Pachycerus sahelicus, Meregalli, 2009

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 : 312-316

PACHYCERUS SAHELICUS SP. NOV.

Type locality: Senegal, Bambey , 14°42′N, 16°28′W. Holotype female: Senegal: ‘ Senegal, Bambey, [14°42’N, 16°28’W], 30.VIII.1949, Richard Toll, on rice twigs/ Pres by Com Inst Ent, BM 1955–49’ ( BMNH).

Paratypes: Senegal: same data as the holotype, 2 ♀ (1 BMNH, 1 MER) ; ‘ Senegal / Bowring, 63 47*/7669’, 1 ♂ ( BMNH) . Senegal: ‘ Senegal (light blue label)/ senegalensis, Dj Cat 3, 282 (light blue label)/ Coll. Chevrolat’, 1 ♀ ( NHRS) . Burkina Faso: ‘ Ob. Volta, Pundu , [= Burkina Faso, Pondou, 12°12′N, 3°35′W], Olsufiew’, 1 ♂ ( NHRS) ; ‘Franz. Sudan, oberer Volta, Pundu, ges. Olsufieff’, 2 ♀. (1 NHMB, 1 MER) . Mali: ‘ Mali, Khouna [six different localities named Khouna have been found in maps of Mali], 30.IX.1969, H. Mathes, 1 ♀ ( RMCA) ; N Cameroun, Yagoua , 10°21′N, 15°14′E, 2 ♀ (1 RMCA, 1 MER) ; Sudan ‘ Sudan, Prov. Darfur , El Fasher [= Al Fashir, 13°37′N, 25°21′E], 5.8.1977, H.J. Bremer legit, gekätschert’, 1 ♀ ( CFRE) ; no data: ‘3877’, 1 ♂ ( BMNH) .

Diagnosis: A Pachycerus similar and apparently related to P. badeni and P. efflatouni . It is characterized by the rostrum with keeled margins, a narrow median keel interrupted at the antennal insertion, the transverse pronotum with a subtrapezoidal depression on dorsum, and low humps on the sides, the elytra with whitish simple scales, relatively uniformly distributed, and absent from two central subrectangular patches, and short semi-erect setae; ventrite I with four, and ventrite II with six, bare spots.

Measurements: Body length excluding rostrum: 10.37 mm. Rostrum: length, 2.31 mm; width, 1.26 mm; ratio, 1.83. Pronotum: length, 2.54 mm; width, 3.25 mm; ratio, 0.78. Elytra: length, 6.94 mm; width, 4.45 mm; ratio, 1.56. Ratio of elytral to pronotal length: 2.73 (holotype).

