Heisonyx Marshall, 1947

Borovec, Roman, Colonnelli, Enzo & Osella, Giuseppe, 2009, On the South African genus Heisonyx (Coleoptera: Curculionidae: Entiminae), Acta Entomologica Musei Nationalis Pragae 49 (2), pp. 841-860 : 842-844

Heisonyx Marshall, 1947

Type species. Heisonyx vitticollis Marshall, 1947 by original designation.

Redescription. Body length: 1.6–2.8 mm.

Integument black, legs and antennae sometimes brownish. Whole body very densely covered by regularly rounded, recumbent, longitudinally striate scales. Elytra with one regular row of slanted to erect, hairlike to clavate scales. Scales whitish, greyish or light brownish with irregular or V-shaped dark brownish spots ( Figs. 1, 2 , 4–8 ).

Rostrum wider than long, feebly tapering apically. Epifrons narrowing toward apex, with straight sides, at base only slightly narrower than distance between anterior edges of eyes, with feebly or even hardly visible V-shaped transversal groove separating it from rest of head in dorsal and lateral view. Epistome very small, sometimes hardly visible, U-shaped, separated from densely scaled frons by narrow raised line. Antennal scrobes in dorsal view open, clearly visible apically from above, in lateral view appearing as clearly limited furrows, feebly curved, directed toward dorsal half of eyes without reaching eyes and separated from them by wide stripe of scales ( Fig. 2 ). Eyes large, convex, more or less protruding from outline of head.

Antenna usually short and robust, scape strongly thickened in apical part, reaching anterior border of pronotum. Antennal funicle 5-, 6- or 7-segmented.

Pronotum wider than long, with arcuate sides. Disc without any sculpture, regularly convex.

Procoxal cavities contiguous, globular, placed at middle of prosternum.

Scutellum very small, almost invisible.

Elytra shortly oval, striae very narrow, intervals flat, elytra sometimes angulate and narrowed toward apex.

Mesocoxae semiglobular, mesosternal process narrow. Metacoxae transversal, separated by a distance wider than transversal diameter of metacoxa.

Femora edentate. Mesal edge of protibia sinuate. Apex of protibia rounded, mesally enlarged, laterally arcuate, with row of short spines and with 2–3 hook-shaped spines at mesal angle ( Fig. 16 ). Meso- and metatibia in both sexes with one short mesal spine. Metatibial corbels opened, usually with very narrow external squamose bevel. Tarsi short, last tarsomere very short with only one claw, in one of the species with trace of second claw in the form of minute basal spur.

Ventrite 1 as long as ventrite 2 and somewhat longer than ventrites 3 and 4 combined. Suture between ventrites 1 and 2 fine, sinuose, other sutures deeply inpressed, straight. Metasternal process obtuse. Entire ventral side of body densely covered by the same recumbent scales as dorsal part.

Male genitalia well sclerotised. Tegmen with long manubrium and parameroides, without armatures. Temones long.

Female genitalia. Apodeme of sternum 8 of medium length, slender, apically terminated just inside of plate. Plate narrow, umbrella-shaped, longer than wide, without margo basalis and with very slender margo apicalis with short apical setae ( Fig. 19 ). Spermatheca C-shaped, with differentiated ramus and nodulus, in most species with large corpus ( Figs. 18, 21, 22, 25, 27 ). Ovipositor with wide, feebly sclerotised hemisternite and with short or long stylus ( Figs. 17, 23, 26 ), or slender, curved, well sclerotised and without stylus ( Figs. 20, 24 ).

Differential diagnosis. Heisonyx is very similar to the genus Lalagetes Schoenherr, 1842 , sharing with it the following characters: metatibial corbels with a narrow external bevel in the sense of THOMPSON (1992), antennal scrobes visible in the anterior half from above and appearing as feeble curved furrows directed toward dorsal half of eye and not reaching it in side view, epifrons at base only slightly narrower than the space between anterior edge of eyes, and sometimes with the presence of a hardly visible, narrow, V-shaped transversal sulcus separating the rostrum from the rest of head.

