Brachysomus (Brachysomus) subtilis Yunakov, 2006

Yunakov, Nikolai, 2022, A review of the genus Brachysomus Schoenherr (Coleoptera: Curculionidae: Entiminae), Zootaxa 5193 (1), pp. 1-165 : 42-43

Brachysomus (Brachysomus) subtilis Yunakov, 2006

Figs. 35, 36 , 198 , 236B

Brachysomus subtilis Yunakov, 2006: 299 . Type locality: Montenegro, Dobrota.

Redescription. Measurements: Body length 1.50–2.37 mm, width 0.90–1.37 mm, in holotype 1.92 mm and 1.00 mm, respectively. Colouration: Body brown, legs and antennae lighter. Vestiture: Body densely covered with weakly metallic, elongate, excised apically, recumbent scales and short, weakly spatulate, obtuse, suberect setae. Scales on

pronotum and head strongly-, on elytra weakly excised and broad. Sides of pronotum and elytral interstriae very densely covered with scales. Setae 0.5 as long as width of interstriae. Antennae and ventrites light brown, with fine, light pubescence, legs light brown, with narrowly spatulate setae.

Head: Rostrum as long as wide (RL/RW = 1), parallel-sided, sharply separated from head capsule. Antennal sockets distinctly visible in dorsal view. Pterygia weakly projecting from outline of rostrum. Antennal scrobes sharply developed and deep, with divergent margins, reaching ventral side of rostrum. Epistome flat, without carina. Epifrons parallel-sided, strongly longitudinally convex, without carina, with deep median longitudinal sulcus, separated from vertex by weak but well visible transverse depression. Vertex weakly convex, finely punctate. Eyes oval (VW/ELD in males = 1.61–1.63, in females = 2.08–2.18), strongly hemispherically convex, highest at middle.

Antennae: Scape gently curved, strongly widened along distal 1/3; funicular antennomeres: 1st and 2nd elongate (L/W = 2.0–2.3), 1st as long as 2nd, but noticeably larger than 2nd; 3rd–6th as long as wide; 7th transverse; club egg-shaped.

Thorax: Pronotum transverse [PL/PW = 0.72–0.80 (0.86)], widest at middle, strongly and evenly convex at disc and sides, constricted anteriorly and posteriorly, densely, shallowly punctate. Elytra: in male oblong-oval (EL/EW = 1.28–1.33), in female broadly-oval (EL/EW = 1.22–1.23), disc with well-developed lateral depressions. Interstriae of elytra flat, 2x wider than striae. Punctures slightly separated. Spaces between punctures very weakly concave, somewhat narrower than diameter of puncture. Legs: Fore tibiae straight, with apical external angle not protruding. Hind tibiae with strong, thorn-shaped mucro. Second tarsomere weakly transverse (L/W =0.60). Fifth fore tarsomere extending beyond apical lobes of 3rd by 0.60 length of the lobes.

Abdomen: First ventrite with posterior margin weakly sinuate. Male 5th ventrite flat, widely rounded apically, with scattered pale hairs. Male genitalia: Aedeagus heavily sclerotized through entire length; median lobe 1.2x longer than apodemes, evenly narrowed apically, apex acute. Ventral membranes triangular, slightly sclerotized. Parameres vestigial, posterior margin of basal piece straight. Spermatheca: ramus and collum connate at base, ramus 2x as long as collum.

Diagnosis. Brachysomus subtilis is very similar to B. fasciatus and B. hirtus , differing by the shorter suberect setae on the elytral interstriae, weakly visible median longitudinal sulcus on epifrons, lack of lateral depressions on disc of pronotum, and strong, long, thorn-shaped mucro on male tibiae.

Distribution. Montenegro (coast of Boka Kotorska Strait).

Bionomics. This species inhabits leaf litter in xerothermic coastal forests from 200–1000 m a.s.l.

Type material. MONTENEGRO: Holotype,♂ (NMPC): ‘Dobrota, Mai. 1916’, ‘Collectio Dr Jureček, H. Jurečková’. Paratypes: 2♂, labeled as holotype (NMPC); 1♀, ‘Dobrota, Juni 1916’, ‘Collectio Dr Jureček, H. Jurečková’ (NMPC); 13♂, 6♀, ‘Boc.[ca] di Cattaro (= Boka Kotorska Strait), Rittm. Matcha’ (NMPC, ZIN); 2♂, 2♀, ‘Boc.[ca] di Cattaro, April, 1916’ (NMPC); 3♂, ‘Cattaro (= Kotor), 10.7.1916’, ‘Collectio Dr Jureček, H. Jurečková’ (NMPC); 1♂, ‘Cattaro’, ‘U. Sahlb.[erg]’, ‘1066’, ‘ Br. fasciatus var.’ (NMPC); 8♂, 1♀, ‘Dalmatia, J. Matcha’ (ZMUH); 1♂, ‘Montenegro westliches, Reitter’ (NMPC); 3♂, 1♀, ‘Cattaro, Dal.[matia], 1916’, ‘ Brachysomus hirtus Boh. ’ (NMPC).

Figures

FIGURE 198. Brachysomus subtilis: A: aedeagus, dorsal view; B: tegmen; C: spermatheca; D: body; E: head of male; F: antenna G: fore tibia of male; H: hind tibia of male; I: scales of elytra.

FIGURE 236. Occurrence map of Brachysomus: A: B. hirtus; B: Brachysomus hirtus species group. Red triangles indicate occurrence of males of B. hirtus.

FIGURES 31–36. Brachysomus, dorsal habitus:31: B. hirtus, male. 32: B. hirtus, female. 33: B. fasciatus, male. 34: B. fasciatus, female. 35: B. subtilis, male. 36: B. subtilis, female.