Description ( Figs 71–84 ): Body oval-elliptical, integument black on head, pronotum, and base of elytra, dark reddish on apical half of elytra, underside, legs, and antennae, glossy ( Figs 71–72 ). Rostrum rectilinear, robust, subquadrate in transverse section, dorsolateral margins keeled, straight, glossy, and smooth, subparallel, barely converging forwards; dorsum flat, median line distinct, narrow, moderately raised, higher towards vertex, and progressively flattened towards apical part, interrupted beyond antennal insertion; surface between median and dorsolateral keels roughly sculptured, densely and irregularly punctured, interspaces of punctures much narrower than punctures; epistoma prominent at middle; sides between dorsolateral margins and upper margin of scrobes barely visible from above; in lateral view rostrum weakly curved, dorsolateral margins slightly concave from base to antennal insertion, and convex above antennal insertion; median keel visible, weakly convex; sides in front of eyes triangular, sharply delimited by upper margin of scrobes and dorsolateral keels, glossy and irregularly punctured; upper margin of scrobes straight, obtusely raised, reaching lower margin of eyes; scrobes narrow and rectilinear, deep, lower margin reaching underside or rostrum at its mid-length. Vestiture composed of lanceolate, relatively dense, whitish simple scales, centripetal, and inserted on dorsal part of rostrum, and narrow, slender short setae on sides ( Figs 73–74 ). Antennae short, scape and funicle scaly; scape shorter than funicle, thickened from base, and very moderately curved forwards; funicle nearly as thick as apex of scape, with all segments of equal width; segment I barely longer than wide, segment II weakly transverse, segments III–VII transverse and short; club elliptical, finely hairy, except at base of segment I, scaly and glossy on inner side, segment II as long as segment I, segment III long, and acuminate ( Fig. 80 ). Head small, transverse, vertex flat, interocular pit indistinct, vertex roughly punctured, with a narrow short central keel; eyes large, elongate, vertical, and very slightly convex. Pronotum transverse, base bisinuate, moderately prominent towards scutellum, sides barely widened from base to point of maximum width, slightly beyond mid-length, shortly converging at apex; dorsum with irregular sculpture, forming an irregularly rhomboidal weak impression on disc, limited laterally by glossy, raised and punctured broad obtuse ridges, curved outwards from apex to middle of dorsolateral part, and from here converging towards centre of pronotal base, expanded towards sides, and entirely covered with very dense and irregular punctures; internal part of the rhomboidal figure with some granules at centre, and with a narrow carina from centre to apex; sides with three or four small round glossy granules, isolated, clearly distinct; anterior margin with distinct, regular postocular lobes, and with short postocular setae. Sculpture of sides irregular, with relatively small and shallow punctures. Vestiture composed of lanceolate whitish scales, relatively dense on the central shallow impression, and sparse, not hiding integument on the raised glossy parts, scales generally simple, with a few bifid; sides with distinctly thicker vestiture of scales identical to those of dorsum ( Fig. 76 ). Scutellum small, reddish, glossy, and bare. Elytra elliptical, base curved, as wide as base of pronotum, sides moderately broadened, subparallel, maximum width near humeri, gently converging at apex, individually rounded at apex, with external margin in front of apex of interval 3 with an acute granule; in lateral view flattened, very uniformly and moderately convex, declivity only visible as a small sinuosity after apex of interval 5, not curved downwards; surface densely and minutely wrinkled, particularly on suture and interval 3; intervals flat, all of the same width, excepting interval 3, which is slightly larger, linear, and a little more raised; base of intervals 3 and 5 with a glossy, wrinkled hump; striae broader than intervals, composed of round punctures not well delimited and irregularly aligned. Vestiture composed of whitish lanceolate glossy simple scales ( Fig. 75 ), relatively dense over the whole surface, but absent from two rectangular nearly bare patches in median position from interval 3 to interval 8; setae sparse, regularly aligned, short, and semi-erect. Legs short, scaly, and with hair-like setae obliquely inserted; femora scarcely broadened at middle; tibiae straight, slender, flattened, apex of fore tibiae slightly expanded, with several yellowish short spines; tarsi short, segment I narrow, very small, segment II trapezoidal, as long as wide, segment III with lobes scarcely developed; onychium at least as long as segments I–III of tarsi, claws very robust, connected for half of their length, not divergent, thickened up to near apex; underside with adhesive pad small, limited to segment III of middle and hind tarsi, and also present on segment II of fore tarsi. Ventrites convex, intercoxal process of ventrite I broadly rounded; ventrite II longer than ventrite I at its shortest point; ventrites III and IV very short; ventrite V transverse, three times as wide as long, at middle with some granules, and depressed near apex. Vestiture very dense, composed of elliptical white-greyish, often imbricate scales, bifid from base, with each tooth broad and glossy; ventrite I with four round small bare spots, not well delimited; ventrite II with six spots, larger and more visible ( Fig. 77 ). Sternite VIII with broad plate, sclerotized in its apical part ( Fig. 84 ); spermatheca with thick and curved cornu, not acutely pointed at apex; nodulus tapering basally, moderately thickened ( Fig. 79 ); hemisternites short, broad, styli shortly cylindrical, oblique at apex; symbiont pouches robust, elongate, and thick ( Fig. 81 ).

Description of the male and variation: The male does not differ significantly from the female. Ventrites I and II are flattened at the middle, and ventrite V is a little longer and not depressed before the apex. The aedeagus is similar to that of the other species of the genus: it has a slender, moderately and regularly curved median lobe, and a short, subtriangular apical lamella ( Figs 78, 82–83 ). The specimens examined are rather similar regarding morphology, sculpture, and vestiture; body length, 7.5–10.4 mm. The irregularly rectangular bare patch on the elytra can reach as far as the lateral margin or can be interrupted at interval 8: in some specimens there are one or two small groups of scales and some setae present inside the bare patch; in the specimen from Pundu smaller brownish scales nearly cover the patch completely. The granules on the side of the pronotum are sometimes small and nearly indistinct, or are larger, glossier, and more raised. The specimen from Cameroon does not show any significant morphological difference. Those from Burkina Faso have the median keel of the pronotum extended also behind the central granules, although this part of the keel is smaller and scarcely evident. The specimen from Sudan is the smallest: it has a denser vestiture of scales, which are also slightly larger in size; the granules on the sides of the pronotum and on the ventrites are not distinct.

Affinities: See the preliminary discussion for remarks about the incompatibility between the description of C. senegalensis and the new species.

