Onthophagus insularis Boheman, 1858

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 : 578-580

Onthophagus insularis Boheman, 1858

( Figures 4 (g – i), 4(o – r), 5(b))

Onthophagus insularis Boheman, 1858: 47

Onthophagus insularis Boheman : Harold 1869: 1031

Diagnosis

This species is very similar to O. confusus but can be distinguished in having the posterolateral margins of the pronotum not flattened superiorly and the foretibiae of male lack the internoapical tooth (distinct and acuminated in O. confusus ).

Redescription

Small-sized species, body length 5 – 6 mm. Colour. Body reddish brown with sides of pronotum reddish, apex and base of elytra with reddish to paler spots, pronotum with faint green or cupreous sheen. Middle-, metafemurs, first and last sternites yellowish to alutaceous, medial sternites brownish with yellowish spots. Tarsi, mouthparts, scape and antennal articles I – V reddish brown, antennal club yellow. Head. Clypeus sub-trapezoidal, largely truncated anteriorly, genal margin slightly but clearly expanded beyond the clypeus. Fronto-clypeal region without carina, vertex of male with two short and parallel horns, head surface finely microsculptured and densely punctated, punctures shallow. Thorax. Anteromedial pronotal protuberance very weak and low (located near the anterior pronotal margin), pronotum with lateral margins very feebly curved to almost straight near anterior angles. Pronotal surface finely microreticulated, punctation simple and very fine, punctures evenly distributed. Elytral surface distinctly microreticulated, opaque to very weakly shining, elytral striae very weakly impressed, interstriae flat to feebly convex, interstrial punctures obsolete, interstria VII with short and straight setae, intervals VI with a single row of setae. Propleuron without tubercles in proximity of the anterior angles of pronotum, propleural carina thin. Metasternum almost flattened, without keel between mesocoxae, with a very thin sulcus at middle, metasternal surface finely and evenly punctated. Abdomen. Pygidium weakly convex, surface yellowish and alutaceous, finely and entirely microreticulated, punctation very small and shallow, lateral punctures associated to short and straight setae. Legs. Foretibiae with four external teeth, internoapical margin of protibiae without a distinct and acuminated tooth. Middle and hind legs unmodified. Male genitalia. In dorsal view, distal-superior area of the paramerites widely curved, external margin slightly curved. In lateral view, distal-inferior area sinuate, with apex distinctly curved downward. Lamella copulatrix with superior right margin swollen, superior left lobe narrow and elongated, apical margin curved, external margin of the superior left lobe deeply excavated. Inferior right lobe longer than inferior left lobe. Secondary lamella wide and sub-trapezoidal, superior margin evenly concave, inferior margin convex, lateral margins straight and convergent towards the superior side ( Figure 4 (o – r)).

Female with clypeus sub-trapezoidal, genal margin slightly expanded beyond the clypeus, fronto-clypeal carina transverse and weakly curved forward, frontal carina sub-trapezoidal (from above) and feebly depressed at middle. Anteromedial pronotal protuberance very weak, pronotal punctures slightly stronger than male, elytra finely microreticulated, with paler to reddish spots at the base and apex (like in male), foretibiae of female larger than male.

Distribution

Doubtful; to date known only from one supposedly Ecuadorian locality (see Remarks below).

Remarks

To our knowledge, O. insularis is today known only on the type specimens (one male and two females), which are deposited at the Naturhistoriska Riksmuseet of Stockholm. This species was collected during the voyage of the Swedish frigate Eugenie around the globe (1851 – 1853) . Although the aim of the expedition was primarily to maintain Swedish commercial connections, the Royal Swedish Academy of Science sent some naturalists on board the Eugenie to collect natural history specimens throughout their travels, and among them Johan Gustaf Hjalmar Kinberg (1820 – 1908) was the recruited zoologist ( Persson 1970) . In 1851, the expedition left from the port of Karlskrona (SE Sweden) and firstly reached the Portuguese Island of Madeira, from where the Eugenie headed straight to Brazil . From Rio de Janeiro, the Eugenie started the circumnavigation of South America, stopping at Montevideo ( Uruguay) and Buenos Aires ( Argentina), then through the Strait of Magellan to arrive at the Pacific side of the continent . On March 1852 they arrived in Valparaiso ( Chile), then farther north in Peru (Callao and San Lorenzo Island) and Ecuador (Port of Guayaquil and Puna Island ) . After a short staying in Guayaquil, the crew headed to the Pearl Islands ( Panama), and then straight to the Galapagos Islands . On 29 July 1852, the frigate arrived in San Francisco (California) and remained there until August to get some repairs and provisions . On September 1852, after visiting Hawaii, the Eugenie reached Tahiti, where they stayed for just a few hours before heading to Sydney , which was the only stop made in Australia .

