Pachycerus opimus, (GYLLENHAL, 1834)

Meregalli, Massimo, 2009, Revision of the Indo-African Pachycerus Schoenherr, 1823, with a description of four new species (Coleoptera: Curculionidae: Lixinae), Zoological Journal of the Linnean Society 157 (2), pp. 295-325 : 298-302

PACHYCERUS OPIMUS ( GYLLENHAL, 1834)

Cleonus opimus Gyllenhal, 1834: 185 .

Pachycerus opimus (Gyllenhal) : Chevrolat, 1873: 110. Pachycerus opimus: Faust, 1904: 223 .

Cleonus (Pachycerus) opimus: Csiki, 1934: 53 .

Cleonus (Pachycerus) opimus: Alfieri, 1976: 255 .

Type specimen: not found.

Neotype female (designated here): 1. Blank orange label; 2. naevulus Buq, Cat Dj 3, p 282 (light blue, hw); 3. Typus (red, pr); 4. Coll. Chevrolat (pr); 5. Cleonus opimus Gyll. 1834 , Neotypus, 2007 Meregalli des. (red, pr) ( NHRS, coll. Schoenherr, drawer # 186) .

Other specimens: Senegal: ‘ Senegal, Baden’ 1 ♀ ; ‘ Senegal, Dämel’ 1 ♀ (coll. Faust, SMTD); ‘ Senegal’ 1 ♀ ( BMNH); ‘ Pachycerus senegalensis Dej Buq / Seneg. / 34888/185/ = 138 Faust’, 1 ♂ ( ZMHB) ; ‘ Mauritania ‘ Sénégal, Rosso à Boutilimit, 8.X.47, Miré’, 1 ♀ ( MNHN, coll. de Peyerimhoff) ; Marocco: ‘ Rio de Oro, Ouad Zammel [22°14′N, 15°45′W], IV. Mateu’, 1 ♀ ( MNHN, coll. de Peyerimhoff). No data: ‘472/coll. Chevrolat’, 1 ♀ ( NHRS) ; Madagascar (dubious locality): ‘ Madagasc. , Tipitz’, 1 ♂ ( SMTD) .

Type: There are analogies between the description of C. opimus and that given in the same work by Gyllenhal (1834) for C. senegalensis discussed above. In both cases Gyllenhal received the specimens from- Chevrolat, as the sentence ‘ Senegalia . Ex Musaeo Dom Chevrolat, sub hoc nomine ad describendum amice communicatus ’ ( Senegal, from Mr. Chevrolat’s collection, kindly conveyed under this name for description) confirms. It also suggests that only a single specimen (‘ communicatus ’, in singular) was examined. Cleonus opimus was then briefly cited in Schoenherr (1842), probably by Fåhraeus, who compiled the Cleonus section, without adding further data. Although the genus Pachycerus had already been proposed ( Schoenherr, 1823), only Chevrolat (1873) included C. opimus in it. Chevrolat (1873: 110) also referenced a synonym of P. opimus , ‘ Navosus Buqt., var. Linegalensis [sic], Dej., Cat., 3, p. 282’. This (misspelled) reference evidently refers to Dejean (1837: 282), where the names ‘ Pachycerus Naevosus Buquet’ and ‘ P. Senegalensis Dej. ’ were listed. It is surprisingly similar to the label of one of the specimens found in Schoenherr’s collection, originally from Chevrolat, listed under C. senegalensis , which reads ‘ naevulus Buq, Cat Dj 3, p 282’. This suggests that Chevrolat was referring to this specimen when he wrote the synonymic note. The epithet naevosus (or navosus or naevulus) Buquet does not seem to have been validly described, and is not cited by Sherborn (1922–1933). The type specimen of C. opimus could not be found in the collections examined, so a neotype may be designated. Whether a neotype designation for P. opimus fulfils the provisions of article 75, ICZN (1999), in particular the 75.3 ‘qualifying conditions’, should be questioned. Although the identity of P. opimus was never questioned [indeed, it was seldom cited in the literature, and never appeared in any taxonomic paper after Faust (1904)], the sympatry of this species with three other taxa of the genus, the very old description, the absence of any original illustration, and the presence of the sister species P. hippali sp. nov. in Arabia and East Africa suggest that it is advisable to fix the usage of the epithet. The historical specimen originally belonging to Chevrolat’s collection, now conserved at NHRS in Schoenherr’s collection, seems to be a good candidate, and it is therefore designated here as the neotype of C. opimus .

Measurements: Body length excluding rostrum: 13.95 mm. Rostrum: length, 2.83 mm; width, 1.49 mm; ratio, 1.90. Pronotum: length, 3.66 mm; width, 4.48 mm; ratio, 0.82. Elytra: length, 9.57 mm; width, 6.12 mm; ratio, 1.56. Ratio of elytral to pronotal length: 2.61 (neotype).

