Metallactus bivitticollis ( Jacoby, 1907 )

Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4657 (2), pp. 201-245 : 215-216

Metallactus bivitticollis ( Jacoby, 1907)

( Figs 5 ; 22 )

Cryptocephalus bivitticollis Jacoby, 1907: 838 ; Clavareau, 1913: 136 (catalogue); Blackwelder, 1946: 644 (catalogue); Bachmann & Cabrera, 2010: 60 (annotated checklist).

Metallactus bivitticollis Agrain et al., 2017: 59 (annotated checklist).

Type. Jacoby did not mention the number of specimens under study, but he reported his personal collection as the only type depository. At present, a single syntype is housed in the collection of BMNH. The type designation was made as follows, in order to stabilize the epithet. LECTOTYPE (by present designation): ♂, glued, aedeagus and de- tached abdomen glued on the same card bearing the specimen // “Rep. Argent. Prov. B. Aires” [white label, handwritten] // “Jacoby Coll. 1909-28 a.” [white label, printed] // “Cryptoceph. bivitticollis Type Jac.” [blue label, handwritten] // “Type H. T.” [rounded white and red label, printed] // “This is Griburius / Metallactus not Cryptocephalus Chamorro 2010 ” [white label, handwritten] // “ Metallactus bivitticollis ( Jacoby, 1907) LECTOTYPUS D. Sassi des.” [red label, printed] // ( BMNH). A second potential syntype is housed in the Museo Argentino de Ciencias Naturales, Buenos Aires (Bachmann e Cabrera, 2010). It is labelled as follows: “Rep. Argentina Prov. Buenos Aires I.1895 C. Bruch” [printed, date handwritten] // “Cotypus” [pale green label, printed] // “ Cryptocephalus bivitticollis Jac. ” [red frame, handwritten by Bruch]. However, it was not possible to examine this second specimen.

Type locality. “ Buenos Aires ” ( Argentina).

Further material examined. ARGENTINA: Cordoba Dep. Calamuchita I.1971 (1♀, DSPC) .

Distribution. Argentina.

Diagnosis. A Metallactus of medium size. It belongs to the subgroup characterized by longitudinal elytral design of alternately lighter and darker stripes. M. viator differs in more broadly rounded elytral sides and in antennae remarkably shorter. All examined specimens of M. praetorius , M. chamorroi and M. agonista have color pattern of pronotum and head partly reddish, which is not the case of M. bivitticollis , where dark tints are decidedly black. M. pollinctor and M. hamifer differ in ventral parts and legs completely or almost completely black and in the quite different pronotal colour pattern.

Description of male. Habitus in Fig. 5 a–b (LT). BL = 4.7 mm, BW = 2.6 mm, PL = 1.7 mm, PW = 2.3 mm. Interocular distance 12.8% of BL.

Vertex black. Frons yellow with transverse black patch on its lower part, such black patch almost obliterated in lectotype. Clypeal region yellow as well to vaguely darkened (i.e. almost rusty). Labrum yellow. Vertex quite lustrous, bare, almost impunctate. Frontoclypeal area with sparse pale setae and quite coarse punctation, mainly on its upper part and along internal rim of eyes. Mid-cranial suture short, well impressed. First five antennomeres partly yellowish, sublucid, the subsequent ones totally darkened, dull, more flattened and more diffusedly setose.

Pronotum yellow with two longitudinal black stripes extending from anterior margin to posterior one. Rather lengthened, subcylindrical. Lateral margins thin, almost not visible from above, regularly curved with maximum width just behind middle. Posterolateral impressions obliterated. Surface evenly convex, moderately shiny with scattered well impressed punctation, sparser in center of disc.

Scutellum blackish, sharply truncated at apex, distinctly raised, finely setose and minutely punctured.

Elytron surface yellow with two longitudinal black stripes, extending from basal margin to apical clivus, slightly tapered on their posterior ending. Elytral inner stripe in continuity with prosternal one; basal ending of outer stripe covering humerous. Suture narrowly black. Elytral outline parallel-sided, evenly convex, so that not flattened on disc. Postscutellar area not raised. Humeral callus moderately prominent, impunctate. Surface moderately shiny with fine punctation rather confused in anterior inner part of disc, laterally arranged in almost regular rows, perceptible on elytral apex too. Intervals flat.

Pygidium totally yellow, smooth, covered with sparse shallow punctures and whitish setae.

In lectotype inferior parts of pro- and mesothorax light brown, metaepisterna and metasternum black. Hypomera bare, with well impressed punctures. Meso- and metathorax with finer punctation and scattered setae. Prosternal process coarsely punctured with long setae. Abdominal ventrites yellow, shallowly and sparsely punctured, with sparse setae. First abdominal ventrite can be partly darkened. Legs yellow with femora, tibial apex and tarsi more or less infuscate.

Median depression on fifth abdominal ventrite well delimited, bare, sublucid. Posterior margin of fifth abdominal ventrite distinctly notched. Median lobe of aedeagus ( Fig. 5 c–e) rather squat, cylindrical with blunt, short, triangular apex scarcely separated from the rest of aedeagus. In lateral view apex faintly bent ventrally. Hairy dents scarcely delimited, bearing rather long, curly setae. Aedeagal ventral surface not swollen in lateral view, devoid of particular structures. Endophallus not examined so as not to risk damaging the lectotype.

Female. BL = 5.0 mm, BW = 2.9 mm, PL = 1.6 mm, PW = 2.5 mm. Interocular distance 18.0% of BL. In the single examined specimens hypomera and mesoepimera yellow, rest of inferior part of thorax black.

Fifth abdominal ventrite in females with quite small, deep pit. Bottom of pit bald, semiopaque, impunctate. Vasculum of spermatheca ( Fig. 5g ) compact, scarcely pigmented, with straight, quite short proximal branch, relatively long, gradually tapered distal branch and apex slightly bent downwards. Ampulla strongly pigmented, slightly shifted on dorsal side of vasculum. Duct and sperm gland insertions perceptibly distinct. Duct uniform in size, quite long, slender, coiled, coils rather thick and quite regularly arranged. Distal not coiled portion of duct rather long, slightly winding. Insertion on bursa copulatrix, twisted, swollen, clearly pigmented.

Figures

FIGURES 5–6. M. bivitticollis (5), M. chamorroi (6). 5a–b: habitus; 5c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.8 mm]; 5f: antenna (apical antennomeres missing) [1.8 mm]; 5g: spermatheca [0.5 mm]. 6a–b: habitus; 6c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.8 mm]; 6f: antenna (apical antennomeres missing) [2.0 mm]; 6g: sclerites of endophallus [0.6 mm]; 6h: spermatheca [0.7 mm]. 5a–b: lectotype; 6a–b: holotype. hd: hairy dent; scI–IV: sclerites I–IV of endophallus. Square brackets: length of scale segment.

FIGURES 18–26. Distribution maps for Metallactus hamifer species-group. M. abditus (18); M. agonista (19); M. albivittis (20); M. albopictus (21); M. bivitticollis (22); M. chamorroi (23); M. crassicollis (24); M. dicaprioi (25); M. hamifer (26). Grey squares: localities reported in a generic way.