Onthophagus montishannoniae, Krikken & Huijbregts, 2008

Krikken, J. & Huijbregts, J., 2008, Two new taxa from the Lesser Sundas in the genus Onthophagus (Coleoptera: Scarabaeidae: Scarabaeinae), Journal of Natural History 42 (43 - 44), pp. 2735-2746 : 2737-2740

Onthophagus montishannoniae n. sp.

( Figures 1–8 , 21 )

Description

Holotype (male). Length ca 8.2 mm. Colour blackish-brown, very shiny, forebody black, remainder medium to dark brown (also dependent on available lighting). Dorsal side glabrous; pilosity conspicuously sparse on ventral side and legs, brownish.

Clypeus blackish; margin slightly reflexed, apex widely rounded, slightly truncate, abruptly reflexed; clypeogenal border virtually continuous, gena distinctly angular; head surface generally abundantly, finely, superficially punctate, clypeus anteriorly somewhat rugulate, with distinct transverse plica behind apex; clypeofrontal ridge absent; clypeofrons slightly matt, more so on genae (due to microreticulation, at X60); paraocular horns long, slightly reclined and convergent, very feebly helicoidal, transverse on cross-section, apex blunted; not interconnected at base. Eyes rather large, elliptic, with ca 15 facet rows across widest point; genal canthus incomplete, by far not reaching occipital side, eyes jutting out laterally (in full-face view); ratio (in dorsal view) interocular distance/single (transverse) full eye width ca 3.3.

Pronotum blackish, shiny, with moderately convex general surface, anterior declivity steeper, feebly deplanate; disc without midline impression; anterior section of lateral border (full-face) almost straight, very slightly concave; anterolateral angle ca 85 °, shortly rounded; posterior section of lateral border virtually straight, posterolateral angle very obtuse; lateral border distinctly marginate, base widely rounded, very finely but distinctly marginate (particularly opposite interstriae 1–4); pronotal punctation abundant, scattered, fine, punctures separated by three to five punctural diameters; secondary punctation vague (X60); punctation on anterior declivity sparser and finer; estimated density of primary punctation on disc 40–55/ 0.25 mm 2, diameters ca 0.03 mm and less.

Elytra brown, moderately shiny, striae well-defined, with distinct punctures, in stria 1 separated by one to two diameters, slightly crenulating interstriae, more so laterad, with interpunctural distance increasing; interstriae almost flat, with abundant, very fine, scattered punctures, on very vaguely shagreened background.

Antennae slender, scapus sharply ridged in front, segment 4 longer than 3; 5 and 6 very short; colour yellowish. Metasternum anteriorly unmodified, surface simply slightly convex; posteriorly with slight midline impression, disc at most with abundant, fine punctures, anteromedian lobe in front with some seta-bearing punctures; lateral wings glabrous, with fine subocellate punctures and with indistinct microreticulation. Abdominal sternites virtually glabrous; anal sternite medially narrowed. Pygidium slightly convex, glabrous; derm with abundant, fine, simple punctures; base marginate; anal margin thickened.

Legs very slender. Protibia with 3+1 larger denticles, and fine proximal serration (9–11 small teeth), serration also distinct between denticles 1–2–3; apico-internal angle with broad tuft-like row of long, yellow-brown setae; terminal spur elongateacuminate, curved. Protarsus very long and slender. Meso- and metatibiae slender, their transversely elliptic apices lined with spines; terminal spurs unmodified, acuminate, tip slightly curved. Femoral undersides sparsely punctate-setose. Meso- and metatarsi long, slender, internal side lined with distally decreasing number of stiff setae. Segment 1 of metatarsus shorter than segments 2–5 combined; approximate length proportions metatibial spur//metatarsal segments 1–5: 25//30/ 10/7/5/11.

Parameres ( Figures 21A and B ). Measurements in mm. Maximum width of head 2.5. Median length of pronotum 2.5, maximum width 4.1. Sutural length of elytra 3.4, maximum width combined 4.4.

Variation and sexual dimorphism

Length 6.0– 8.5 mm. In minor males frontovertexal horns reduced to short tubercles; in females they are absent ( Figure 3 ), being replaced by solid plate posteriorly limited by widely arcuate crest. Other differences as follows: clypeal apex of females slightly sinuate-emarginate, very slightly reflexed; clypeal plica absent, surface densely rugulate-punctate; pronotum evenly convex; protibial tuft consisting of some scattered setae only. Microsculpture on head of both sexes variable.

Distance between genal tips of female (in Figure 3 ) ca 2.2 mm.

