Afrophloeus Borovec & Oberprieler

Borovec, Roman & Oberprieler, Rolf G., 2013, Afrophloeus, a new genus of African weevils of the tribe Embrithini (Coleoptera: Curculionidae: Entiminae), with description of a new species and notes on the composition of Embrithini, Zootaxa 3693 (3), pp. 365-378 : 367-372

Afrophloeus Borovec & Oberprieler , gen. n.

Type species: Trachyphloeus spathulatus Boheman in Schoenherr, 1843.

Diagnosis. Small Embrithini , less than 3.5 mm long, with short, strongly transverse rostrum; epifrons nearly isodiametric, at base significantly narrower than space between anterior margins of eyes, separated from head by distinct transverse sulcus; pronotum short, very broad; elytra short, robust; antennae robust, scapes as long as funicle + club; apex of front tibiae with 7 spines of different length and shape; tarsal claws fused in basal half, then divergent.

Description. Length 2.3–3.3 mm.

Colour and vestiture. Ground colour of body black, antennal clubs and tarsi paler, reddish brown, apical tibial spines and claws dark to pale reddish, in some specimens spines blackish. Vestiture of body consisting of very dense, erect, smaller, thinly stalked setae with bent, imbricate scale-like apices and of sparse, semi-erect, larger, mostly apically flat and striate setae, all trapping a thick layer of exudate between them to completely obscure the cuticle; antennal clubs with dense, short, very fine, appressed cylindrical setae only; legs and underside with shorter (normal), tessellate to imbricate scales. Scale-like apices of small body setae broadly oval, some opalescent to greenish iridescent, 6 to 7 across one elytral interstria. Large body setae subspatulate to spatulate, striate, slightly shorter than half of interstrial width, sparsely irregularly scattered on rostrum, head and pronotum, in single sparse rows on interstriae; on tibiae and funicles longer, weakly to non-striate, sometimes cylindrical with blunt to sharp tip; pale brownish-grey or blackish in colour. Colour pattern of body ( Figs. 1–3 ) various, in fresh specimens greyish, brownish to blackish, in older specimens usually obscured by colour of soil adhering to exudate among vestiture; elytra on disk with distinct to indistinct chevron pattern of three dark and three pale V-shaped bands, on declivity with irregular smaller dark and pale spots except sutural interstriae pale only; pronotum with faint, pale, broad median and lateral stripes interrupted by darker patches; head with pale subtriangular, median patch on vertex and irregular one above each eye ( Figs. 7–9 ).

Rostrum robust, 1.3–1.5 x broader than long, in dorsal view ( Figs. 7–9 ) at base abruptly slightly broader than head, subparallel-sided to slightly tapering towards antennal insertions, at apex broadly rounded; in lateral view vaulted, well separated from head. Epifrons about isodiametric, short and narrow, at base about 0.6 x as broad as rostrum, sides feebly rounded, medially longitudinally somewhat depressed, posteriorly higher than vertex, dorsally distinctly separated from head by wide, deep, crescentic transverse sulcus. Frons squamose, with 3–4 pairs of stout apical setae. Epistome small but distinct, triangular, posteriorly sharply carinate, asquamose. Antennal sockets in dorsal view well visible in anterior two-thirds of rostrum, narrowly reniform ( Figs. 7–9 ); in lateral view placed near dorsal margin of rostrum, posteriorly enlarged dorsad, sharply set off from densely squamose rostrum all around, not forming distinct scrobe posteriorly, separated from anterior margin of eye by about eye diameter. Head very broad, almost flat but slightly raised above eyes. Eyes small, subcircular in outline, almost flat and vertical, in dorsal view hardly visible, not prominent from outline of head ( Figs. 7–9 ), in lateral view placed closer to dorsal border of head. Antennae ( Figs. 10, 12, 14 ) short and robust. Scapes relatively long, about as long as funicle + club, reaching beyond anterior margin of pronotum in repose, slightly bisinuate, apically inflated with posterior edge in some species moderately to strongly abruptly dilated. Funicles 7- to 4-segmented, with segment 1 enlarged, subglobular, the rest obconical, progressively shorter and broader towards club. Clubs broad and short, segment 1 conspicuously largest, comprising 1/2 to 2/3 of club length. Mandibles trisetose, scars flat, vertically oblong. Prementum densely strongly setose, submentum with a median pair of long, flat, striate setae.

