Oplognathus MacLeay, 1819

Carvalho, Tamara G., Seidel, Matthias & Grossi, Paschoal C., 2021, Taxonomic revision of the genus Oplognathus MacLeay, 1819 (Coleoptera: Scarabaeidae: Rutelinae: Rutelini), European Journal of Taxonomy 764 (1), pp. 62-84 : 64-67

Genus Oplognathus MacLeay, 1819

Oplognathus MacLeay, 1819: 159 ( Fig. 1a–g ).

Oplognathus – Latreille 1829: 553 (catalogue). — Laporte 1840: 124 (catalogue). — Machatschke 1970: 157 (synonymy observation); 1972: 5 (catalogue). — Ratcliffe & Jameson 1989: 135 (general characterization). — Jameson 1990: 415 (phylogeny). — Krajcik 2007: 90 (catalogue). — Grossi & Vaz-de-Mello2015: 221 (collecting report).— Carvalho& Grossi2018:369 (general characterization).

Hoplognathus – Burmeister 1844: 428 (re-description). — Lacordaire 1856: 365 (catalogue). — Ohaus 1905: 322 (species description); 1912: 650 (species description); 1914a: 301 (species description); 1915: 257 (general characterization); 1918: 11 (catalogue); 1934: 41 (re-description). — Blackwelder 1944: 235 (catalogue).

Type species

Oplognathus kirbii MacLeay, 1819 , by monotypy.

Diagnosis

Males with quadrangular, trilobate clypeus ( Fig. 3a–d ), rounded in females ( Fig. 1b, e, g ); clypeus extending beyond labrum in ventral view in both sexes; mandibles with three teeth in incisive area ( Fig. 4a, e, i ); maxillae with six teeth ( Fig. 4b, f, j ); antennae with 10 antennomeres ( Fig. 3a–d ); elytra with 10 striae ( Fig. 1a–g ); mesoventral process present ( Fig. 8a–f ); parameres asymmetrical ( Figs 5–7 ), each paramere with two apical lobes, and one lateral projection.

Redescription

Male

SIZE. Total length: 17.4–22.4 mm; width across prothorax: 8.0– 11.4 mm.

COLOUR. General aspect light yellow varying from yellowish to reddish metallic green, with golden and green reflexes; ventral surface metallic green; pronotum sometimes with black maculae; elytral margins metallic green or copper ( Fig. 1a, c–d, f ).

HEAD ( Fig. 3 ). Reddish brown and/or metallic green. Clypeus subquadrate, surface rugose, setose, apex trilobate, apical and lateral margins elevated; clypeus produced beyond labrum in ventral view. Frontoclypeal suture usually distinct, straight or sinuous. Frons predominantly rectangular, surface glabrous, distinctly punctate, punctures dense; ocular canthus intruding a third of the eye’s length, with scattered yellow setae. Labrum transverse, widely bilobed, setose, never visible from above. Mandibles laminar, rounded, intimately joined to labrum, with three incisive teeth ( Fig. 4a, e, i ). Maxillae setose, galea with six teeth, palpi 4-segmented, last palpomere longer than other three combined, varying from cylindrical to fusiform ( Fig. 4b–c, f–g, j, l ). Mentum sinuous, bilobed or notched, ventral surface setose; labial palpus inserted dorsally on mentum, 3-segmented; last palpomere enlarged ( Fig. 4d, h, m ). Antenna with 10 antennomeres, antennal club 1.3 to 1.8× longer than antennomeres 2–7 combined.

THORAX. Pronotum convex, transverse, about 1.8 times wider than longer, beaded; pronotal bead incomplete posteriorly at middle; surface varying from sparse to densely punctate; punctures small to moderate; maculae varying from two distinct anterolateral spots to two complete elongated maculae; some specimens with spots and maculae obsolete or absent. Each elytron with 10 distinctly punctate striae, punctures fine to moderate, interstriae almost smooth, punctures visible from 10× of magnification; humeri rounded, smooth; elytral apex straight. Hind wings full developed with a group of setae at AA 1+2, setae long and fine, longer than width of first axillar sclerite; AP 3+4 softly setose at base, with fine and minute setae; R 3+4 sclerotized, disc with a distinct row of short setae. Mesoventral process acute, elongated, but never extended beyond anterior procoxal base ( Fig. 8 ). Metafemur with anterior and posterior margins rounded, distinctly developed that other femora, with at least twice the mesofemoral width. Protibia tridentate, teeth reducing in size from apex to base, proximal tooth sometimes obsolete; inner apex with one tiny spur; ventral surface distinctly dilated, convex. Mesotibia with surface rugose, and two oblique carinae: proximal carina with 2–7 spinules, and distal carina with 4–9 spinules, distal carina longer; mesotibial apex truncate with 7–13 spinules and two spurs, inner spur slightly longer. Metatibia wider than mesotibia, with inner margin distinctly rounded, apical spinules varying from 14–22; spurs distinctly short, and flattened, apex less acute than spinules; proximal carina with 2–8 spinules and distal carina with 6–11 spinules. Protarsomere V thickened; inner claw stronger with a basal obtuse tooth. Meso- and metatarsomere ornamented with lateral setae, and inner apical spinules. Meso- and metatarsal claws curved, simple, unequal in thickness; unguitractor plate present with two apical setae.

