Lyalinus, Borovec, 2018

Borovec, Roman, 2018, Lyalinus, a new genus of Cneorhinini from Burkina Faso (Coleoptera: Curculionidae), Acta Entomologica Musei Nationalis Pragae 58 (1), pp. 25-30 : 26-28

Lyalinus gen. nov.

Type species. Lyalinus bimaculatus sp. nov. by present designation.

Diagnosis. Small genus belonging to Entiminae . Rostrum more than twice as long as wide, equally wide at base and at apex; epifrons separated posteriorly from head by transverse sulcus; frons not separated posteriorly; epistome not differentiated; mandibles multisetose; scrobes laterally placed, furrow-shaped, glabrous, clearly edged, directed to ventral border of eye; eyes subdorsal, vertex slender, vaulted, separated from head behind eyes by transverse sulcus; scape short, slightly exceeding anterior border of eye, as long as funicle; tergite VII in both sexes with concave anterior border; metatibia with wide, densely squamose corbel; ventrites subtriangular with ventrite 2 only slightly longer than ventrite 3 or 4, ventrite 5 narrowly tapered; tegmen lacking parameres; female sternite VIII with plate large, arrow-shaped with ill-defined posterior border and extending along apodeme.

Description. Body length 3.9–5.2 mm.

Body dark brownish to blackish. Dorsal part of body densely covered with regularly rounded appressed isolated scales, greyish with distinct pearly sheen. Ventral part of body covered by the same vestiture, appressed scales on ventrites smaller, denser and oval. Each elytral interval with inconspicuous row of very short subspatulate setae, semiappressed on disc and apical declivity, barely visible in lateral view. Antennal club densely setose; funicle and scape with very small, long oval appressed scales; femora with appressed scales identical to those on dorsal part of body; tibiae and tarsi with appressed oval scales and short, semierect bristle-shaped yellowish setae.

Rostrum 2.4–2.6× as long as basal width, base and apex of equal width, 0.9× as long as pronotum in lateral view, equally wide and shaped in both sexes. Epifrons widest at base, wider than rostrum in dorsal view, evenly tapered apicad from base with straight sides, distinctly carinate laterally, extending apically to level of anterior border of scrobes, flat, with median longitudinal slender carina along whole length, posteriorly separated from head by arched carina creating edge of sulcus separating rostrum from head, laterally reaching below middle of eye. Rostrum dorsally slightly widened before antennal insertion, then subparallel-sided; laterally with ventral border regularly weakly curved and dorsal border in basal two thirds flat to slightly concave and in apical third weakly declined at level of antennal insertion, straight apically. Frons large, glabrous, moderately shiny, not separated posteriorly from epifrons, with 7–8 pairs of long, stout setae prominent laterally and 6–8 pairs of similar setae placed dorsally. Epistome not differentiated. Mandibles small, slender, projecting anteriorly, armed with one small blunt inner tooth, lacking scales, with 6–8 laterally prominent fine setae; deciduous mandibular processes moderately long, straight, unarmed, narrowest at base, sharply carinate along entire external margin, situated at outer part of mandibles; in lateral view evenly triangularly tapered anteriad with sharp tip. Scrobes placed laterally, in dorsal view visible as narrow parallel furrows before the middle; laterally clearly visible along whole length as narrow, straight glabrous furrow directed from dorsal part of rostrum to ventral part of eye, with conspicuous dorsal edge and visible, but less prominent ventral edge. Rostrum ventrally glabrous, with several sparse slender appressed scales. Head wide and short, distinctly enlarged posteriad, behind eyes smooth, vaulted, separated from vertex by transverse double arched sulcus. Vertex evenly enlarged posteriad, at base as wide as dorsal width of eyes, distinctly convex with narrow median longitudinal glabrous stria. Eyes large, subdorsal, convex, distinctly prominent from outline of head; laterally a little higher than base of rostrum and much higher than rest of head.

Antennae moderately short. Scape slender, a little exceeding anterior border of eye when held against rostrum, as long as 7-segmented funicle; funicle segments 1–3 long and conical with segment 1 longest, the others isodiametric to slightly wider than long; club with segment 1 subconical, narrow at base and evenly enlarged apicad, comprising half of club length.

Pronotum 1.3–1.4× wider than its width at posterior border; disc regularly convex without any furrow, keel or depression; base slightly arched. Laterally anterior border of pronotum straight without ocular lobes or setae. Procoxal cavities contiguous, round, placed at midlength of pronotum; procoxae subglobular.

Scutellum very small, triangular.