Heisonyx readily differs from Lalagetes by the single tarsal claw, presence of 2–3 hookshaped spines at the mesal part of the protibia and ventrite 2 longer than the combined lengths of ventrites 3 and 4. The first two characters are exceptional in Entiminae and no other Ethiopian or Palaearctic genus that would have both of them is known to us.

Lalagetes has two claws fused in the basal half, the protibia at the mesal part with only one hook-shaped spine, and ventrite 2 as long as ventrite 3 or 4.

Tribal placement. Although MARSHALL (1947) did not assign Heisonyx to a tribe, one can infer that his intention was to include it in the Oosomini Lacordaire, 1863 , since Lalagetes was listed by LACORDAIRE (1863) and LONA (1937) in the Oosomini and was the only genus to which MARSHALL (1947: 206) compared Heisonyx . ALONSO- ZARAZAGA & LYAL (1999) listed both genera in the tribe Peritelini Lacordaire, 1863 without giving any reasons for doing so. GROBBELAAR et al. (2000) included an unnamed species, possibly a Lalagetes , in the Embrithini Marshall, 1942 , also without comments.

A better understanding of the relatioships of these two genera is difficult given the unclear phylogeny of the tribes in the Entiminae , particularly outside the Palaearctic Region. MARSHALL (1942) described the tribe Embrithini and included in it the genera of the then Oosomini with tarsal claws fused, leaving those with free claws in the Oosomini . It is evident that Lalagetes and Heisonyx clearly differ from all Palaearctic genera of the Peritelini by having a V-shaped transversal sulcus on the base of the rostrum, different shape of the antennal scrobes in dorsal and lateral view and possessing the metatibial external bevel. These characters plus the connate claws of Lalagetes are very much like those of the Embrithini , although MARSHALL (1942) did not list Lalagetes among the Embrithini . The single claw of Heisonyx , very probably resulting from a complete fusion, and its close relationship with Lalagetes allows us to consider both genera as belonging to the Embrithini (new placement).

The tribe Episomini Lacordaire, 1863 is characterized by a similar set of characters as Heisonyx and Lalagetes , in particular the V-shaped sulcus at the epifrons and the closed metatibial corbels with a squamose bevel. However, the Episomini contain large species in which the rostrum is at least slightly longer than wide and with protruding pterygia or has clear longitudinal sulci on the dorsum of rostrum and the metatibiae are often modified in males.

Figures

Figs. 1–3. Heisonyx vitticollis Marshall, 1947. 1 – habitus of the male lectotype in dorsal view; 2 – female paralectotype in lateral view; 3 – labels of the lectotype. Scale bar: 1 mm (Figs. 1, 2).

Figs. 4–7. Habitus. 4 – Heisonyx barclayi sp. nov., paratype; 5 – H. fuscus sp. nov., holotype; 6 – H. danielssoni sp. nov., holotype; 7 – H. hexarthrum sp. nov., holotype. Scale bar: 1 mm.

Figs. 8–9. Habitus. 8 – Heisonyx giustocaroli sp. nov., holotype; 9 – H. jelineki sp. nov., paratype. Scale bar: 1 mm.

Figs. 16–27. Protibia and female genitalia. 16–19 – Heisonyx vitticollis sp. nov., paralectotype: 16 – right protibia, 17 – ovipositor, 18 – spermatheca, 19 – sternum 8 in female; 20–21 – H. barclayi sp. nov.: 20 – ovipositor, 21 – spermatheca; 22 – H. danielssoni sp. nov., spermatheca; 23 – H. fuscus sp. nov., ovipositor; 24–25 – H. hexarthrum sp. nov.: 24 – ovipositor, 25 – spermatheca; 26–27 – H. jelineki sp. nov.: 26 – ovipositor, 27 – spermatheca. Scale bars: 0.25 mm (a – sternum 8; b – ovipositor and spermatheca; c – protibia).