Redescription: Body oval, integument glossy, black, with simple and bifid whitish scales ( Figs 1, 10 ). Rostrum robust, quadrangular in transverse section, dorsolateral margins keeled, glossy, sparsely punctured, subparallel, barely broadened apicad, median keel convex, broad, smooth, with a single basal puncture beyond head, anteriorly reaching antennal insertion, where a shallow elongated fovea is sometimes present; dorsum weakly depressed in the two furrows delimited by the central and lateral keels; apical plate flattened, depressed, with a slightly raised median line; epistoma weakly prominent at middle; surface in the large furrows rough, with very dense irregular puncturation; in lateral view rostrum nearly straight up to antennal insertion, then strongly curved to apex, thickened from base to mid-length, underside convex; upper margins of scrobes curved, weakly sinuate basad, extended towards lower margin of eyes, but separated from the eyes by a short scaly space; lower margin of scrobes shortly curved downwards, reaching underside of rostrum near its base; scrobes very deep, slightly broadened basad. Vestiture composed of oval-lanceolate whitish or whiteyellowish scales, nearly centripetal, and densely covering integument on dorsal furrows and less dense, forwards or outwards directed on apical plate; scales bifid, but with very short teeth on dorsal furrows, and simple and narrower towards apex, on apex, transformed into slightly erect setae; on sides narrow, sparse on triangular plate beyond eyes, and more dense, mixed with some white setae on pregenae ( Figs 5, 6 ). Antennae short, scaly, scape shorter than funicle, moderately curved forwards, and thickened from base; segment I of funicle conical, twice as long as wide, segment II as long as wide, segments III–VII progressively broadened and transverse; club very slender, finely hairy, segment I with barely apparent basal glossy scales, segments II and III together longer than segment I, apex long and acuminate ( Fig. 16 ). Head transverse, densely and roughly punctured, with two tubercles above eyes; vertex finely keeled at centre, in correspondence with the base of the median keel of rostrum; base of head with a distinct transversal keel, slightly curved forwards; eyes large, elongate, slightly convex, and broadened on upper half. Pronotum large, convex, base obliquely prominent towards elytra, broadly curved at centre towards scutellum, sides subrectilinear, weakly convergent, maximum width near base, shortly convergent at apex; apex curved, prominent over head; postocular lobes weakly distinct; dorsum with a barely raised, very narrow median keel, higher near apex, sometimes finely channelled, particularly at mid-length, and slightly broadened in a glossy granule on disc; dorsum of pronotum in its median part with an approximately triangular convex area, broadened from apex to base, deeply and densely punctured, margins of the punctures glossy, irregularly convex, forming small granules and short keels; dorsolateral part of pronotum, by sides of the median convexity, flattened–depressed, broadened anteriorly, with smooth, rough integument, sparsely granulose; sides weakly compressed, particularly forwards, with some large, glossy isolate granules. Vestiture composed of whitish oval scales, bifid in apical half, relatively dense in the anterior dorsolateral depressions, and extended near to base with a few patches; very scarce on median convexity, and often present along the median keel ( Fig. 2 ). Scutellum: small and triangular. Elytra oval, at base as wide as thorax base, widened at humeri, with maximum width near base, sides nearly parallel, slightly compressed beyond humeri, more strongly converging after midlength, broadly rounded at apex; in lateral view nearly completely flattened from base to apex, declivity not curved downwards, indistinct; intervals broader than striae, very slightly convex, irregularly sculptured, with punctures as well as transverse wrinkles, and sparse, small glossy granules, usually larger towards base and apex, and relatively prominent, sharper along lateral intervals, lateral margin, and near apex; base with raised broad and sculptured irregular humps at beginning of intervals 2–3 and 4–5; striae narrower than intervals, scarcely delimited, with irregular, barely differentiated shallow, round or elongate punctures, often fused in narrow furrows. Vestiture composed of whitish scales of variable size, with a few as long as wide, bifid up to near base, and with the majority longer, glossy white, connate up to mid-length ( Fig. 13 ), disposed in relatively dense patches, not hiding integument, and absent on two large bare patches near mid-length, where only small, round spots of scales are sometimes present. Legs slender, scaly, with usually single, in part bifid, acuminate glossy scales, and with moderately erect setae, more dense on tibiae; femora very scarcely broadened at middle, fore tibiae narrow, rectilinear, scarcely broadened at apex, with an apical fringe of strong denticles; middle and hind tibiae shorter and straight; tarsi slender, all segments with glossy white simple scales and setae, segment I triangular, as long as wide, segment II subcylindrical, slightly wider than long, segment III with small lobes; onychium nearly as long as the first three segments of tarsi, claws weakly widened, connate up to the middle. Underside of tarsi with a highly reduced adhesive pad, limited to the median part of segment III, and with some spiny setae on sides. Ventrites convex, segments I and II of the same length, segments III and IV half as long as segment II, segment V transverse, weakly impressed near apex on female, flat on male. Vestiture dense, with bifid or trifurcate elliptical scales, with very narrow teeth, particularly the central one, with four small bare spots on segment I, six spots on segment II, and two lateral spots on segments III and IV, bare spots not always clearly delimited ( Fig. 8 ). Sternite VIII of female subquadrate, with apodeme nearly as long as plate; arms strong, gently divergent, curvilinear, moderately widened, window of plate not sclerotized on basal and median parts; sclerotization of apex of plate broad, uniform between apex of arms; margin with dense short setae ( Fig. 15 ). Spermatheca slender, curved, cornu thick, not acuminate, curved at 90° with respect to nodulus, which is straight and thickened ( Fig. 24 ); hemisternites broadened up to apex, not angularly constricted; styli cylindrical and slender ( Fig. 18 ). Aedeagus tubular, slender, with median lobe scarcely curved, apical lamella gently tapering, and subtruncate at apex ( Figs 22, 25, 28 ).