ABDOMEN. Pygidium flat to weakly convex, subtrapezoidal, transverse, surface rugose and setose; longer setae often on posterior sides. Ventrites metallic green, slightly convex, surface weakly punctate, punctures sparse, with scattered setae, sternites V and VI about twice as long as sternite IV. Parameres asymmetrical, each paramere with 1–2 distal lobes, left lateral expanded with a long projection, apical bifurcation wide, V-shaped ( Figs 5–7 ).

Female ( Fig. 1b, e, g )

Similar to male, differing in the following aspects:

SIZE. Total length: 17.2–22.1 mm; width across prothorax: 7.5–11.1 mm.

HEAD. Apex rounded, never with projections; antennal club distinctly smaller.

THORAX. Pronotum more densely punctate. Elytra more convex, with dilated external margins, and elytral epipleuron wider in ventral view; legs thinner, anterior claws subequal, simple, not dilated.

ABDOMEN. Sternum and pygidium more convex.

Distribution

Brazil. Bahia: Condeúba; Espírito Santo: Palmital; Minas Gerais: Águas Vermelhas, Berizal, Manhumirim, Grão Mogol, Leme do Prado; Paraná: Curitiba; Rio de Janeiro: Rio de Janeiro; São Paulo: São Paulo (Fig. 9).

Nomenclatural history

Oplognathus was described by MacLeay (1819) without ‘H’ at the beginning of the name, but later Burmeister (1844) redescribed the genus as “ Hoplognathus ”, justifying that it would be the correct spelling for the name. Lacordaire (1856) also pointed the “error” of MacLeay, and uses Hoplognathus as a valid name, indicating “ Aplognathus ” as original wrong spelling, but not specifying the cause of the error. Since then, the name Hoplognathus has been widely used, including the description of the new species, generating more synonyms, such as Hoplognathus bahianus and Hoplognathus helmenreichi . Only Machatschke (1970) comments that Hoplognathus is a synonym, but when using Oplognathus , the spelling appears as “ Oplongnathus ”. Already in his catalogue, Machatschke (1972) cites “ Oplognathus ” using the original spelling, which proves to be a typing error in the previous publications. Ratcliffe & Jameson (1989) note this fact and show the correct use “ Oplognathus MacLeay (not Hoplognathus as in Burmeister 1844; Ohaus 1918, 1934; Blackwelder 1944)”, because according to Article 23 (ICZN 1999), the Principle of Priority, the oldest name should be used. In the original description, MacLeay (1819) does not detail the etymology of Oplognathus , but the Hoplo prefix, from the Greek Hoplon, means ‘any tool or implement of armour and shield’ while Gnathus, from the Greek, means ‘mandible, mouth’, possibly due to the distinct shape of the clypeus of the males. Perhaps, this explains the insistence of later authors ( Burmeister 1844; Lacordaire 1856) to use the spelling Hoplognathus , instead of Oplognathus , as correct. However, as there is no written indication of this, and the addition of ‘H’ is not a clear, obvious and necessary correction of the name, Oplognathus must be maintained, following the original description and not its subsequent spelling (ICZN 1999, Art. 33).

Although Burmeister corrected the name of the genus, this does not mean that Ohaus intended to describe Oplognathus bahianus and Oplognathus helmenreichi in a genus other than Oplognathus . Thus, the author’s name is written here without brackets, since the species is basically in its original combination.

Oplognathus kirbii was cited by Laporte (1840) as Oplognathus kirbyi and since then, both spellings were widely used, in addition to Hoplognathus kirbii and Hoplognathus kirbyi , it is common to find four spellings for this species throughout the literature. There are no details for replacing ‘i’ with ‘y’, but we can suppose Laporte (1840) to make this change on the assumption that MacLeay intended to honour the naturalist William Kirby. ICZN (1999, Article 58.2) states that the use of ‘i’ and ‘y’ are ‘variant spellings’ deemed to be identical. However, as MacLeay (1819) makes the description with no detail about etymology, it is prudent to keep the original spelling Oplognathus kirbii and not to use the subsequent spellings (ICZN 1999, Art. 33).