Elytra long oval, 1.2–1.3× as long as wide, at base weakly constricted, without humeral calli, at base equally wide as base of pronotum with slightly arched base, widest at midlength, apically evenly tapered; laterally convex, slope only just overhanging weakly elongate apex. Elytra 10-striate, striae punctate, intervals flat and wide. Mesocoxae semiglobular, mesosternal process very narrow, about as wide as one tenth of mesocoxal width, not reaching posterior margin of mesocoxae. Metacoxae semiglobular, metaventral process weakly rounded, a little wider than half of transverse diameter of metacoxa. Tergite VII in males short and broad, translucent, with sclerotised very narrow margins, apically concave; tergite VIII in males well sclerotised, bowl-shaped, apically truncate. Tergite VII and VIII in females larger than those in males, weakly sclerotised; tergite VII subtrapezoidal, apically shortly concave; tergite VIII subtriangular, apically rounded.

Legs moderately robust. Femora faintly swollen, unarmed. Protibiae laterally straight, inside sinuate, denticulate at apical half with 6–7 well visible brownish teeth, apically rounded and distinctly enlarged inside, densely fringed by yellowish short fine setae, mucronate. Metatibiae with apical surface large, oval, glabrous and with wide, conspicuous, densely squamose corbel fringed externally and internally with long and dense yellowish setae. Tarsi moderately robust, with segment 3 distinctly wider than segment 1 and 2; onychium short; claws solidly fused in basal half, unequally long.

Abdomen ventrally subtriangular, distinctly tapered apicad with almost straight sides, 1.1× as wide as long; ventrite 1 in middle more than 3× as long as ventrite 2, behind metacoxa slightly longer than ventrite 2; ventrite 2 slightly longer than ventrite 3 or 4 and shorter than ventrites 3 and 4 combined; ventrite 5 in males subtrapezoidal, short, obtuse at apex, in females subtriangular, longer, pointed at apex, with weakly concave sides. All sutures straight, deep and moderately wide.

Sexual dimorphism. Sexes externally indistinguishable except for slight difference in shape of ventrite 5.

Male terminalia. Penis slender, long, well sclerotised, temones 1.5× as long as body of penis; endophallus short with two long sclerites. Tegmen with wide small ring lacking parameres, manubrium almost three times as long as diameter of ring, one third as long as penis temones. Sternite IX with spiculum gastrale long, anteriorly curved and enlarged to narrow translucent plate, posteriorly with fused basal arms; sternite VIII with hemisternites slender, curved.

Female terminalia. Sternite VIII with apodeme widest at midlength with transverse anterior bar, apodeme Y-shaped posteriorly, terminating just within basal plate; basal plate arrow-shaped, longer than wide, about third of length of sternite, pointed with apical margin developed and basal margin ill-defined, apex carrying two separate, anteapical tufts of setae. Gonocoxites simple, wide and flat, regularly tapered apicad, with short apical styli bearing apical setae. Spermatheca with regularly curved slender cornu, elongate corpus, short and hardly visible ramus and long nodulus.

Etymology. The new genus is cordially dedicated to Christopher H. C. Lyal, an eminent British curculionologist, and the name is of male gender.

Distribution. Known only from Burkina Faso.

Species included. The genus is described as monotypic.

Remarks. The newly described genus has multisetose mandibles, short antennal scapes, laterally placed scrobes of the ‘brachyderinae’ type, lateral pronotal border lacking vibrissae, developed metatibial corbels and connate claws, which is a complex of characters typical for the tribe Cneorhinini . In this tribe only three other genera have a rostrum longer than wide as seen in Lyalinus gen. nov. – Euonychus Marshall, 1923 , Fleurops Hustache, 1931 , and Synaptocephalus Faust, 1891 . These three genera are rather different and apparently do not form a monophyletic group. The genus Euonychus includes two known and another two undescribed species, all restricted to South Africa and Namibia (Borovec, unpublished data).

Fleurops is a monotypic genus known from Uganda, the Democratic Republic of Congo, Burundi and Tanzania ( KANIA & STOJCZEW 1999). Lyalinus gen. nov. shares the moderately similar body shape and legs, and also the pear-shaped antennal clubs, but differs most clearly in the rostrum and head structure.

Its long rostrum and the subdorsal eyes with slender vertex make Synaptocephalus the most similar genus to Lyalinus gen. nov. Synaptocephalus includes four species known from the eastern part of Africa: Zimbabwe, Zambia, Tanzania, and Sudan (Borovec, unpublished data). It is possible to recognize all four genera based on the characters stated in the Table 1 .

Except for the multisetose mandibles, laterally placed scrobes and short antennal scapes, Lyalinus gen. nov. resembles in its general appearance some Embrithini genera with an elongate rostrum, namely the genera Bicodes Marshall, 1908 , Goniorhinus Faust, 1889, Holorygma Marshall, 1927 , Lecanophora Aurivillius, 1912 , Neobicodes Hustache, 1929 , Sympiezorhynchus Schoenherr, 1842 , and Zeugorygma Marshall, 1906 . From all these genera Lyalinus gen. nov. can also be distinguished by characters stated in the Table 1 .