Frolov, A. V. & Akhmetova, L. A. 2015. A new brachypterous scarab species, Orphnus longicornis (Coleoptera: Scarabaeidae: Orphninae), from the East African Rift. Zootaxa, 4039(3): 475–477
A new brachypterous scarab species, Orphnus longicornis (Coleoptera: Scarabaeidae: Orphninae), from the East African Rift
Laboratory of Insect Systematics, Zoological Institute, Russian Academy of Sciences, Universitetskaya nab., 1, St.-Petersburg, 199034 Russia. Email: email@example.com
Universidade Federal de Mato Grosso, Instituto de Biociências, Departamento de Biologia e Zoologia, Av. Fernando Corrêa da Costa, 2367, Boa Esperança, 78060-900 Cuiabá, MT, Brazil.
The Afrotropical Region is the center of the diversity of the scarab beetle genus Orphnus MacLeay, 1819 (Coleoptera: Scarabaeidae: Orphninae), with 94 species occurring from Sahel in the north to Little Karoo in the south (Paulian, 1948; Petrovitz, 1971; Frolov, 2008). The East African Rift is one of the richest regions of the Afrotropics housing more than 20 species of Orphnus (Paulian, 1948; Frolov, 2013), most of which are endemic to this region. Yet the scarab beetle fauna of the East African Rift, and especially the Eastern Arc Mountains, is still inadequately studied. Examination of the material housed in the Museum of Natural History of Humboldt-Universität, Berlin, Germany (ZMHUB), revealed a series of brachypterous Orphnus beetles belonging to an undescribed species. The new species is described and illustrated below.
Photographs were taken with a Leica MZ9.5 stereo microscope and a Leica DFC290 digital camera from dry specimens except for internal sac sclerites, which were photographed in glycerol. Partially focused serial images were combined in Helicon Focus software (Helicon Soft Ltd.) to produce completely focused images. Locality map was prepared with ArcGIS software (ESRI Inc.).
Orphnus (Orphnus) longicornis Frolov & Akhmetova, new species
Type material. Holotype, male with the label "D. Ost-Africa Iringa [Tanzania, Iringa]" (ZMHUB). Paratypes, males: 6 specimens with the same data as the holotype; 5 specimens with the label “Mittel Uhehe [Tanzania, Iringa region], 1500-1700 m, 30.XI.12”; 1 specimen with the label “D.O.Africa Oldoway [Tanzania, Oldoway Gorge]” (ZMHUB).
Description. Holotype, male. Body elongate, convex, shiny (Fig. 1); length 10.5 mm, width 6.1 mm. Color uniformly black. Head: Clypeus wide, with convex anterior margin, rounded laterally, finely bordered. Genae small, not protruding past eyes. Frontal suture feebly distinct laterally, broadly interrupted in the middle. Clypeus with long, slender horn, curved apically in lateral view (Fig. 2); the horn is at least 1/3 longer than in other described Orphnus species. Dorsal surface of head almost impunctate. Labrum deeply sinuate in the middle, feebly protruding past clypeus. Pronotum: with rounded sides, about 1.2 times wider than long, with impressed and slightly concave disc and large tubercle in the middle near base. Anterior angles acute; posterior angles rounded, indistinct in dorsal view. Pronotum bordered on anterior margin and base. Base of pronotum rugose. Sides with coarse, rounded punctures separated by about 0.5–1.0 puncture diameters. Lateral margins with long, sparse, brown setae. Scutellum: shape subtriangular, narrowly rounded apically, about 1/20 the length of elytra. Elytra: convex, about as wide as long, widest in the middle, with almost indistinct humeral umbones. Striae indistinct. Elytra with coarse, ocellate punctation; punctures sparser on disc. Wings: reduced, about 1/3 length of elytra. Legs: Protibiae with 3 outer teeth. Lateral margin basad of outer teeth not crenulate. Apical spur of protibia absent. Protarsi of the holotype broken. Mesolegs and metalegs similar in shape; metafemora and metatibiae about 1/8 longer than the mesofemora and mesotibiae. Tibiae somewhat triangular with 2 apical spurs, inner margin almost straight, with 1 transverse keel. Upper spur of tibiae as long as two basal tarsomeres. Claws 1/3 length of apical tarsomere. Femora almost impunctate. Abdomen: Abdominal sternites irregularly punctate, pubescent, with sparse, long setae. Visible sternite 6 medially about 2 times longer than sternites 2–5 combined. Pygidium: Surface irregularly punctate with transverse punctures. Aedeagus: with long, curved downwards parameres tapering apically (Fig. 6).
Variability. The paratypes are smaller than the holotype, with the body length from 9.2–6.0 mm; most specimens are around 7.0 mm long. Body color varies from almost black to dark brown; the specimen from Oldoway has the pronotum and head darker than the elytra (Fig. 5) — the coloration rarely encountered in the Orphninae, which are normally uniformly colored. Most of the examined specimens have more or less distinct bronze and greenish metallic tint of the upper side of the body (especially apparent on the pronotum, Figs. 4–5). In the Orphninae, distinct metallic tint of the dry specimens is rarely found. It is prominent in the similar species O. luminosus Benderitter and in Stenosternus costatus Karsch from São Tomé island (Frolov & Akhmetova, 2015). Head and pronotum armature vary reasonably within the type series. Clypeal horn varies from long, slightly shorter than that of the holotype in the larger specimen to rather short yet distinct in the smallest specimen (Figs. 3–5). Shape of the pronotum varies from slightly excavated disc and pulled, tubercle-shaped base (similar to the holotype); to almost flat, slightly excavated disc and a tubercle basad of the disc (not protruding past pronotum base in dorsal view); to almost convex dorsal side with a shallow depression posteriorly and without a tubercle.
Diagnosis. Males of O. longicornis with well-developed head and pronotum armature can be easily separated by the shape of this armature: a very long, slender clypeal horn (almost 1.5 longer than head width) and a protruding, tubercle-shaped basal margin of pronotum. Males of O. longicornis with less developed armature are similar to the males of O. luminosus Benderitter in habitus, punctation, and slight metallic tint of the body but they can be separated from the latter by the shape of the parameres which are longer, more curved downward, and more acute apically (compare with Fig. 5 in Frolov, 2008).
Distribution. The new species is known from two rather distant districts (Fig. 7). The specimens with the label "D. Ost-Africa Iringa" might have been collected near the town of Iringa, Tanzania. The specimens with the label “Mittel Uhehe” might have also been collected not far from Iringa. According to Redmayne (1968), “Uhehe” is the upland area between Great Ruaha and Little Ruaha rivers, southwest of Iringa. Both localities lie within Uzungwa, the largest block of the Eastern Arc Afromontane forest. One specimen was found in Oldoway Gorge, some 500 km north of Iringa. Although Oldoway Gorge is not a part of the Eastern Arc Mountains, it lies within the Ngorongoro escarpment mostly covered by the East African montane forests.
Etymology. From Latin longus, long, and cornu, horn, referring to the long clypeal horn in males.
We are thankful to Johannes Frisch and Joachim Willers (ZMHUB) for the loan of the material. This work was partly supported by the Russian state research project 01201351189 and Russian Foundation for Basic Research (grant 13-04-01002-a).
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