Oplognathus helmenreichi was described for the first time based on a single specimen in the collection of W.J.C. Weber by Ohaus (1905) with this spelling (for the specific epithet) and the locality Buenos Aires, Argentina. Later, Ohaus wrote that he found ( Ohaus 1914a: 22) several specimens of this species in the Museum of Vienna, but he described them as a variety “ var. maculicollis ”. These specimens were labelled “Helmr.”, realizing that the name of the collector was Helmreichen and not Helmenreich, as published in Ohaus (1905). Although Ohaus (1914a) has described the variety as “ Hoplognathus helmreicheni var. maculicollis ” in the original publication, the correct name is Hoplognathus helmenreichi var. maculicollis (as written on the original label). In this case, Ohaus (1914a) made an unjustified emendation almost 10 years after the original publication of the species, not being recognized by the Code to validate a name (ICZN 1999, Art. 19.1, 33.2). Still, the latter spelling is used as valid, violating the Principle of Priority (ICZN 1999, Art. 23.9).

Key to adult species of Oplognathus MacLeay, 1819

1. Males with weakly trilobed clypeus, sides usually parallel; last maxillary palpomere cylindrical; mentum longer than wider, anterior margin sinuous; mesoventral process long (exceeding the anterior margin on mesocoxae, never exceeding the procoxae); (if female, clypeus rounded) ....... 2

– Males with strongly trilobed clypeus, sides clearly divergent ( Fig. 3b ); last maxillary palpomere fusiform ( Fig. 4g ); mentum as long as wide, anterior margin notched ( Fig. 4h ); mesoventral process short (not exceeding the anterior margin on mesocoxae), slightly flat ( Fig. 8b, e ); (if female, the clypeus rounded, and last maxillary palpomere cylindrical). Brazil: Bahia, Minas Gerais ............... .................................................................................................................... O. bahianus Ohaus, 1912

2. Body distinctly bicoloured. Pronotum dark green with yellow maculae. Elytra reddish brown to orange yellow; size varying from 17.2 mm to 18.6 mm in length ( Fig. 1c–e ); anterior margin of mentum slightly sinuous ( Fig. 4m ); females without dilated epipleuron, simple. Brazil: Minas Gerais, Paraná ...................................................................................... O. helmenreichi Ohaus, 1905

– Body colour uniformly yellowish golden, sometimes with spots or maculae on pronotum. Elytra golden yellow, with greenish reflections; size varying from 19.15 mm to 22.0 mm in length ( Fig. 1a– b ); females with distinctly dilated epipleuron. Brazil: Espírito Santo; Minas Gerais; Paraná; Rio de Janeiro; São Paulo ........................................................................................ O. kirbii MacLeay, 1819

Figures

Fig. 1. a–b. Oplognathus kirbii MacLeay, 1819. a. Neotype, ♂ (NHMUK). b. Female specimen (MZUSP). c. O. helmenreichi Ohaus, 1905, holotype, ♂ (ZMHB). d–e. O. helmenreichi var.maculicollis Ohaus, 1914. d. Syntype, ♂ (ZMHB). e. Syntype, ♀ (ZMHB). f–g. O. bahianus Ohaus, 1912. f. Syntype, ♂ (ZMHB). g. Female specimen (EPGC). Scale bar = 5 mm.

Fig. 3. Head and pronotum details. a. Oplognathus kirbii MacLeay, 1819, male specimen (ZMHB). b. O. bahianus Ohaus, 1912, syntype, ♂ (ZMHB). c. O. helmenreichiOhaus, 1905, holotype, ♂ (ZMHB). d. O. helmenreichi var. maculicollis Ohaus, 1914, syntype, ♂ (ZMHB). Scale bar = 1 mm.

Fig. 4. Mouthparts. a–d. Oplognathus kirbii MacLeay, 1819 (ZMHB). e–h. O. bahianus Ohaus, 1912 (ZMHB). i–m. O. helmenreichi Ohaus, 1905 (ZMHB). a, e, i. Right mandible. b, f, j. Right maxilla. c, g, l. Detail of the last maxillary palpomere. d, h, m. Mentum. Scale bar = 1 mm.

Fig. 8. Patterns of mesoventral process. a, d. Oplognathus kirbii MacLeay, 1819 (MZUSP). b, e. O. bahianus Ohaus, 1912 (ZMHB). c, f. O. helmenreichi Ohaus, 1905 (CERPE). Scale bar = 1 mm.

Fig. 5. Aedeagus in dorsal (a, e) y lateral view (b–c, d, f). a–c. Oplognathus kirbii MacLeay, 1819 (ZMHB). d–f. Oplognathus bahianus Ohaus, 1912, syntype, ♂ (ZMHB). Scale bar = 1 mm.

Fig. 6. Aedeagus in dorsal (a, e) and lateral view (b–c, d–f). a–c. Oplognathus helmenreichi Ohaus, 1905, holotype, ♂ (ZMHB). d–f. O. helmenreichi var. maculicollis Ohaus, 1914, syntype, ♂ (ZMHB). Scale bar = 1 mm.

Fig. 7. Variation in male genitalia. a–d. Oplognathus kirbii MacLeay, 1819 (a-b: CEMT; c-d: ZMHB). e–h. O. helmenreichi Ohaus, 1905 (ZMHB). i–m. O. bahianus Ohaus, 1912 (CERPE). Scale bar = 1 mm.