Brachysomus (Brachysomus) fasciatus ( Stierlin, 1899 )

Yunakov, Nikolai, 2022, A review of the genus Brachysomus Schoenherr (Coleoptera: Curculionidae: Entiminae), Zootaxa 5193 (1), pp. 1-165 : 40-41

Brachysomus (Brachysomus) fasciatus ( Stierlin, 1899)

Figs. 33, 34 , 64 , 195 , 236B

Platytarsus fasciatus Stierlin, 1899: 201 . Type locality: Montenegro, Castelnuovo; Formánek 1905: 182 ( Brachysomus ); Dalla Torre et al. 1937: 173.

Redescription. Measurements: Body length 1.95–2.65 mm; width 1.10–1.50 mm. Colouration: Body dark-brown, legs and antennae light-brown. Vestiture: Body densely covered with very small scales excised apically, and long, erect, feebly widened apically, obtuse, weakly shiny setae. Shape of scales variable, slender, and deeply excised apically, or broad and weakly excised apically. Scales most densely covering sides of pronotum and elytral interstriae. Erect scales evenly covering head, concentrated in straight rows along elytral interstriae, almost as long as width of interstriae. Antennae and ventrites covered with thin pale hairs, legs with widened apically, obtuse suberect and recumbent setae. Two females from Dubrovnik, have small body and sparse vestiture.

Head: Rostrum as long as wide, parallel-sided, sharply separated from head capsule. Antennal sockets distinctly visible in dorsal view. Pterygia not projecting from outline of rostrum. Antennal scrobes sharply developed and deep, with margins divergent, reaching ventral side of rostrum. Epistome flat, without carina. Epifrons parallelsided, longitudinally convex, without carina, with deep median longitudinal sulcus, separated from vertex by distinct transverse depression, at level of antennal insertion 0.7x as wide as vertex. Vertex weakly convex, finely punctate. Eyes oval, (VW/ELD = 2), strongly, hemispherically convex. Antennae: Scape strongly curved, sharply widened along distal 1/3; funicular antennomeres: 1st 2.2x as long as wide, 2nd 2.3x as long as wide; 3rd–6th moniliform; 7th transverse; club egg-shaped.

Thorax: Pronotum transverse [PL/PW = male: 0.78–0.81 (0.79), female: 0.74–0.75 (0.74)], widest posteriad of mid length, strongly evenly convex at disc and sides, constricted anteriorly and posteriorly, densely, shallowly punctate, disc with well-developed lateral depressions. Elytra: oval to oblong-oval, strongly convex at disc and sides. Interstriae of elytra flat, 2x wider than striae. Punctures well 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 mucro. Second tarsomere weakly transverse. Fifth fore tarsomere extending beyond apical lobes of 3rd by length of the lobes.

Abdomen: First ventrite with posterior margin weakly sinuate. Male 5th ventrite transversally convex, truncate, with scattered pale hairs. Male genitalia: Aedeagus heavily sclerotized through entire length. Median lobe 1.3x longer than apodemes, parallel-sided, apex attenuate. Endophallus with fine spicules. Ventral membranes triangular, slightly sclerotized. Parameres vestigial, free, posterior margin of basal piece straight. Spermatheca: ramus and collum slightly divided at base, ramus 2x as long as collum, collum curved.

Diagnosis. Brachysomus fasciatus is very similar to B. hirtus , and can be securely distinguished by the structure of the aedeagus and shape of spermatheca. Aedeagus regarding to length of body is longer, than in B. hirtus . External differences unclear and variable. Body of B. fasciatus usually with denser cover of scales, male 5th ventrite evenly convex, not flattened on apical third; eyes more convex.

Distribution. Bosnia and Herzegovina, Croatia, Montenegro.

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

Remarks. The type series was collected by Gustav Paganetti-Hummler in Montenegro near Herzegnovi. The discovery of B. fasciatus in the Topla Valley (Slovenia, see ‘Material’ section below) needs confirmation, because this species is usually found in maritime forests.

Type material. Lectotype, ♀ (here designated) (SDEI) ‘Castelnuovo Hummler’, coll. Stierlin’, ‘Syntypus’, ‘Lectotypus, Platytarsus fasciatus Strl., Yunakov design. 2022’; the rest of syntypes labeled: ‘Paralectotypus, Platytarsus fasciatus Strl., Yunakov design.’ Paralectotypes, 39 specimens (SDEI) labeled as lectotype. 2 males and 3 females were remounted and dissected.

Additional material examined. BOSNIA AND HERZEGOVINA: 2♀, ‘Herzegovina’, ‘U. Sahlb.[erg]’ (ZIN); 1♀, ‘Herzegovina, Vall. Trebinje’ (ZIN); 1♂, 1♀, idem, 1903, O. Leonhard leg. (MTD); 1♂, ‘Herzegovina, Duži, 1903, O. Leonhard leg.’ (MTD). CROATIA: 7♂, 2♀, Ragusa [= Dubrovnik] Holdhaus leg. (NMPC, ZIN); 1♀, ‘Ragusa, Kalecsenyi’ (ZIN). MONTENEGRO: 1♂, 1♀, Castelnuovo [= Herceg-Novi], Apfelbeck leg. (ZMUH); 25♂, 22♀, idem, Paganetti leg. (ZIN, ZMUH, NHMUK, MTD); 2♂, 2♀, idem, 1910, M. Hilf leg.; 1♂, 1♀, idem, V. Zoufal leg., ex coll. Munster (ZMUN); 3♂, 1♀ ‘Dalmatien, ex coll. Munster’ ‘Dalmatien, Reitter’ (ZMUH, NHMUK). 2♀, Radostak, Holdhaus leg. (MTD); 4♂, 2♀, ‘Cattaro [=Kotor], Dalmatia’ (MTD).

Doubtful: SLOVENIA: 1♂, 1♀, ‘Topla, Paganetti’ (ZMUN) (see ‘Remarks’ above).

Figures

FIGURE 195. Brachysomus fasciatus: A: aedeagus, dorsal view; B: tegmen; C: spermatheca; D: head of male; E: antenna; F: sternite VII.

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.

FIGURES 63–70. Brachysomus, details: 63: B. hirtus, 64: B. fasciatus. 65, 66: B. ponticus. 67, 68: B. commutatus. 69: B. ponticus. 70: B. commutatus.