Metallactus abditus, Sassi, 2019

Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4657 (2), pp. 201-245 : 207-208

Metallactus abditus sp. nov.

( Figs 1 ; 18 )

Type. HOLOTYPE: ♂, glued, abdomen and aedeagus glued on the same card bearing the specimen // “ Parag: Central Asunción Jan. 15, 1983 Coll. E.G. Riley ” [white label, printed] // “ Metallactus abditus sp. nov . HOLOTYPUS D. Sassi des.” [red label, printed] // ( TAMU). The holotype is the only specimen known so far .

Etymology. Latin past participe abditus meaning “hidden”.

Type locality. Asunción ( Paraguay).

Distribution. Paraguay.

Diagnosis. A Metallactus of small size belonging to a subgroup of four species ( M. albopictus , M. octoguttatus , M. madefactus and M. abditus ) distinguished by a pronotal V-shaped yellow spot just in front of scutellum. The present species can be distinguished in stouter body and, above all, in distinctly finer dorsal punctation. The pronotal lateral spot tends to be L-shaped in M. albopictus and M. madefactus , while in M. abditus and M. octoguttatus it is C-shaped, being more salient along posterior margin. Besides, the median elytral spot tends to be more transverse in M. albopictus , sometimes reaching lateral margin, while in M. abditus and M. octoguttatus this spot is basically rounded. Apical spot is differently shaped in the closer species, being split in two parts in M. octoguttatus and in M. madefactus . Finally, M. abditus is easily distinguished from M. albopictus and M. octoguttatus on the basis of the aedeagal shape.

Description of male. Habitus in Fig. 1 a–b (HT). BL = 4.3 mm, BW = 2.6 mm, PL = 1.5 mm, PW = 2.4 mm. Interocular distance 14.0% of BL.

Head black, with a rough W-shaped yellow spot on lower part of vertex. Labrum blackish with yellow border. Vertex quite dull, bare, with few punctures scattered on yellow spot. Frontoclypeal area with sparse pale setae and quite coarse punctation. Mid-cranial suture short, well impressed so that surrounding surface fairly swollen. Antennae black, with antennomeres 1–4 partly brownish.

Pronotum black with lateral margin and outer part of anterior and posterior margins covered with a single Cshaped spot; a median V-shaped yellow spot close to posterior margin just in front to scutellum; a smaller elliptical median one, yellow as well, close to anterior margin. Pronotal shape short-elliptical with lateral margins thin, barely visible from above, regularly curved so that maximum witdh roughly in the middle. Posterolateral impressions obliterated. Surface moderately lustrous with scattered, feebly impressed punctation, slightly sparser and shallower on disc.

Scutellum completely black, distinctly raised, sub-squared with truncated apex, almost bald and impunctate with tiny and sparse micropunctation.

Elytron black with yellow pattern as follows. Two rounded spots along the suture, first one beside scutellum, the second at middle; a third hooked spot on apical clivus, concave toward median line, leaving a very thin black rim at apex and suture. A further curved yellow spot surrounding humerous and extended on outer part of anterior margin and epipleuron. Rather short, elytral outline parallel-sided and very weakly flattened on disc. Postscutellar area faintly raised. Humeral callus scarcely prominent, impunctate. Surface rather lustrous with punctation scarcely impressed, arranged in almost regular rows, clearly reduced and shallower on apical clivus. Intervals flat. Epipleural surface slightly convex, smooth, devoid of punctation.

Pygidium yellow with a black stripe along proximal margin and a rounded black one on apex, with surface smooth, covered with sparse shallow punctures and whitish setae. Two transverse pits close to each lateral margin of pygidium, roughly at half of length.

Inferior parts of thorax completely black. Prothorax (prosternal process and hypomera) rather coarsely punctured; meso and metathorax rather shallowly punctured on sides, with sparse, whitish setae. Abdominal ventrites regularly and shallowly punctured, rather densely covered with whitish setae, with large yellow border. Legs totally black.

Fifth abdominal ventrite with a median, brownish, quite impressed, rounded depression, smooth, glabrous and impunctate at center, and posterior margin fairly notched. Median lobe of aedeagus ( Fig. 1 c–e) with sides slightly concave in ventral view, with blunt, rather short apex scarcely separated from the rest of aedeagus, slightly bent downwards in lateral view. Hairy dents shallow, very poorly delimited, bearing quite long, straight and rather close setae. Ventral profile markedly swollen in lateral view.

Endophallus not examined so as not to jeopardize the aedeagus of the unique available specimen.

Female unknown.

Figures

FIGURES 1–2. M. abditus (1), M. agonista (2). 1a–b: habitus; 1c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.9 mm]; 1f: antenna [1.5 mm]. 2a–b: habitus; 2c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.8 mm]; 2f: sclerite I–II of endophallus (on the left: sclerite I in dorsal view) [0.7 mm]; 2g: sclerites III–IV of endophallus [0.4 mm]; 2h: spermatheca [0.4 mm]; 2k: antenna [1.4 mm]. 1a–b: holotype; 2a–b: lectotype. hd: hairy dent; scI–IV: sclerites I–IV of endophallus; rp: rounded projection externally delimiting hairy dent. 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.