Belonuchus zunilensis ( Sharp, 1885 )

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 49-51

Belonuchus zunilensis ( Sharp, 1885)

Figs. 4d, 13c, 17n, 19c, 22i, 26b

Philonthus zunilensis Sharp, 1885: 418 . Belonuchus zunilensis comb. nov. ex Philonthus ( Navarrete-Heredia et al. 2002) .

Total body length 11.1 mm. Black on head, antennae, pronotum, prosternum, almost entire fifth visible abdominal segment (except anterior border), sixth visible segment and abdominal styli. Reddish on elytra, scutellum, legs, mesoventrite, metaventrite, 1–4 visible abdominal segments and anterior border of fifth segment. Mandibles, maxillary and labial palpi reddish-brown.

Head: subquadrate; slightly transverse (ratio 0.81). Dorsal surface with moderate microsculpture like wavy lines; sulcate longitudinal midline visible in anterior half of head reaching level of eyes; front weakly foveate between antennal insertions and slightly posteriad. Eyes slightly more than 0.5 times the cephalic lateral length, somewhat protruding laterally. First antennomere slightly longer than 2–3 combined, 4–6 elongate, 7 as long as wide, 8–10 transverse. Mandibles 1.11 times longer than head; each with two small, well separated teeth (basal and middle); base of mandibles with conspicuous microsculpture like wavy lines; mandibular channel with external margin not carinate and internal margin carinate at base, extending like impressed line slightly forward of level of middle tooth. Apical palpomere of maxillary palpi 1.3 times longer than preapical palpomere. Apical palpomere of labial palpi 1.4 times longer than preapical palpomere. Head 1.11 times wider than pronotum. Ventral surface with fine, very sparse punctures.

Thorax: pronotum with left dorsal row formed by five punctures and right dorsal row by six punctures; fore- most puncture in each row looks somewhat separated from anterior margin (at least by one puncture diameter); ratio length/width of pronotum 1.17; as wide at anterior corners than as posterior corners. Scutellum with punctures sparse; elytra with punctures moderately dense. Prosternum elevated near anterior margin, but without constriction separating this area from remaining surface. Intercoxal process of mesoventrite shield-shaped; transverse discal ridge not very distinct, broadly U-shaped, reaching close to margin of intercoxal process, but not touching it. Profemur with external row of spines as widely separated from base as from apex, formed by eight to nine spines slightly increasing in size toward apex, but smaller than spines of anterior tibiae; internal margin with four to five apical small spines. Metatrochanter with apex straight and pointed, not forming a hook, as long as 1/4 of length of metafemur, which is clearly curved at internal margin for about 1/2 of its length ( Fig. 13c). Metatibia straight. Tarsomeres slender and flattened dorsally.

Abdomen: visible tergites 1–3 with posterior basal transverse carina not completely straight, faintly visible on tergite 3; adjacent area almost flat on tergite 1 and slightly depressed on tergites 2–3; entire surface of tergite 1 with sparse, wide-superficial punctures combined with fine punctures; tergites 2–4 with wide-superficial punctures combined with fine punctures in anterior half, posterior half only with sparse, fine punctures; tergites 5–6 only with sparse, fine punctures. Sternites with pattern of punctures as on tergites. Male pregenital sternite with posterior margin slightly carinate, acute at center and straight at sides (Fig. 17n). Male genital sternite very long (3.33 times longer than wide), slightly symmetrical, anterior portion occupying 50% and posterior portion 50% of its length; apical emargination deep ( Fig. 19c). Abdominal styli slender at apex.

Aedeagus: length 1.5 mm; elongate shape, with apex moderately acute; apical half moderately narrower than basal half; internal sac visible, very characteristic ( Fig. 22i).

Variability. Only one other female specimen of the type series is available, which has a total length of 13.1 mm (bigger than male); ratio length/width of head 0.82; mandibular length/cephalic length 1.07; cephalic width/pronotal width 1.06; length/width of pronotum 1.19; anterior width/posterior width of pronotum 1.0. The number of punctures in each dorsal row of pronotum is six (also the first one is somewhat separated from anterior margin).

Taxonomic comments. We first believe it is necessary to explain why we have included B. zunilensis in the trochanterinus group and not B. aenigmaticus , since the males of both species have a metatrochanter acute apically. We studied only one male specimen of B. zunilensis , the lectotype. We assume that the small spine of the metatrochanter of this specimen, not forming a hook, corresponds to a small size specimen, and we suppose that in large specimens the metatrochanter can be a hook, as has been noticed in other species of this group, as B. apiciventris . Also, the metafemur is clearly curved at the internal margin for about 1/2 of its length, this suggests the possibility that the metatrochanter can be a hook in this species because this curvature in the metafemur may be a modification for not hindering the hook or to accommodate the hook, as we observed in several species of this group. However, these asseverations can be tested until more male specimens of this species can be studied. For now, we decided to place this species as part of the trochanterinus group.

