Metallactus tarsalis Suffrian, 1866

Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4657 (2), pp. 201-245 : 238-239

Metallactus tarsalis Suffrian, 1866

( Figs 16 ; 33 )

Metallactus tarsalis Suffrian, 1866: 280 ; Clavareau, 1913: 94 (catalogue); Blackwelder, 1946: 641 (catalogue).

Types. Suffrian did not mention the number of specimens under study but he reported the name of single collector (Sellow), a single locality (“Porto Allegre”) and a single type location (MNHUB), where three syntypes have been tracked down. The label information matches the registration data from the old catalogue of the MNHUB (“23989 Metallactus tarsalis Suffr. * 3. Porto Allegre, Sello”). The typification has been made as follows, in order to stabilize the epithet. LECTOTYPE (by present designation): ♂, glued, aedeagus glued on the same card bearing the specimen, abdomen and sclerites of endophallus glued on a separate card // “23989” [white label, printed] // “ tarsalis Suffr. * Porto All. Sellow” [blue label, handwritten] // “Hist.-Coll. ( Coleoptera ) Nr. 23989 Metallactus tarsalis Suffr. * Brasil., Sellow Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus tarsalis, 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus tarsalis Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (MN- HUB). PARALECTOTYPES: 1♂ 1♀ // “Hist.-Coll. ( Coleoptera ) Nr. 23989 Metallactus tarsalis Suffr. * Brasil., Sellow Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus tarsalis, 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus tarsalis Suffrian, 1866 PARALECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB).

Type locality. Porto Alegre (Rio Grande do Sul, Brazil) .

Distribution. Brazil.

Diagnosis. A Metallactus of medium size. The dorsal color pattern is quite distinctive in the available specimens, but some remnants of possible longitudinal elytral black lines in lectotype suggests closeness to M. praetorius and M. chamorroi on the basis of the particular pronotal color. However, in M. praetorius the punctation of the forehead is somehow different, being weaker and more regurlarly arranged. Besides interocular distance is much larger in the latter species. In the comparison between males of the two species, the lateral margin of the pronotum is more clearly curved in the posterior tract in M. praetorius . Differences in the forehead punctation and in the in- terocular distance are less apparent in females, but the antennae are completely black in M. praetorius , while the first articles are yellow in M. tarsalis . Furthermore, in the present species anterior part of the hypomera is intensely black whereas it is reddish in M. praetorius (but the only male specimen of M. praetorius has a small black spot on the hypomera!). M. chamorroi is distinguishable above all for the stronger and closer pronotal punctures, clearly discernible in the middle of disc as well, and for the shape of the median lobe.

Description of male. Habitus in Fig. 16 a–b (PLT). BL = 4.6-4.8 mm, BW = 2.7 mm, PL = 1.6 mm, PW = 2.4 mm. Interocular distance 12.5-13.0% of BL.

Head reddish brown, slightly darker on upper part of vertex, mid-cranial suture and above antennal sockets. Labrum yellowish. Vertex scarcely shiny, almost bare. Frontoclypeal area with sparse, rather long, pale setae. Head surface covered with sparse, quite coarse punctures. Mid-cranial suture quite long, well impressed, so that surrounding surface looks fairly swollen. First five antennomeres partly yellowish, sublucid, the subsequent ones totally darkened, dull, more flattened and more diffusedly setose.

Pronotum yellow with two longitudinal stripes extending from anterior margin to posterior one, slightly diverging backwards. Those stripes are anteriorly black and posteriorly red, with black-red border obliquely arranged so that black patch is prevalently on inner-anterior section and red color on outer-posterior one. Pronotal shape troncoconical, scarcely transverse. Lateral margins thin, visible from above only along their rear section, regularly curved with maximum width just behind half length. Posterolateral impressions obliterated so that posterior margin not thickened behind it. Surface regularly convex, moderately shiny with rather coarse punctation almost obliterated on central part of disc.

Scutellum ochreous, sometimes with apical margin narrowly black, scarcely shining, distinctly raised, finely setose and minutely punctured. Apex truncated in a straight line.

Elytron surface yellow with suture narrowly ochreous to brownish. Humeral callus slightly darkened. In lectotype some remnant of possible longitudinal black stripe just before apical clivus. Elytral outline parallel-sided and very weakly flattened on disc. Postscutellar area not raised. Humeral callus moderately prominent, impunctate. Surface moderately shiny with quite well impressed punctures, rather closely and irregularly arranged, hints of almost regular rows only on apical clivus and sides. Intervals flat.

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

Inferior parts of thorax black with rear section of hypomera, mesoepimera and mesoepisterna ochreous. In lectotype metaepimera and metaepisterna partly ochreous as well. Hypomera, mesoepimera and mesoepisterna almost bare with scarce quite deep punctures. Metaepisterna and metasternum with quite thick, shallow punctation and sparse setae. Prosternal process coarsely punctured with long setae and raised short triangular apex. Abdominal ventrites yellow, only first visible one narrowly bordered of black along its anterior margin, shallowly and sparsely punctured, with sparse setae. Legs ochreous with infuscate tarsi.

Median depression on fifth abdominal ventrite quite large and shallow with rather shiny bottom. Posterior margin of fifth abdominal ventrite weakly notched. Median lobe of aedeagus ( Fig. 16 c–e) cylindrical with apex scarcely separated from the rest of aedeagus. In lateral view apex weakly bent ventrally. Hairy dents very poorly impressed, faintly delimited, bearing rather long and straight setae. Aedeagal ventral surface barely swollen in lateral view, devoid of particular structures. Endophallus ( Fig. 16f ) with sclerite I strongly developed and pigmented, denticle apparent, forwardly directed, not sticking out laterally. Dorsal spicule very close to (basically fused with) denticle of sclerite I, small, ribbon-like. Sclerite II rather short, squat, distinctly bent at base and gradually tapered towards apex.Arch of sclerite III slender, moderately raised.Apex of sclerite III straight and pointed, weakly expanded on its proximal half. Branches of sclerite IV shorter than sclerite III in the folded-up structure, almost straight with blunt, strongly asymmetrical, microdenticulate apex and surface distinctly rugose.

Female. BL = 5.4 mm, BW = 3.3 mm, PL = 1.8 mm, PW = 2.7 mm. Interocular distance 16.7% of BL.

Fifth abdominal ventrite in females with quite large and deep pit. Bottom of pit bald, matt, impunctate. Spermatheca not examined.

Figures

FIGURES 16–17. M. tarsalis (16), M. viator (17). 16a–b: habitus; 16c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.6 mm]; 16f: sclerites of endophallus [0.4 mm]; 16g: antenna [2.2 mm]. 17a–b: habitus; 17c: spermatheca [0.6 mm]; 17d: antenna [1.8 mm]. 16a–b: paralectotype; 17a–b: holotype. hd: hairy dent; scI–IV: sclerites I–IV of endophallus; ds: dorsal spicule. Square brackets: length of scale segment.

FIGURES 27–34. Distribution maps for Metallactus hamifer species-group. M. luniger (27); M. madefactus (28); M. octoguttatus (29); M. pollinctor (30); M. praetorius (31); M. sekerkai (32); M. tarsalis (33); M. viator (34). Grey squares: localities reported in a generic way.