Pronotum shortly transverse, 1.7–2.1 x broader than long, sides slightly roundly inflated, broadest in anterior third or in middle, from there strongly tapering anteriad and more gradually posteriad, anteriorly sometimes faintly constricted. Disc regularly vaulted, sometimes with faint, shallow, median depression. Base moderately to strongly arched. Anterior border in lateral view very feebly sinuate, not forming ocular lobes, with dense row of short, broad scales directed anteriad. Procoxal cavities contiguous, round, in middle of prosternum; procoxae subglobular. Scutellar shield invisible. Elytra subquadratic, 1.1 x longer than broad, subparallel-sided, bases moderately to strongly arched, sides feebly rounded, at apex jointly broadly rounded, at interstria 9 with feeble or well developed posthumeral callus well visible in dorsal view in some species; 10-striate, striae narrow, finely punctate; interstriae somewhat convex. Mesocoxae semiglobular, narrowly separate, mesosternal process narrow, not reaching posterior margin of mesocoxae. Metacoxae shortly transverse, separated by about 1.5 x their width. Femora medially slightly inflated, unarmed. Tibiae short, robust, straight; protibiae ( Figs. 11, 13, 15 ) apically rounded, with 7 large, mostly separate spines, the inner one short and straight, the next two long and curved inwards, the next two shorter and straight, sometimes fused at base, the outer two also short and straight, widely separate; mesotibiae apically with 5 similar but more subequal spines; metatibiae apically truncate, with 2 large, curved inner spines and narrow, squamose corbel fringed by 10–14 stout short setae. Tarsi long and slender, segment 1 about as long as 2+3, 2 transverse, 3 slightly broader than 2 and bluntly bilobed, underside sparsely coarsely setose, not forming distinct segmental pulvilli, segment 5 (onychium) longer than 2+3, cylindrical and curved down. Claws solidly fused and subparallel in basal half, then strongly divergent.

Abdomen ventrally subtriangular, about 1.1 x broader than long; ventrite 1 in middle about as long as 2–4, laterally about as long as 2, 2 as long as 3–4, 5 apically subtruncate; suture between 1 and 2 curved, narrow and fine, others straight, wide and deep; ventrites 3 and 4 each with single transverse row of spatulate, striate setae; ventrite 1 in males shallowly concave, in females slightly convex, ventrite 5 in males shorter, trapezoidal, in females longer, subtriangular.

Sexual dimorphism. Sexes externally indistinguishable except for slight differences in shape of ventrites 1 and 5.

Genitalia. Penis ( Figs. 16–17 ) short, well sclerotised, temones 2.5 x longer than body of penis and 3.0–3.5 x longer than tegminal manubrium; endophallus short, inside very finely spiculate and with pair of larger, elongate, compressed sclerites at base. Tegmen ( Fig. 18 ) with slender complete ring but without parameres. Sternite IX ( Fig. 19 ) with spiculum gastrale moderately long, anteriorly curved and tapered, posteriorly with fused basal arms; apical plate absent. Gonocoxites ( Fig. 21 ) simple, short, broad, depressed, evenly tapered apicad, with very short, apical stylus with tuft of 3–4 stiff setae. Sternite VIII ( Fig. 20 ) with long, slender apodeme (spiculum ventrale) terminating just inside basal plate, plate short and broad, umbrella-shaped, with basal margin ill-defined and apical margin armed with setae. Spermatheca ( Figs. 22–23 ) large, crescentic, with slender cornu and large, elongate corpus; ramus and nodulus differing between the species; spermathecal duct inserted on ventral side of bursa.

Etymology. The genus name is derived from Africa, the home of the genus, and phloeus, the Greek word for bark as used in the compound name of Trachyphloeus , the genus with which it was confused. The name is masculine in gender.

Biology. The adult weevils feed on a large variety of plants, both native and cultivated, having been reported to damage seedlings of crops such as brassica, canola, carrot, chicory, clover, cucumber, green-pepper, lucerne, medic, potato, radish, sunflower and vetch. The larvae have not been recorded but probably feed on the roots of also a variety of different plants. The small size, cryptic habitus and lack of host specificity of the adults appear to facilitate their introduction into areas outside their native ranges with crop transports.

Distribution. The genus is native in south-western South Africa, but two species are apparently introduced in the northern parts of the country (e.g. the Gauteng province) and one also in Australia ( Figs. 24–25 ).