Once back in Sweden, Carl Henrik Boheman (1796 – 1868), then-curator of the Riksmuseet, was the entomologist in charge to study the specimens collected during the voyage of the Eugenie. From that material, in 1858 he described the new O. insularis , allegedly from Tahiti. However, according to the recent catalogue of insects of that Pacific island ( Paulian 1998), no scarabaeinae dung beetles occur in Tahiti. Furthermore, since 1858, this species name was only mentioned in Harold ’ s (1869) catalogue and never included in any other study. So, this led us to investigate in more depth the real identity of O. insularis .

At first sight, the external morphology of O. insularis led us to believe in a possible Australian Onthophagus related to the species of the posticus group (see Monteith and Storey 2013). However, the examination of the genital organs of the only male belonging to the syntypic series of O. insularis and the comparison with the genital structures of some of the Australian Onthophagus assigned to the posticus group (e.g. O. incornutus and O. kiambram ) allowed us to exclude any direct phyletic relationship between O. insularis and Australian species. Instead, the shape of the parameres and endophallic pieces revealed immediately that O. insularis is actually an American species belonging to the osculatii complex of the hircus group. Importantly, the external morphology and the shape of the superior left lobe of the lamella copulatrix ( Figure 4 ) suggest a close relationship between O. insularis and O. confusus .

The question about the type locality of O. insularis appears to be yet rather uncertain. Nevertheless, considering the above information on the Swedish expedition of the Eugenie and the geographic distribution of closely related species (especially O. confusus ), we can only hypothesize that O. insularis has been collected around Guayaquil, Ecuador. Indeed, the genus Onthophagus is absent in Chile ( González-Chang et al. 2015) and the occurrence of O. insularis in arid and xeric areas like those around Callao ( Peru) seems to be quite doubtful.

Throughout our research, we analysed specimens of O. confusus collected around Guayaquil (e.g. Bosque Protector Cerro Blanco, Ecuador) and it was very interesting to find individuals that exhibited nearly the same pattern of colours as observed in O. insularis (see Figure 4 (a)). Nevertheless, the external morphology (e.g. the presence of a distinct apical tooth on the foretibiae) and importantly the shape of the male genital pieces unquestionably excluded the possibility to identify these specimens as O. insularis . So, at the moment we believe Guayaquil to be the most probable type locality of O. insularis ( Figure 5 (b)).

In order to maintain the nomenclatural stability we designate a male syntype as lectotype of O. insularis (ICZN 1999, Art. 74). The remaining two females belonging to the syntypic series have been properly labelled as paralectotypes. Label data are provided below.

Type specimens examined

Lectotype here designated (♂ NHRS): 1: Taiti. (printed on white label). 2: Kinb. (printed in italics on white label). 3: Type. (printed on white label). 4: insularis Bhn (handwritten in italics on white label). 5: Typus (printed on red label with black border). 6: 5807, E92 + (printed on blue label). 7 : Syntype, Identified by F. Vaz-de-Mello, 2014 (printed on red label). 8: NHRS-JLKB000025273 (printed on white label). 9: LECTOTYPE, Onthophagus insularis Boe., Des. M. Rossini, 2016 (printed and handwritten on red label with black border). Paralectotypes (♀ NHRS): 1: Taiti. (printed on white label) . 2: Kinb. (printed in italics on white label). 3: 5808, E92 + (printed on blue label). 4: Syntype, Identified by F. Vaz-de-Mello, 2014 (printed on red label). 5: NHRS-JLKB000025274 (printed on white label). 6: PARALECTOTYPE, Onthophagus insularis Boe., Des. M. Rossini, 2016 (printed and handwritten on yellow label with black border). (♀ NHRS): 1: Taiti. (printed on white label). 2: Kinb. (printed in italics on white label). 3: 5809, E92 + (printed on blue label). 4: insularis Boh. (handwritten in italics on white label). 5: Syntype, Identified by F. Vaz-de- Mello, 2014 (printed on red label). 6: NHRS-JLKB000025275 (printed on white label). 7: PARALECTOTYPE, Onthophagus insularis Boe., Des. M. Rossini, 2016 (printed and handwritten on yellow label with black border).

Figures

Figure 4. Onthophagus confusus stat. nov. (a, b) Dorsal habitus of male and female. (c, d) Dorsal habitus of the lectotype and original labels (scale bar: 1 mm). (j, k) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (l, m) Lamella copulatrix and accessory lamellae. (n) Female genitalia (scale bar: 0.02 mm). Onthophagus nabeleki. (e, f) Dorsal habitus of the lectotype and original labels (scale bar: 1 mm). Onthophagus insularis. (g–i) Dorsal habitus of the lectotype and paralectotype, original labels of the name-bearing type (scale bar: 1 mm). (o, p) Lateral and dorsal view of the parameres (scale bar: 0.05 mm). (q, r) Lamella copulatrix and accessory lamellae (scale bar: 0.02 mm).

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