Onthophagus nyctopus Bates, 1886

Rossini, Michele, Vaz-de-Mello, Fernando Z. & Zunino, Mario, 2018, A taxonomic revision of the New World Onthophagus Latreille, 1802 (Coleoptera: Scarabaeidae: Scarabaeinae) of the osculatii species-complex, with description of two new species from South America, Journal of Natural History 52 (9 - 10), pp. 541-586 : 569-571

Onthophagus nyctopus Bates, 1886

( Figures 3 (a – d), 3(i – m), 5(b))

Onthophagus nyctopus Bates 1886: 68

Onthophagus nyctopus Bates : Boucomont and Gillet 1927: 207; Boucomont 1932: 305; Blackwelder 1944: 211; Howden and Young 1981: 103; Solís 1987: 97; Gill 1991: 215; Zunino and Halffter 1997: 161; Escobar 2000: 209; Kohlmann and Solís 2001: 225; Medina et al. 2001: 140; Ratcliffe 2002: 17; Zunino 2003: 71; Aguilar-Amuchastegui and Henebry 2007: 65; Kohlmann et al. 2007: 33; Noriega et al. 2007: 83; Pulido- Herrera and Zunino 2007: 111; Pulido-Herrera et al. 2007: 307; González-Maya and Mata-Lorenzen 2008: 460; Delgado and Curoe 2014: 66

Diagnosis

Within the osculatii complex, O. nyctopus can be recognized by the following combination of characters, which are in part shared with O. steinheili : body completely black with strong green iridescence on the anterior half of the pronotum, posteromedial region of pronotum distinctly sericeous with silver iridescence (same exoskeletal texture observed on the body of O. steinheili ). The male has a fronto-clypeal carina (shared only with O. steinheili ), the superior metasternal keel is very weak and swollen (strong and keel-like in O. steinheili ). The female exhibits the same pattern of colour observed in male, frontal carina of female sub-trapezoidal, either depressed or curved backward at middle.

Redescription

Medium to small-sized species, 4 – 6 mm in length. Colour. Body completely black to dark brown, head with reddish and metallic green casts, pronotum with a strong metallic green to cupreous sheen, posteromedial region distinctly sericeous and opaque, with silver iridescence, elytra silky to sericeous, with faint greenish iridescence, pygidium black to reddish brown. Ventral side of the body, femurs, mouthparts, scape and antennal articles I – V reddish-brown, antennal club tan-brown. Head. Margins evenly curved, clypeus barely truncated and reflexed at middle, clypeal and genal margins continuous. Male with a fronto-clypeal carina slightly curved forward, frons with two straight to very weakly curved and convergent horns, head surface with fine and sparse punctation. Thorax. Anteromedial pronotal protuberance of male narrowly and obtusely triangular between the cephalic horns, anterior side always curved, protuberance flanked by two wide depressions, superior side of protuberance convex to weakly depressed at middle, central region of pronotum longitudinally and shallowly sulcate. Pronotal punctation very shallow and evenly distributed, discal punctures larger, with a small central pit (visible at high magnitude, 40× – 50×), posteromedial region with shallower and obsolete punctures. Elytral striae distinct but always shallow, discal interstriae flat, lateral interstriae (VI – VII) slightly more convex and shining. Elytral punctures scattered and shallow, sometimes very obsolete, elytra completely bare (even on the lateral interstriae). Propleuron with an acuminated tooth in proximity of the anterior angles of pronotum, propleural carina distinct and sinuate near external margin. Superior side of the metasternum either simply swollen between mesocoxae or with a very obtuse keel. Abdomen. Pygidium shining and completely bordered, pygidial surface with shallow and evenly distributed punctures. Legs. Foretibiae of male slender, internoapical margin with an obtuse to curved tooth, tip of the apical spur obtuse and slightly curved downward. Middle and hind legs unmodified. Male genitalia. In dorsal view, distal-superior area of the paramerites with apical margin obtuse, lateral margin straight to slightly curved. In lateral view, distal-inferior area sinuate, tips of the paramerites slightly curved downward ( Figure 3 (i), 3(j)). Superior margin of the lamella copulatrix curved on the left side, straight to feebly excavated on the right side. Superior left lobe narrow and sinuate, with apical part curved outward, apex acuminated, external margin widely excavated. Inferior right lobe obliquely developed, slightly longer than the inferior left lobe, basolateral carina of the inferior left lobe present but hardly visible ( Figure 3 (k)). Secondary lamella rounded, left margin widely curved, right margin indistinct, superior margin rather straight ( Figure 3 (k)). Female genitalia. Ventral sclerotization of the vagina distinct, with central and inferior margin more sclerotized, deeply and abruptly excavated at middle ( Figure 3 (m)).

Female differs from male in having two cephalic carinae, fronto-clypeal carina straight to very feebly curved forward, frontal carina sub-trapezoidal, central part slightly bilobed and depressed at middle ( Figure 3 (b)). Anteromedial pronotal protuberance very weak and curved, pronotal and elytral punctation stronger and denser. Minor male is very similar to female, but can be distinguished by the frontal carina often more elevated at both sides, foretibiae slender and last abdominal sternite narrower at middle.

Distribution

From northern Costa Rica (Guanacaste) to central and western Colombia (Valle del Cauca).

Remarks

In this study, we add a new Colombian locality to the distribution of O. nyctopus , extending the distributional range of this species farther South (central region of Valle del Cauca; see ‘ Additional material examined ’). Noriega et al. (2007) reported O. nyctopus from the biogeographical province of Sierra Nevada de Santa Marta, in north-eastern Colombia. We could not confirm the identity of those specimens, but it seems to be completely plausible that O. nyctopus also colonized the northern regions of Colombia.