Diagnostic remarks

O. montishannoniae is recognizable from the following combination of characters. Head (male) without transverse ridges, apart from being slightly transversely swollen medially behind anterior margin (5clypeal plica); pair of complanate paraocular horns present (very short in minor males, absent in females); female with deplanate frontovertexal surface posteriorly limited by ridge, without any horn-like elevations. Clypeal apex widely rounded or truncate (male) to feebly bisinuate (female), lacking projection(s). Genae with virtually rectangular lateral tip, posteriorly by far not reaching occipital side. Eyes (full-face, note posteriorly widely open foramen) relatively wide in relation to interocular distance. Pygidium glabrous, evenly convex, finely, simply, abundantly punctate; base marginate. Protibia (male) with distinctly penicillate apex. Anteromedian declivity of pronotum (male) steep, slightly deplanate, remainder of pronotum evenly convex; pronotum of female entire, slightly, evenly convex. Parameral apex narrowly spatuliform. Blackbrown, elytra usually lighter, very shiny; dorsum virtually completely glabrous (at X40).

Derivation of species name

This species is dedicated to our colleague Arno van Berge Henegouwen, the firstmentioned collector, its name being latinized from his surname.

Material examined

Holotype male ( RMNH) from Indonesia : Flores: between Woloare and Nuabosi, 400m, 14 April 1986, A.L. van Berge Henegouwen and S. Pariwono, #bh149, disturbed monsoon forest, pitfall trap baited with human faeces; 7 male and 15 female paratypes, same label data as holotype. Total 23 males and females, in RMNH, MUDH.

The Onthophagus (Parascatonomus) dux subgroup

Introductory comments

This is a small assemblage within the larger (Parascatonomus) tricornis group, the subgroup including the three species-group taxa treated hereafter (see also Boucomont (1914), his tricornis group 3, Balthasar (1963) and Kon et al. (2000)). There are other subgroups of larger or smaller Parascatonomus with a distinct clypeal tooth, but their members (a) do not have a completely granulate pronotum like those in the dux subgroup, (b) lack the median vertexal tubercle, or (c) lack both. Bali, like Java, has O. accedens accedens , but on the other (eastern) side of the seaway, on Lombok, begins the range of accedens nusatenggaricus, here proposed as a new subspecies – a species-level difference would, in our view, require greater differences, for instance in the male genitalia; additionally, both forms seem to be allopatric. The nominate subspecies appears locally common on Java and Bali, and we have here given new records based on material in Dutch collections. O. dux is known only from Borneo, and seems quite widespread, being variable in colour and size. We have not seen material of the dux subgroup from nearby western regions (like Sumatra, the Malay Peninsula), but would not be surprised if members turned up there as well; a genuine relative may be O. damaki Masumoto, Hanboonsong and Ochi, 2002 , known from a small male (ca 10 mm) collected in north-east Thailand. Beware of the use of older keys ( Boucomont 1914; Balthasar 1963), with couplets indicating black versus cupreous forebodies (see remark on variation under dux ). Pictures are helpful in the identification; the diagnostic characters are all illustrated in this paper.

Subgroup diagnosis

Vertex (between eyes) with low median (subconiform, more or less elongate) protrusion. Clypeus with short anteromedian tooth (with rounded apex; not a Y- or T-shaped projection). Clypeofrontal transition at most with obsolescent transverse ridge between clypeogenal sutures. Intercoxal lobe of metasternum very protuberant in front, prowshaped (subgeneric character). Entire pronotum smoothly granulate, granules large, more or less elongate (any anterior impression may be differently sculptured). Antennal club modified, segment 1 enlarged, more or less cup-shaped, 2 and 3 relatively normal; scapus relatively short, non-serrate. Anterior side of pronotum (major males) with wide, shallow impression or with moderate protuberance. Base of pronotum medially slightly produced caudad (subangular). Black (or brown), virtually uniform, forebody may be metallic (cupreous). Protibia with short, acuminate apico-internal protrusion, with four external denticles and short proximal serration. Sexual dimorphism slight, mainly apparent in the (median) width of the anal sternite. Length usually 10–16 mm.

Range and ecology

South-east Asia, including Lesser Sundas. In (semi)natural forest, found in association with dung and/or carrion.

Figures

Figures 1–8. Onthophagus montishannoniae. (1–2, 4–8) Male holotype; (3) female paratype. (1) habitus, oblique; (2) head, full-face, male; (3) female; (4) male, horns, axial view; (5) pronotum, dorsal; (6) elytron, dorsal; (7) protibia and tarsus, upperside; (8) metatibia, underside.

Figures 21–24. Aedeagus of Onthophagus species. (A) Upper side; (B) lateral; (21) O. montishannoniae, holotype; (22) accedens nusatenggaricus, holotype; (23) accedens accedens, Bali; (24) dux, Sabah.