On the other hand, we analyzed 10 male specimens of B. aenigmaticus . In all males, the apex of the metatrochanter ends in a small spine and the metafemur is not curved. We suppose the variability in body size of males of B. aenigmaticus is represented by the 10 studied specimens ( 8.1–9.6 mm), as well as the poor or not variability of the metatrochanter and metafemur. So, we think it is less possible that this species can be part of the trochanterinus group, but it is necessary to study more specimens, and also it is the reason for the name of this species

Belonuchus zunilensis has previously been recorded for Mexico (Santiago Jiménez 1999; Navarrete-Heredia et al. 2002; Asiain et al. 2011; Márquez & Asiain 2017) due to great similarity with B. linuzensis . However, only the study of the aedeagus and genital segment of the type material of B. zunilensis allowed us to recognize that these are two species and that, for now, B. zunilensis should not be registered from Mexico. Still, we assume that something similar to B. trochanterinus may occur, and that the occurrence of B. zunilensis in Chiapas and Oaxaca is possible. The fundamental differences to distinguish both species have been indicated in taxonomic comments of B. linuzensis . Lectotype of this species is designated here taking into account Article 74.7 of the ICZN and its recommendations, in order to establish more clearly the identity of this species.

Type material examined ( one male, one female): Lectotype (male, NHM): “ Philonthus zunilensis Type D.S. Cerro Zunil 4-5000 ft / Type/ B.C.A.Col. I.2 Philonthus zunilensis, Sharp / Cerro Zunil, Guatemala. Champion / Sharp Coll. 1905-313/ Lectotype Philonthus zunilensis Sharp, 1885 , Márquez & Asiain des. 2022” . Paralectotype: “ Philonthus zunilensis D.S. Cerro Zunil , Guatemala, 4-5000 ft. Champion (on the plaque with the lectotype)/ Cerro Zunil Guatemala, Champion / B.C.A.Col. I.2 Philonthus zunilensis, Sharp / Sharp Coll. 1905-313” (f 1, NHM) .

Group 2: rufipennis

Included species: B. bidens Sharp, 1885 , B. erichsoni Bernhauer, 1917 , B. jalappensis Bernhauer, 1917 , B. mixtecus sp. nov., B. pollens Sharp, 1885 , and B. rufipennis ( Fabricius, 1801) .

Diagnosis of the rufipennis group: head without temporal carina; male mandibles not expanded at base ( Fig. 10e); mandibular length very variable; number of punctures in each dorsal row of pronotum variable; elytra reddish, abdomen bicolored (reddish and black); both sexes with unmodified posterior trochanters; males with two rows of spines on the inside of the posterior femora (except B. jalappensis that has spines in both sexes, although they are small) ( Figs. 13d–f); tarsomeres somewhat flattened dorsally; aedeagus with reduced paramere ( Figs. 23a–f).

Key to Mexican species of Belonuchus of the rufipennis group

1 Pronotum reddish; first two or three visible abdominal segments reddish and remaining segments black ( Fig. 4h); male pregenital sternite not emarginate at posterior margin ( Fig. 15d); male genital sternite moderately elongate (2.86 times longer than wide), very asymmetrical ( Fig. 19f); aedeagus as in Fig. 23c......................................... B . jalappensis

- Pronotum black ( e.g., Fig. 4f); at least first four visible abdominal segments reddish or black; pregenital and genital sternite of males, and aedeagus different as above.................................................................... 2

2(1) Head of males with a pair of projections in shape of a small horn on frontal margin, one “horn” at side of each antenna ( Fig. 10e); first four visible abdominal segments and anterior half of fifth black ( Fig. 4f); aedeagus as in Fig. 23a....... B . bidens

- Head of males without frontal projections; at least first four visible abdominal segments reddish; aedeagus different as above ................................................................................................... 3

3(2) Pronotum with six or seven punctures in each dorsal row ( Figs. 4g, 5a); male pregenital sternite deeply emarginate at posterior margin (Figs. 17m, o); male genital sternite short (2.29 times longer than wide) ( Figs. 19e, g); aedeagus large (length 1.90–1.95 mm)................................................................................................ 4

- Pronotum with five punctures in each dorsal row (variably also six) ( Figs. 5c, d); male pregenital sternite variably weakly emarginate at posterior margin ( Figs. 15n, 16j); male genital sternite moderately large to very large (2.53–3.19 times longer than wide) ( Figs. 19h, i); aedeagus shorter than in previous option............................................... 5

4(3) Abdomen only with sixth visible segment black (its anterior border reddish) ( Fig. 4g); metafemora of males not flattened in basal half of its external surface; metatibiae of males straight; fourth visible abdominal tergite with posterior basal transverse carina as indistinct line at sides and absent medially; aedeagus as in Fig. 23b............................. B . erichsoni

- Abdomen with major part of fifth visible abdominal segment and entire sixth black ( Fig. 5a); metafemora of males somewhat wide and flattened in basal half of external surface; metatibiae of males weakly curved at middle portion of its length ( Fig. 13e); fourth visible abdominal tergite without posterior basal transverse carina; aedeagus as in Fig. 23d............. B . mixtecus

5(3) Anterior and middle coxae reddish; prosternum and mesoventrite reddish; first antennomere, and sometimes apical antennomere, lighter than rest of antennomeres; male pregenital sternite with broad U-shaped emargination at posterior margin ( Fig. 16j); male genital sternite very elongate (3.19 times longer than wide) ( Fig. 19i); aedeagus as in Fig. 23f....... B . rufipennis

- Anterior and middle coxae black; prosternum and mesoventrite black; first and apical antennomeres black or almost black; male pregenital sternite weakly emarginate at posterior margin ( Fig. 15n); male genital sternite moderately elongate (2.53 times longer than wide) ( Fig. 19h); aedeagus as in Fig. 23e.................................................. B . pollens