Remarks. Afrophloeus currently comprises three species, one of them described here. Although superficially similar to Trachyphloeus , it differs distinctly from this genus and all Trachyphloeini (sensu Borovec 2009) in possessing proper metatibial corbels and a very narrow epifrons (the sides not touching the inner margin of the eyes). Already Seidlitz (1868) recognised that Afrophloeus spathulatus and A. squamifer do not fit into Trachyphloeus due to having dorsally placed antennal sockets, small and lateral eyes, thick funicles, proper metatibial corbels and basally connate claws, but although he suggested that they belong in a different genus, he did not transfer them to another or describe a new one for them but provisionally retained them (as a single species) in Trachyphloeus . From most other embrithine genera Afrophloeus differs in its narrow epifrons, in the smooth, even lateral contour of its rostrum and head including the flat eyes, in its broad and robust scapes and in the seven spines on the apex of its protibiae. It is most similar to Lalagetes , Heisonyx and the smaller species of Ischnobrotus Aurivillius , all less than 3.5 mm long. It agrees with Lalagetes and Heisonyx in having the rostrum distinctly broader than long, the intermetacoxal process of ventrite 1 obtuse and broader than a metacoxa and ventrite 1 about twice as long as 2, but it differs from them in the following features: epifrons separated from head by a wide transverse sulcus with ill-defined borders (the sulcus narrow, sharply edged in Lalagetes and Heisonyx ); epifrons about as long as broad and at base distinctly narrower than distance between anterior borders of eyes (longer than broad and at base about between eyes in Lalagetes and Heisonyx ); rostrum, eyes and head in dorsal view forming a continuous line (distinctly set off from each other in Lalagetes and Heisonyx ); eyes small and flat, hardly visible in dorsal view (convex, well visible in dorsal view in Lalagetes and Heisonyx ); scapes short, broad and robust (long and slender in Lalagetes and Heisonyx ); funicle segments short, transverse (long and slender in Lalagetes and Heisonyx ); clubs barely broader than last funicle segment and approximated to it (distinctly broader than and distinctly separated from last funicle segment in Lalagetes and Heisonyx ); pronotum short and broad, at least 1.7 x broader than long (narrower, at most 1.5 x broader than long in Lalagetes and Heisonyx ); apex of front tibiae with 7 slender spines, some of them long (with two long and five short spines in Heisonyx , with fringe of bristles or setae in Lalagetes ). Afrophloeus is readily distinguishable from Ischnobrotus by the following characters: head and rostrum dorsally separated by wide transverse sulcus with ill-defined edges (sulcus narrow, sharply edged in Ischnobrotus ); epifrons about as broad as long (distinctly longer than broad in Ischnobrotus ); frons squamose (glabrous in Ischnobrotus ); protibiae short and robust, apically armed with 7 spines of different lengths (long and slender, apically with fringe of fine, short, mostly yellowish setae in Ischnobrotus ); eyes flat, small, continuous in outline with rostrum and head in dorsal view (large, feebly or strongly convex, clearly set off in outline from rostrum and head in dorsal view in Ischnobrotus ); scapes short, robust, barely exceeding anterior pronotal border in repose (long, slender, well exceeding pronotal border in Ischnobrotus ); funicle segments short, transverse (longer and slender in Ischnobrotus ); clubs barely broader than and approximated to last funicle segment (distinctly broader and distinctly separated in Ischnobrotus ); pronotum at least 1.7 x broader than long (at most 1.4 x broader than long in Ischnobrotus ); elytra robust, rectangular (slender, oval to elongate in Ischnobrotus ).

The intraspecific variation in the number of funicular segments in two of the species ( A. spathulatus and A. dilaticornis ) is remarkable as this is a rare phenomenon in weevils. We know of only one other example in Entiminae , the Tunisian Trachyphloeus difformis Formánek , of which the type series includes specimens with 6- and 7-segmented funicles (Borovec 2013), and of another in Ceutorhynchini , in which some specimens of Ceutorhynchus liliputanus Schultze have the same variability in the number of funicle segments (J. Krátký, pers. comm.).

Figures

FIGURES 1 – 15. Habitus and structural details of Afrophloeus gen. n. 1. A. spathulatus (Boheman), ♀, Swartville, dorsal habitus; 2. A. dilaticornis sp. n., paratype ♀, Alexandria, dorsal habitus; 3. A. squamifer (Boheman), ♂, Marion Bay, dorsal habitus; 4. A. spathulatus (Boheman), ♀, Swartville, lateral habitus; 5. A. dilaticornis sp. n., paratype ♀, Alexandria, lateral habitus; 6. A. squamifer (Boheman), ♀, Marion Bay, lateral habitus; 7. A. spathulatus (Boheman), ♂, Kleinriviersberg, head, dorsal view; 8. A. dilaticornis sp. n., paratype ♂, Alexandria, head, dorsal view; 9. A. squamifer (Boheman), ♂, Marion Bay, head, dorsal view; 10. A. spathulatus (Boheman), ♀, Swartville, left antenna, dorsal view; 11. A. spathulatus (Boheman), ♂, Kleinriviersberg, left protibia and tarsus, dorsal view; 12. A. dilaticornis sp. n., paratype ♀, Alexandria, left antenna, dorsal view; 13. A. dilaticornis sp. n., paratype ♂, Alexandria, left protibia and tarsus, dorsal view; 14. A. squamifer (Boheman), ♂, Marion Bay, left antenna, dorsal view; 15. A. squamifer (Boheman), ♂, Marion Bay, left protibia and tarsus, dorsal view. Scale bars 1 mm for 1 – 6, 0.5 mm for 7 – 9, 0.25 mm for 10 – 15.

FIGURES 16 – 23. Genitalia of Afrophloeus gen. n. 16. penis of A. spathulatus (Boheman), dorsal view; 17. penis of A. spathulatus (Boheman), lateral view; 18. tegmen of A. spathulatus (Boheman), dorsal view; 19. sternite IX of male A. spathulatus (Boheman), dorsal view; 20. sternite VIII of female A. spathulatus (Boheman), dorsal view; 21. ovipositor of A. spathulatus (Boheman), dorsal view; 22. spermatheca of A. spathulatus (Boheman); 23. spermatheca of A. squamifer (Boheman). Scale bars 0.5 mm for 16 – 20, 0.25 for 21 – 23.

FIGURES 24 – 25. Distribution of Afrophloeus species. 24. South Africa; 25. South Australia (○ — A. spathulatus (Boheman), ■ — A. squamifer (Boheman), ∆ — A. dilaticornis sp. n.).