Bruchidius subtilis, Delobel, 2016

Delobel, Alex, 2016, Three newBruchidius species from Eastern and Southern Africa (Coleoptera: Chrysomelidae: Bruchinae), Acta Entomologica Musei Nationalis Pragae 56 (1), pp. 265-273 : 270-272

Bruchidius subtilis sp. nov.

(Figs 7–9)

Type locality. Kenya, Taita-Taveta Co., Taveta, 750 m a.s.l.

Type material. HOLOTYPE: J (dissected [Br.M.P. 55]), ‘ KENYA, Afr. Orient.Anglaise / Taveta / Alluaud & Jeannel / mars 1912 750m st. 65 // Holotype // Bruchidius subtilis n. sp. / Delobel des. 2015’ ( MNHN) . PARATYPES: 3 JJ (all dissected), ʻVoi, 8-18.xi.1996, M. Snizekʼ ; 2 JJ (1 dissected), 1 ♀ (dissected), ʻVoi, 22.xi-2.xii.1996, Mi. Haladaʼ ; 10 JJ (7 dissected), 9 ♀♀ (1 dissected [02814]), ʻVoi, 11-14.iv.1997, Ma. Haladaʼ ; 1 J, ʻVoi, 11-14.iv.1997, M. Snizekʼ ; 7 JJ (4 dissected [02014, 02114, 06709]), 1 ♀, ʻVoi, 23.iii-4.iv.1997, Ma. Haladaʼ ; 4 JJ (1 dissected [02214]), ʻVoi, 23.iii-4.iv.1997, M. Snizekʼ ; 1J 3♀♀, ʻVoi, 1-5.iv.1997, M. Snizekʼ ; 1J (dissected [02714]), 3♀♀, ʻVoi, 23.xi.1997, M. Snizekʼ (all in OLML) ; 1 J (dissected [06009]), ‘ SOUTH AFRICA, KNP / Crooke’s Corner nr Pafuri, 2.ii.1994, E. Grobbelaar ( NCIP) ’.

Description. Length: 3.0– 3.2 mm; width: 1.6–1.8 mm.

Body moderately stout, last visible tergite slanted about 25° from vertical. Integument reddish brown, with four anterior legs and antennal segments I–VII testaceous, VIII darkened, IX–X dark brown to black, XI dark testaceous (black in four male paratypes); elytra more or less darkened at humerus, along suture, and near apex; sutural drop-shaped spot may be absent (in a single male), or spread over first three interstriae. Vestiture well covering integument, mostly sand-colored, lighter on sides of pronotum, along mid-line and sometimes a pair of small spots laterally; on elytra vestiture varies from almost uniformly light to black spotted; last visible tergite light, with white basal triangle.

Male. Head short, moderately constricted behind eyes; eyes large, bulging, maximum head width 1.4 times width behind eyes; ocular sinus comparatively shallow; eyes separated by only 0.32 times head width including eyes; face moderately wide, distance between posterior rim of eyes and apex of clypeus / distance between eyes = 2.0; eye moderately cleft, width at bottom of sinus composed of 7 ommatidia; post-ocular lobes hardly visible; frontal carina obsolete; inter-ocular tubercle distinct, shining; face with dense punctation, vanishing on alutaceous clypeus. Antenna (Fig. 9) not reaching to posterior angles of pronotum; antennal segments I–III subcylindrical, segment IV slightly widened at apex, segment V and following subrectangular, transverse, XI oval (L/W = 1.17). Length of antennomeres: 1.6: 1.0: 1.1: 1.1: 1.2: 1.1: 1.3: 1.2: 1.2: 1.2: 1.8.

Pronotum trapezoidal, with maximum width at base (W/L = 1.4), its sides almost straight,

Genitalia and antenna of Bruchidius subtilis sp. nov.: 7 – median lateral lobes; 9 – male antenna.

not widened behind eyes; without oblique impression on each side of basal lobe; disc strongly alutaceous, with dense shallow punctation. Elytra 1.04 times longer than wide together, their sides regularly widened to mid-length; disc regularly convex; two minute teeth at base of striae 3 and 4, closer to each other than to elytron base; humeral callus moderately developed, alutaceous; striae very shallow, interstriae flattened, with dense micro-punctation, without visible alignment of larger punctures. Hind femur moderately incrassate, more than twice wider than middle femur; mesoventral margin with small acute preapical denticle; hind tibia apically strongly widened, with ventral carina complete, lateral and dorsomesal strong, reaching base; apex of tibia with mucro as long as tarsomere I width, lateral denticle about half mucro length.

Abdomen with ventrite V moderately emarginated, its length medially less than half as long as laterally; ventrite I with large, pear-shaped patch of dense setae in basal half of ventrite. Last visible tergite shield-shaped, only slightly longer than wide, with apex moderately turned under.

Genitalia. Median lobe (Fig. 7) elongated (maximum width excluding basal strut / total length = 0.16), subcylindrical; basal hood comparatively small, elongated oval, not notched posteriorly; ventral valve subtriangular, its apex acute, with a pair of lateral groups of 2–3 setae; no hinge sclerite; internal sac apparently smooth, but showing in fact over almost all its surface thin, slender and irregularly arranged hyaline tubercles (well visible in phase contrast); distally the internal sac is narrowed into a spiny constriction of the already described type; apical bulb lined with very thin backward needles, and a few trichoid sensilla. Basal strut moderately narrow, without dorsal keel, lateral lobes cleft to about 85% their length, pubescent; apex of parameres unmodified, with 10 setae (Fig. 8).

Female. Length (pronotum to apex of last visible tergite): 2.3–3.0 mm; width: 1.3–1.8 mm. Body color more contrasted than in male, with disc of last visible tergite black (almost entirely in some paratypes).

Differential diagnosis. The new species is closely related with B. eminingensis Delobel, 2015 (DELOBEL et al. 2015), but the median lobe is slightly thinner than in the latter species; the arrangement of spines in the distal area of the internal sac is also different, in particular the apical bulb is completely lined with minute spines, whereas it is almost completely smooth in B. eminingensis . It differs from B. nongoniermai Delobel, 2007 , a species with similar median lobe ( DELOBEL 2007), in the presence of hyaline tubercles that are densely packed in the anterior part of the internal sac. Lateral lobes are cleft to 60% in B. nongoniermai , to 65% in B. eminingensis , and to 85% in B. subtilis . The new species is also closely related with B. horridus Delobel & Le Ru, 2015 ; in both species the major part of the median lobe is lined with hyaline tubercles, but these are thick, wide and regularly arranged, like the bricks of a wall in B. horridus (very thin, narrow and irregularly arranged in B. subtilis ); the presence of crenulated villi in the distal part of the internal sac of B. horridus is another highly distinctive character. In B. horridus , the vestiture of the lower part of the body and pronotum sides is white, its antennae are testaceous, with sometimes segments VIII–X darkened, not black as in B. subtilis .

The four species mentioned above are members of the B. albosparsus species group. They share almost identical habitus, with strong individual variations, so the identification of males is particularly challenging and in single females almost impossible if based solely on morphology.

Etymology. The specific epithet (masculine adjective) is a Latin word for ‘subtle, tricky’; it refers to the slight morphological differences with B. eminingensis .

Host plants. Unknown.

Distribution. Kenya (Taita-Taveta County), Republic of South Africa (Mpumalanga Province).