5 mm. Black on head, antennae, mouthparts, pronotum, scutellum, prosternum, anterior half of mesoventrite, from fifth visible abdominal segment (except 1/4 to 1/5 anterior) to genital segment and abdominal styli. Reddish on elytra, posterior half of mesoventrite, metaventrite, legs, visible abdominal segments 1–4 and anterior 1/4 to 1/5 of fifth.

Head: transverse, ratio length/width 0.65, postero-dorsal area and posterior corners convex. Dorsal surface with sulcate longitudinal midline visible in anterior half of head; front foveate between antennal insertions. Eyes less than 0.5 times the cephalic lateral length, not protruding laterally. Antennomere 2 almost as long as 3, 4–6 elongate, 7 as long as wide, 8–10 transverse. Mandibles very long, 1.75 times longer than head; each with two very close teeth, basal tooth bigger than middle tooth; mandibular channel moderately developed, external margin slightly carinate, internal margin carinate, extending beyond level of middle tooth. Apical palpomere of maxillary and labial palpi almost as long as preapical palpomere. Head 1.23 times wider than pronotum.

Thorax: left dorsal row with seven punctures and right dorsal row with six punctures; pronotum 1.12 times longer than wide and 1.13 times wider at anterior corners than at posterior corners. Scutellum with punctures slightly denser than on elytra, where it is moderately dense. Prosternum slightly elevated transversally before anterior margin. Intercoxal process of mesoventrite shield-shaped; transverse discal ridge well developed, broadly Ushaped, not meeting margin of intercoxal process laterally. Profemur slightly widened toward apex (less noticeable than in B. bidens ); external margin with row of short, dark and dense spines that initiate near base and end at apex where margin is narrow; internal margin with row of spines even shorter (difficult to see), initiating further apicad than external row and reaching apex, where four to six spines are longer than previous spines; with a few spines at base of femur between both rows. Metafemur somewhat widened and flattened in basal half of external surface ( Fig. 13e ); with two rows of spines not clearly aligned at base, where there are some additional spines, spines are best aligned more distally; spines extending close to 3/4 of length of femur; spines of external side stronger and longer than spines of internal side, and also longer than spines in B. rufipennis . Metatibiae weakly curved at midlength. Tarsomeres moderately flattened dorsally.

Abdomen: first three visible abdominal tergites with posterior basal transverse carina well developed; adjacent area a little depressed and with sparse, wide-superficial punctures combined with fine punctures moderately dense; visible tergite 4 with punctures as on tergites 1–3; visible tergites 5–6 only with fine punctures. Visible sternites 1–4 with punctures as on tergites 1–3, but wide-superficial punctures slightly denser; sternites 5–6 only with fine punctures. Male pregenital sternite with deep, narrow U-shaped emargination at posterior margin, as deep as nearly 1/5 of length of sternite (Fig. 17–o). Male genital sternite short (1.94 times longer than wide), moderately asymmetrical, anterior portion occupying 39% and posterior portion 61% of its length, apical emargination deep ( Fig. 19g ). Abdominal styli large.

Aedeagus: length 1.9 mm; oval shape; apex of median lobe narrow and rounded, median lobe parallel sided and narrow, compared to rest of aedeagus which is wider; apical half of aedeagus becoming narrow to base of median lobe, basal half of aedeagus with sides almost homogeneous in width; internal sac visible in anterior half ( Fig. 23d ).

Variability. Total body length in males 11.9 mm (range 10.7–12.7 mm), in females 13.0 (range 12.6–13.5); ratio length/width of head in males 0.75 (range 0.67–0.86), in females 0.87 (range 0.86–0.88); ratio mandibular length/cephalic length in males 1.35 (range 0.96–1.67), in females 1.0 (without variation); ratio cephalic width/pronotal width in males 1.18 (range 1.08–1.26), in females 1.05 (range 1.03–1.06); ratio length/width of pronotum in males 1.12 (range 1.10–1.16), in females 1.2 (range 1.18–1.22); ratio anterior width/posterior width of pronotum in males 1.12 (range 1.07–1.15), in females 1.08 (range 1.07–1.10). Dorsal rows of punctures on pronotum vary from 7:7, 6:6 to 6:7; anterior half of prosternum may be reddish-brown; in small males, spines of posterior femora may be better aligned and, those at its base smaller than they are in large specimens; fifth visible abdominal segment may be black in posterior half and reddish in anterior half, or reddish until anterior 1/4.

Taxonomic comments. Belonuchus mixtecus has a body coloration similar to B. pollens and B. rufipennis , and it is distinguished from both species by the dorsal rows of pronotum formed by six or seven punctures, the more robust body, the male pregenital sternite deeply emarginate at posterior margin and aedeagus large and oval. While in B. pollens and B. rufipennis there are five punctures in each dorsal row of pronotum, the body is less robust, male pregenital sternite is slightly to moderately emarginate at posterior margin, and their aedeagus is smaller and elongate. Belonuchus mixtecus can also be confused with B. erichsoni , and their differences have been indicated in the taxonomic comments of this species.

Etymology. The name of this species refers to the geographical place where it was collected, which is called the “Mixteca Alta” region of Oaxaca.

Type material ( five males, two females): Holotype (male, CC-UAEH): “ México: Oaxaca, San Mateo Peñasco , en jardín, 1788 m, N17°09’7”, W97°3’38”, en nopal podrido, 6-VIII-2001, S. Bautista, J. Asiain y J. Márquez ”.

Paratypes: same data as holotype (5, MAAS). Mexico : Oaxaca: “ San Juan Chicomesuchitl , Rio Grande, 1436 m, N17°18’729”, W96°30’600”, en nopal y mandarina podrida, 16-XI-1999, J. Márquez col.” (1, 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 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 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).