Variation: The range of variation is relatively conspicuous. The body length ranges between 10.69 and 13.95 mm, and the length: width of the elytra is always greater than 1.50; the sculpture is always relatively dense and deep, but in some specimens the granules are higher and more frequent, and more distinct among the scales; the anterior part of the pronotum always has the typical dorsolateral broad impressions, which usually have some granules inside, visible among the scales; the median keel can be more or less complete from base to apex, although it is always scarcely distinct near the base, and higher in the anterior half; the integument can be strongly and deeply wrinkled and/or punctured, extremely irregular, or more shallowly sculptured. The bifid elytral scales can be round, with short teeth, or have slender teeth, connate at basal third. The female genitalia are relatively variable: the spermatheca is sometimes more slender, and its nodulus is less thickened; however, its apex is never acute in the specimens examined; the sternite VIII can have arms that are sublinearly broadened or more distinctly curved.

Affinities: The differences between P. opimus and the sister species P. hippali sp. nov. are discussed in the description of the latter species (also see Figs 1–28 ). Pachycerus opimus and P. hippali sp. nov. are very easily differentiated from all of the other species of the genus because of the very typical shape and sculpture of the pronotum ( Figs 2, 4 ). In addition, P. sahelicus sp. nov. and P. badeni are smaller, and do not have bifid scales on the dorsum; the eyes, in lateral view, reach the upper margin of the head. These last traits should also allow the differentiation of P. efflatouni . Pachycerus vestitus has very long setae on the elytra. The northernmost population of P. opimus is nearly sympatric with P. simonae sp. nov., which differs in the vestiture composed of slender scales, connate at their base, and with long, narrow teeth, the longer rostrum, the vertex not raised above the eyes, the pronotum with isolate granules, and the sternite VIII of the female with fully sclerotized lamina.

Distribution ( Fig. 108 ): Pachycerus opimus is found in the south-western Sahara and the western Sahel. The specimen from Wadi Aideb, a tributary of Wadi Kansisrob ( Egypt, Gebel Elba) cited by Alfieri (1976) belongs to the sister species, P. hippali sp. nov., which is diffused along the coasts of the Red Sea. The indication of Madagascar is doubtful: considering the broad gap between Madagascar and the range of the other specimens examined, the absence of any recent finding of this species from the island, and the extreme morphological similarity of this specimen with those from Senegal, including the shape of the aedeagus, a labelling error has very likely occurred.

Figures

Figure 108. The Indo-African species of Pachycerus. Distribution map. Map taken from Encarta World Atlas 2000 (Microsoft Corporation), refined with Photoshop 7.0.

Figures 1–12. Pachycerus opimus (Gyllenhal, 1834), neotype female: body (1, 10); rostrum (5, 6); pronotum (2); ventrites (8). Pachycerus hippali sp. nov., holotypus: body (3, 11); rostrum (7, 9); pronotum (4); ventrites (12). Scale bars: 1, 3, 10, 11, 5 mm; 2, 4, 8, 12, 2 mm; 5–7, 9, 1 mm.

Figures 13–28. Pachycerus opimus (Gyllenhal, 1834), neotype female: antenna (16); detail of elytral scales (13); sternite VIII (15). Pachycerus opimus, Senegal, female: hemisternites (18); spermatheca (24). Pachycerus opimus, Senegal, male: aedeagus, dorsum, profile and lamella (22, 25, 28). Pachycerus hippali sp. nov., holotypus: antenna (17); detail of elytral scales (14); aedeagus, dorsum, profile and lamella (21, 26, 27). Pachycerus hippali sp. nov., Kordofan, paratypus female: sternite VIII (20); hemisternites (19); spermatheca (23). Scale bars: 15–17, 20–22, 25, 26, 1 mm; 18, 19, 0.5 mm; 23, 24, 27, 28, 0.2 mm.