Metallactus albivittis Suffrian, 1866

Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4657 (2), pp. 201-245 : 211-212

Metallactus albivittis Suffrian, 1866

( Figs 3 ; 20 )

Metallactus albivittis Suffrian, 1866: 284 ; Clavareau, 1913: 92 (catalogue); Blackwelder, 1946: 640 (catalogue).

Type. In the original description, Suffrian did not mention the number of the studied specimens but he reported the name of single collector (Sellow), a single locality (“Allegrette”) and a single type location ( MNHUB), where a single syntype has been tracked down. As the MNHUB catalogue quotes a single specimen forming the type series, this one must be considered the holotype by monotypy (ICZN, Art. 72.4.1.1 and Art. 73.1.2). The label information of the specimen matches the registration data from the old catalogue of the MNHUB (“23960 Metallactus albivittis Suffr. * 1. Allegrette, Sello”). The typification has been made as follows, in order to stabilize the epithet. HOLOTYPE: ♂, glued, aedeagus glued on the same card bearing the specimen, abdomen glued on a separate card // “23960” [white label, printed] // “ albivittis Suffr. * Allegr. Sellow.” [blue label, handwritten] // “Hist.-Coll. ( Coleoptera ) Nr. 23960 Metallactus albivittis Suffr. * Allegrette, Sellow Zool. Mus. Berlin ” [green label, printed] // “ HOLOTYPE Metallactus albivittis Suffrian, 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus albivittis Suffrian, 1866 HOLOTYPUS D. Sassi det.” [red label, printed] // ( MNHUB).

Type locality. Alegrete (Rio Grande do Sul, Brazil) .

Further material examined. 1♀, Brazil, Baly coll. ( BMNH) .

Distribution. Brazil.

Diagnosis. A Metallactus of small-(medium) size. It belongs to the subgroup with elytral pattern of longitudinal stripes alternately dark and light. It can easily be distinguished by its very light color, being the darker tint ochraceous and not blackish or brownish like in the other species of the subgroup (only pronotal sides and humeral calli narrowly infuscate). Only M. sekerkai has a similar hue in dorsal pattern, but it shows a single large elytral longitudinal reddish stripe (two, slenderer, in M. albivittis ). Besides, pronotum is remarkably more transverse, the overall outline is stockier and median lobe of aedeagus is very differently shaped.

Description of male. Habitus in Fig. 3 a–b (HT). BL = 4.5 mm, BW = 2.5 mm, PL = 1.6 mm, PW = 2.2 mm. Interocular distance 13.3% of BL.

Head light brown, slightly darker on vertex and along median line of frons. Labrum yellow. Vertex quite dull, almost bare, rather regularly punctured. Frontoclypeal area with short, sparse, pale setae, mostly on lower part of clypeus, with quite robust and regularly distributed punctation. Mid-cranial suture long, extending from upper part of vertex to frontoclypeal suture, well impressed so that surrounding surface distinctly swollen. First five antennomeres brownish, sublucid, the subsequent ones similarly coloured, dull, more flattened and more diffusedly setose.

Pronotum light brown with a narrow median longitudinal yellow stripe reaching both anterior and posterior margins, slightly broadened backwards. A lateral yellow band along each side, not reaching margins that are narrowly blackish. Pronotal shape narrowly elliptical. Lateral margins thin, gently and regularly curved with maximum width at half length. Posterolateral impressions very faintly impressed, barely visible. Surface evenly convex, rather shiny with well impressed, regularly distributed punctation.

Scutellum light brown, dull, slightly raised, finely setose and very minutely punctured. Apex truncated in a straight line.

Elytron surface light brown with two longitudinal yellow stripes extending from anterior margin to apex. First stripe, narrower, along suture; second stripe, in continuity with pronotal lateral yellow patch, running just along the inner side of humeral callus. Longitudinal yellow stripes coalesce at apex of elytra. Humeral callus blackish. Epipleuron yellow. Elytral outline parallel-sided and very weakly flattened on disc. Postscutellar area not raised. Humeral callus moderately prominent, impunctate. Surface rather shiny with distinctly impressed punctures arranged in almost regular rows, visible up to elytral clivus. Intervals flat to slightly raised.

Pygidium yellow, smooth, covered with dense, shallow punctures and short whitish setae.

Inferior parts of thorax light brown. Hypomera almost bare, covered with rather coarse, sparse punctation, mesoepimera and mesoepisterna almost bare with shallow punctures. Metaepisterna and metasternum with quite coarse dense punctation and sparse setae. Prosternal process coarsely punctured with long setae and raised short triangular apex.Abdominal ventrites completely yellow shallowly and sparsely punctured, with sparse setae. Legs yellow with tibial apexes and tarsi moderately infuscate.

Median depression on fifth abdominal ventrite quite deep and relatively large. Posterior margin of fifth abdominal ventrite weakly notched. Median lobe of aedeagus ( Fig. 3 c–e) cylindrical, perceptibly expanded towards apex in ventral view. Apex scarcely separated from the rest of aedeagus, short. In lateral view apex faintly bent ventrally. Hairy dents well impressed, apparent, bordered with a thickened and salient outer rim, bearing scarce, tiny setae. Aedeagal ventral surface slightly swollen and humped in lateral view. Endophallus not examined so as not to jeopardize the aedeagus of the unique male available specimen.

Female. BL = 4.8 mm, BW = 2.9 mm, PL = 1.8 mm, PW = 2.5 mm. Interocular distance 16.7% of BL. In the only available female antennae are frankly black. Besides, external elytral yellow stripe is narrowly bordered of black from the humeral callus up to elytral apex.

Fifth abdominal ventrite in females with quite large and shallow pit. Bottom of pit bald, matt, impunctate. Vasculum of spermatheca ( Fig. 3g ) slender, scarcely pigmented, with straight proximal branch, long distal branch abruptly tapered in pointed apex. Ampulla strongly pigmented, slightly shifted on dorsal side of vasculum. Duct insertion and sperm gland insertion very close to each other but perceptibly distinct. Duct uniform in size, slender, coiled with coils rather loose and somewhat irregularly arranged. Distal not coiled portion of duct very long, winding. Insertion on bursa copulatrix large, swollen, clearly pigmented.

Figures

FIGURES 3–4. M. albivittis (3), M. albopictus (4). 3a–b: habitus; 3c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 3f: antenna [2.1 mm]; 3g: spermatheca [0.5 mm]. 4a–b: habitus; 4c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 4f: sclerite I and dorsal spicule of endophallus [0.5 mm]; 4g sclerites II–III–IV of endophallus [0.5 mm]; 4h: spermatheca [0.5 mm]; 4k: antenna [1.5 mm]. 3a–b: holotype; 4a–b: lectotype. hd: hairy dent; scI–IV: sclerites I–IV of endophallus; ds: dorsal spicule. 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.