Howden and Young (1981) were the first authors to mention O. nyctopus from Mexico. Subsequently, even Zunino (2003) and Pulido-Herrera and Zunino (2007) reported this species from the same country. However, none of these authors provided exact localities of collection. On studying the genus Onthophagus in Costa Rica, Kohlmann and Solís (2001) considered O. nyctopus to be a Central American species ( Costa Rica and Panama), suggesting the possible occurrence of this species also in the southern territories of Nicaragua. Nonetheless, they did not elaborate upon the Mexican records reported by Howden and Young (1981).

Throughout our extensive research we found only one specimen, apparently collected in northern Mexico (Sonora) in 1914 . If this locality is correct then a big distributional gap of O. nyctopus is still waiting to be filled in with further data from more intensive sampling in these regions. However, since the lack of sound geographical data to support the Mexican distribution of O. nyctopus , we prefer to maintain our Mexican locality as a doubtful point ( Figure 5 (b)). Therefore, northern Costa Rica (Guanacaste) is considered here to be the northernmost boundary of the geographic distribution of this species .

Type specimen examined

Lectotype designated by Kohlmann and Solís (2001: 225) (♂ BMNH): 1: Syntype (printed on rounded label, white with light-blue border). 2: Type (printed on rounded label, white with red border). 3: V. De Chiriqui, 25 – 4000 ft ., Champion. (printed on white label) . 4: B.C.A., 68. 6. (printed and handwritten on brown label). 5: Onthoph. nyctopus, Bates , ♂ (handwritten in italic on white label). 6: LECTOTYPUS, Onthophagus nyctopus, Bates , por Kohlmann & Solís (printed on red label). Paralectotype (♀ BMNH): 1: Syntype (printed on rounded label, white with light-blue border). 2: Paratype (printed on rounded label, white with red border). 3: V. De Chiriqui, 25 – 4000 ft, Champion. (printed on white label) . 4: B.C.A., 68. 6. (printed and handwritten on brown label). 5: Onthophag. nyctopus, Bates , ♀ (handwritten in italic on white label). 6: PARALECTOTYPUS, Onthophagus nyctopus, Bates , por Kohlmann & Solís (printed on yellow label).

Additional material examined

COLOMBIA: Valle del Cauca: Alto Anchicaya . 500 m. 29-31-VII-1983 (1 ♀ BGc). COSTA RICA: Alajuela: San Ramon . Rio San Lorencito . 800 m . X-XI-1986 (1 ♂, 1 ♀ CMNC). Cartago: Turrialba. 650 m . 28-II-1980 (16 ♂♂, 12 ♀♀ CMNC). Guanacaste: Maritza Biological Station . 550 m . 22-V-1993 (7 ♂♂, 11 ♀♀ CMNC). Heredia: La Selva . Near Puerto Viejo. 50 m . 19-II-1980 (1 ♂, 1 ♀ CMNC). La Selva. 80 m . 19-V-1993 (6 ♂♂, 11 ♀♀ CMNC) Puerto Viejo. Finca La Selva . VI-1979 (5 ♂♂, 2 ♀♀ MCZ) . Puntarenas: Coto Brus. Estación Biologica Las Cruces. 08°47 ’ N, 82°57 ’ W. 1000-1100 m. III-IV-2002 (1 ♂, 2 ♀♀ CEMT) . San Vito. Las Cruces. 1200 m. II-III-1983 (37 ♂♂, 26 ♀♀ CMNC; 2 ♂♂, 2 ♀♀ BGc) . MEXICO: Sonora: Rio Mayo . VII-1914 (1 ♂ CMNC) . PANAMA: Colón: Gatun Lake . Pipeline road. 01-20-VIII-1982 (1 ♂ BGc). Darien: Estación Ambiental Cana. Cerro Pirré. 07°45.32 ’ N, 77°41.07 ’ W. 1300-1450 m. 06-07-VI-1996 (1 ♂, 3 ♀♀ CMNC) . Panama: Cerro Campana. 30-VI-1997 (2 ♂♂, 2 ♀♀ FSCA) . Same locality. 3000 m. 01-VIII-1970 (1 ♀ CEMT). Same locality. 2.3 Km W Capira. 10.3 Km N Panamerican Highway. 825 m . 01- 05-VI-1995 (1 ♂, 1 ♀ CMNC). Chepo-Carti road. 400 m. VII-VIII-1982 (1 ♂, 1 ♀ BGc). Chiriquí: 2 Km N Santa Clara . Hartmann ’ s Finca. VI-VII-1981 (1 ♂, 4 ♀♀ CMNC) . 15 Km NW H. Volcan. Hartmann Finca. 1200 m. 20-31-V-1977 (2 ♂♂, 2 ♀♀ CMNC) . No data (1 ♂ NMPC)

Figures

Figure 3. Onthophagus nyctopus. (a, b) Dorsal habitus of male and female. (c, d) Dorsal habitus of the lectotype and original labels (scale bar: 1 mm). (i, j) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (k, l) Lamella copulatrix and accessory lamellae; arrow indicating the basolateral carina of the inferior left lobe of O. nyctopus. (m) Female genitalia (scale bar: 0.02 mm). Onthophagus steinheili. (e, f) Dorsal habitus of male and female. (g, h) Dorsal habitus of the lectotype and original labels (scale bar: 1 mm). (n, o) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (p, q) Lamella copulatrix and accessory lamellae. (r) Female genitalia (scale bar: 0.02 mm).

Figure 5. Geographic distribution of the species of the osculatii complex.