A further taxonomic question regards its relationships with P. efflatouni (see above for notes on this species). According to the description, the two species seem closely related, so whether the Sahelian specimens should be referred to P. efflatouni may be questioned. The absence of any type material of this specimen, and of specimens from Yemen, renders the interpretation of the African Pachycerus very complex: it apparently differs from the Yemenite taxon by several traits, with particular regard to the absence of large, round bare black patches on the elytra, to which Tewfik gave great importance, both in the text and in the schematic drawings (see Fig. 70 ). The differentiating traits are summarized here, with the states of P. efflatouni reported verbatim in parenthesis. Median keel on head barely distinct beyond the interocular pit (‘median carina... continued in a straight carina reaching the back of the head’); rostrum laterally and ventrally with scales and setae, and lacking any bifid scale (‘rostrum clothed with many bristle-like hairs together with a few scattered yellowish-white bifid scales-like ones directed anteri- orly’); scale on underside of head bifid (‘the scaly hairs on the genae are quinquefid’); segment I of antennal funicle barely longer than wide, and barely longer than segment II (according to the drawing in Tewfik, 1942: 173, fig. 3, segment I longer than wide and distinctly larger, broader, and longer than segment II); disc of pronotum with a distinct rhomboidal impression, and with two glossy raised granules near median line (according to the drawing, the sculpture of the disc of the pronotum has two shallow impressions; no glossy granule was cited for P. efflatouni ), and in lateral view lacking highly raised granules (according to Fig. 2 of the original drawing, pronotum in lateral view with clearly raised granules); pronotum with relatively dense vestiture of whitish scales (‘pronotum... devoid of scaly or any other type of hairs’); scutellum present, clearly visible (‘scutellum indistinct’); base of intervals 3 and 7 distinctly raised, much more elongate, glossy, and devoid of scales {base of elytra differently structured, according to the description and the drawing, ‘anterior margin possesses distinct elevated granules [probably referring to the base of interval 3], and ‘behind the shoulder’ [probably near the apex of interval 7], with a ‘large, shiny, black round tubercle’}; apex of interval 5 with a scarcely distinct bare patch (apparently a very distinct, much larger round patch on P. efflatouni ); elytra lacking minute granules (‘there are also many other minute granules on the elytre’); elytra, in lateral view, nearly flat, upper point at a lower level than the upper point of the pronotum (elytra, according to Fig. 2 , slightly convex on dorsum); ventrites with distinct bare spots (no bare spots cited for P. efflatouni ).

Pachycerus sahelicus sp. nov. is sympatric with P. opimus and P. vestitus . Some specimens of P. sahelicus sp. nov. were found in collections identified as P. opimus : the simple scales of P. sahelicus sp. nov. enable an immediate distinction between these two species. Moreover, P. opimus is larger, its head has a small prominent tubercle above the eyes, and the pronotum is regularly convex, with dense small granules, and a narrow, continuous median furrow, often with a minute median keel in its centre; the elytra near the apex have several small granules. Pachycerus vestitus has long, raised setae on the whole body, including on the rostrum and above the eyes. The Madagascan P. badeni has the dorsum of the rostrum depressed between the dorsolateral and central ridges, the pronotum has two distinctly expanded lateral humps, and the elytra lack semierect setae.

Etymology: From the African region of the Sahel, where all the known specimens were originated.

Distribution and ecology ( Fig. 108 ): All the known specimens of the new species were found in the central and western part of Sahel, from western Sudan to Senegal. No documented data about their biology are available; some specimens were found on rice twigs, but it does not seem likely that this is the host plant of this species, as Cleonini are not usually associated with monocots.

Figures

Figure 70. Pachycerus efflatouni (Tewfik, 1942). Reproduction of the original drawings (from Tewfik, 1942: 173; ‘Fig. 1: Dorsal view. – Fig. 2: Lateral view. – Fig. 3: The antenna. – Fig. 4: Middle left leg. – Fig. 5: Last tarsal segment of middle left leg, ventral aspect. – Fig. 6: Quinquefid scale-like hair. – Fig. 7: Bifid scale-like hair. – Fig. 8: Fid-like scaly hair’).

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 71–84. Pachycerus sahelicus sp. nov., holotypus: body (71, 72); rostrum (73, 74); pronotum (76); antenna (80); detail of elytral scales (75); ventrites (77); sternite VIII (84); hemisternite (81); spermatheca (79). Pachycerus sahelicus sp. nov., paratypus: aedeagus (78, 82, 83). Scale bars: 71, 72, 5 mm; 77, 2 mm; 73, 74, 76, 1 mm; 78, 80, 81, 83, 84, 0.5 mm; 79, 82, 0.2 mm.

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.