Belonuchus aenigmaticus, Márquez & Asiain, 2022

Márquez, Juan & Asiain, Julieta, 2022, Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae), Zootaxa 5152 (1), pp. 1-129 : 76-77

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Belonuchus aenigmaticus

sp. nov.

Belonuchus aenigmaticus sp. nov.

Figs. 8a View FIGURE 8 , 13h View FIGURE 13 , 16d View FIGURE 16 , 20d View FIGURE 20 , 24h View FIGURE 24 , 33a View FIGURE 33

Total body length 9.2 mm. Black on head, antennae (except apical antennomere), pronotum, posterior half of prosternum, 3/4 of fifth visible abdominal segment, all sixth and abdominal styli. Reddish on elytra, legs, sterna (except for posterior half of prosternum), visible abdominal segments 1–4 and anterior 1/4 of 5, posterior margin of pregenital sternite, genital segment and base of styli. Mandibles and scutellum brown.

Head: subquadrate, dorsally slightly convex; ratio length/width 0.9. Dorsal surface with sulcate longitudinal midline slightly visible in anterior half of head or slightly further back; front moderately foveate between antennal insertions. Eyes slightly longer than 0.5 times the cephalic lateral length and clearly protruding at sides. Antennomere 1 as long as antennomeres 2–3 combined, antennomere 2 slightly shorter than 3, 4 as long as wide, 5–10 transverse. Mandibles shorter than head (ratio 0.88); each mandible with two well separated teeth (basal and middle), both of small size; mandibular channel slightly developed, with external margin weakly carinate and internal margin well developed like impressed line, extending slightly beyond middle tooth level. Apical palpomere of maxillary and labial palpi slightly more than 1.5 times longer than preapical palpomere. Ventral surface with sparse punctures and fine setae toward posterior corners, in addition to punctures with fine setae on each side. Head 1.12 times wider than pronotum.

Thorax: each dorsal row of pronotum with six punctures; pronotum 1.12 times longer than wide, almost as wide at anterior corners as at posterior corners (ratio 1.04). Scutellum darker and with denser broad punctures than on elytra, latter fine moderately dense punctures. Area near anterior margin slightly impressed and separated from posterior area. Intercoxal process of mesoventrite with shape intermediate between shield and scutellum; transverse discal ridge diffusely impressed, broadly U-shaped or V-shaped, not meeting margin of intercoxal process laterally. Profemur with row of spines only along external margin at middle 2/4 of femur length, basal spines smaller than apical spines, not more than eight to nine spines; internal margin near apex with two or three small spines. Metatrochanter with its apex ending in an inconspicuous spine ( Fig. 13h View FIGURE 13 ). Remainder of legs without modifications. Tarsomeres flattened dorsally.

Abdomen: first three visible tergites with posterior basal transverse carina well developed; adjacent area weakly depressed on tergites 1–2, and less so on tergite 3; depression on tergite 1 with wide-superficial punctures moderately dense in more than its anterior half, in tergites 2–3 this type of punctures covering nearly their anterior half; tergite 4 with sparse wide-superficial punctures and tergites 5–6 only with fine punctures, which are present also on previous tergites. Visible sternites 1–5 with posterior basal transverse carina somewhat separated from anterior margin; with punctation pattern similar to that of tergites, although slightly denser. Male pregenital sternite slightly emarginate at posterior margin ( Fig. 16d View FIGURE 16 ). Male genital sternite short (2.0 times longer than wide), very asymmetrical, anterior portion occupying 28% and posterior portion 72% of its length, apical emargination very deep ( Fig. 20d View FIGURE 20 ). Abdominal styli slender.

Aedeagus: length 1.4 mm; cone shaped; apex moderately acute; apical half narrowing gradually toward apex, basal half ovoid and wider than apical half; internal sac conspicuous ( Fig. 24h View FIGURE 24 ).

Variability. Total body length in males 8.81 mm (range 8.1–9.6 mm), in females 9.4 mm (range 8.7–10.5); ratio length/width of head in males 0.86 (range 0.83–0.88), in females 0.89 (range 0.85–0.96); ratio mandibular length/ cephalic length in males 0.87 (range 0.85–0.92), in females 0.87 (range 0.81–0.92); ratio cephalic width/pronotal width in males 1.13 (range 1.05–1.19), in females 1.09 (range 1.07–1.13); ratio length/width of pronotum in males 1.14 (range 1.11–1.22), in females 1.18 (range 1.12–1.25); ratio anterior width/posterior width of pronotum in males 1.05 (range 1.03–1.09), in females 1.04 (range 1.04–1.05). Furthermore, the apical or apical and sub-apical antennomeres may be reddish; dorsal rows of pronotum with great variability in number of punctures: 5:5, 6:5, 5:6, 6:6, 7:6, 7:7. Scutellum is reddish or brown in most specimens, but in some it may be almost black. Prosternum may have reddish anterior half and black posterior half or entirely reddish. Transverse discal ridge on anterior half of mesoventrite may be better developed in some specimens. The outer row of spines on the profemur can be difficult to distinguish. Metatrochanters of males may have their apex like a very small spine or it may not end in a spine as in females.

Taxonomic comments. This species is very similar to B. optatus in the following terms: overall length, coloration pattern, the few spines at the anterior tibiae in males, the posterior trochanters only spine-shaped at apex, and a similar size and shape of both the genital sternite and aedeagus. Belonuchus aenigmaticus , however, has fewer punctures on the dorsal surface of the head, mainly towards posterior corners, there are five to seven punctures in each dorsal row of the pronotum, which do not extend below three quarters of the pronotal length, the scutellum is reddish (with some variation to dark), the male pregenital sternite is slightly emarginate at the posterior margin, and its aedeagus is slightly larger, with the apex less acute and the internal sac more conspicuous. In B. optatus , there are more punctures on the dorsal surface of the head, and there are seven to nine punctures in each dorsal row of the pronotum that extend very close to posterior margin. In addition, the scutellum is black, the male pregenital sternite is slightly emarginate in posterior margin and the aedeagus is smaller, with a more acute apex and the hardly visible internal sac.

On the other hand, B. aenigmaticus can be confused with B. rufipennis because of its similar body length and coloration pattern. Belonuchus aenigmaticus differs from B. rufipennis in the reddish scutellum, the lack of spines on the male metafemur, row of spines on profemur formed by few small spines, and differences in the genital sternite and aedeagus. In B. rufipennis the scutellum is black or almost black, males have two rows of spines on the posterior femora, with the spines on the external row of anterior femurs being larger and more numerous, and their genital sternite and aedeagus are different.

Additionally, B. aenigmaticus can be confused with B. moquinus Casey, 1884 , from the southern United States of America because both species have a similar body color, and males lack the two aligned rows of spines on the posterior femora ( Smetana 1995). Even the aedeagus is somewhat similar, but the median lobe is different in B. moquinus , with a long, thin and sharp apex in both the ventral and lateral view. Furthermore, the genital sternite is elongate, with apical emargination short and V-shaped, and the scutellum is darker than the elytra. Belonuchus aenigmaticus has a reddish scutellum, almost similar to the color of elytra, the genital sternite is short, with very deep apical sinuation, and the aedeagus is cone-shaped, its apex is moderately acute, with the apical half gradually narrowing toward apex, and the basal half is oval and wider than the apical half.

In the taxonomic comments of B. zunilensis some arguments are included that motivated the inclusion of this species in the platypterus group and not in the trochanterinus group.

Etymology. The name of this species is derived from the word “aenigma” and refers to the fact that its correct placement into the species group platypterus or trochanterinus is an enigma (see taxonomic comments), as well as its great similarity with B. optatus , B. rufipennis and B. moquinus .

Type material (10 males, eight females): Holotype (male, CC-UAEH) : “ México: Hidalgo, La Misión, Las Pilas , N21°7’8.1”, W99°7’26.1”, bosque mesófilo de montaña, trampa de intercepción de vuelo, 12 a 19-VII-2018, J. Márquez y A. Lora cols.” GoogleMaps . Paratypes: Mexico: Hidalgo: “ Chapulhuacán, Puerto del Zopilote , bosque mesófilo de montaña, 1134 m, N21°09.9’ 7.9”, W98°55.8’ 04.0”, NTP-80 (calamar) #4, 28-VIII a 11-IX-2011, J. Márquez col.” (1, CC-UAEH) GoogleMaps . Same data, except: “NTP-80 (calamar) #8” (1, CC-UAEH) . Same data, except: “NTP-80 (calamar) #3” (1, CC-UAEH) . Chapulhuacán , Tamaulipas, bosque mesófilo de montaña, 1134 m, N21° 09.9’ 7.9”, W98°55.8’ 04.0”, NTP-80 (calamar) #1, 12 a 26-III-2011. J. Márquez col.” (1, CC-UAEH) GoogleMaps . Same data, except: “NTP-80 (calamar) #2” (1, CC-UAEH) . Same data, except: “NTP-80 (calamar) #3” (1, CC-UAEH) . “ Jacala de Ledezma, P.N. Los Mármoles, camino a Plomosas , bosque de pino-encino, 1793 m, N20°57’36”, W99°13’2.5”, en hongo, 11-X-2007, J. Márquez, J. Asiain y S. Sierra cols.” (1, CC-UAEH) GoogleMaps . “ Molango, Acuatitlán , bosque mesófilo de montaña, 1715 m, N20°45’38.4”, W88°42’50.7”, NTP-80 (calamar) #8, 15 a 29-IV-2011, J. Márquez col.” (1, CC-UAEH) GoogleMaps . “ Pacula, camino al Membrillar del Fraile, río Moctezuma , N99°23´28”, W21°5´26.8”, 903 m, vegetación riparia, NTP-80 (calamar), 20-I a 25-II-2010, J. Islas col.” (1, CC-UAEH) . “ Tlanchinol, camino a Apantlazol , El Pozo, bosque mesófilo de montaña, 1391 m, N20°59’6.73”, W98°37’ 39.86”, NTP-80 (calamar) #8, 1 a 22-X- 2011, J. Márquez col.” (1, CC-UAEH) GoogleMaps . “ Zimapán, P.N. Los Mármoles, Minas Viejas , bosque de encino, 1892 m, N20°55’5.2”, W99° 12’41.1”, NTP-80 (calamar), del 11-X al 17-XI-2007, J. Márquez, J. Asiain y S. Sierra cols.” (4, CC-UAEH) GoogleMaps . Same data, except: “13-VII al 18-VIII-2007 ” (1, CC-UAEH) . “ Zimapán, P.N. Los Mármoles, Trancas , bosque de encino, 2444m, N20°48’12.2”, W99°14’ 41”, NTP-80 (calamar), 13-X a 17-XI-2007, J. Asiain, S. Sierra y J. Márquez cols.” (1, CC-UAEH) GoogleMaps . Same data, except: “coprotrampa, 22-VI al 12-VII-2007 ” (1, CC-UAEH) .