Metallactus argentinensis Jacoby 1907
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2020
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus argentinensis

description: Metallactus argentinensis Jacoby, 1907
(Figs 2; 4b; 6)
Metallactus argentinensis Jacoby, 1907: 850; Clavareau, 1913: 92 (catalogue); Blackwelder, 1946: 641 (catalogue); Agrain et al., 2017: 59 (annotated checklist).
Material examined. Types. Jacoby did not mention the number of specimens studied. However, three syntypes, all males, are housed in BMNH. One of these is hereby designated lectotype, to fix the identity of the species. LECTO-TYPE: ♂, body and aedeagus glued on the same card, abdomen glued on a separate card, // “ Argent. Cordoba ” [white label, handwritten] // “ Jacoby Coll. 1909-28a.” [white label, printed] // “ Syntype ” [round white label with blue margin, printed] // “ Metallactus argentinensis Jacoby, 1907 LECTOTYPUS D. Sassi des.” [red label, printed] // (BMNH). PARALECTOTYPES: ♂, body and aedeagus glued on the same card, abdomen glued on a separate card, // “ Argent. Cordoba ” [white label, handwritten] // “ Jacoby Coll. 1909-28a.” [white label, printed] // “ Metallactus argentinensis Jac. Type ” [blue label, handwritten] // “ Type H. T. ” [round white label with red margin, printed]; ♂, body, aedeagus and detached abdomen glued on the same card, // “ Cordoba ” [blue label, printed] // “ Argent. Cordoba ” [white label, handwritten] // “ Jacoby Coll. 1909-28a.” [white label, printed] // “ Syntype ” [round white label with blue margin, printed]. Both paralectotypes bear a red, printed label: // “ Metallactus argentinensis Jacoby, 1907 PARALECTOTYPUS D. Sassi det.” [red label, printed] // (BMNH).
Type locality. Cordoba (Argentina).
Additional material examined. (93 specimens examined altogether, 14 males and 7 females dissected to check genitalia). ARGENTINA: Cordoba Anizacate H. H. Maristas F. Monros collection 1959 (4, NMNH); Rosario bei Cordoba coll. H. Stempelmann (1, DSPC); Cordoba La Cumbre 4.II.2015 Agnoli Leg. (4, DSPC); Prov. de Santiago del Estero Averias Rio Salado E. Wagner lg. (2, MNHN); Entre Rios D. Harold [18]77 (1, MSNG); Catamarca La Merced (1, NMV); La Roja Villa Castelli y Chilecito IV.1954 leg. H. Förster (4, ZSM); Cordoba dept. Calamuchita Yacanto III.1975 leg. M. Viana (1, NHMP); Cordoba dept. Calamuchita San Ignacio II.1972 leg. M Viana (1, NHMP); Cordoba Capilla d. Monte coll. Prf. Hosseus (2, ZSM); Chaco de Santiago del Estero Rio Salado (7, NHMP); Chaco de Santiago del Estero Rio Dulce (1, NHMP); Chaco de Santiago del Estero Averias, E. R. Wagner 1914 (2, MNHN); Chaco de Santiago del Estero Bords du Rio Salado Averias, E. R. Wagner 1909 (2, MNHN); Chaco de Santiago del Estero Bords du Rio Salado env. d’Icano Mistol Paso E. R. Wagner 1914 and 1918 (5, MNHN). BRAZIL: ”Brasilien Alte Sammlung” (1, NHMB). PARAGUAY: San Bernardino K. Fiebrig (4, NMNH); Dept. Amambay Parq. Nac. Cerro Corà 24.II.1981 (1, NMNH); “ Paraguay ” (2, MNHUB); “ Paraguay ” leg. Fiebrig (14, MNHUB); San Bernardino XI.1898 G. Boggiani (2, MSNG); San Bernardino W. Eisenlohr (2, MNHUB); Capiata II. 1995 (2, MSNM); Dept. Pte Ayes Villa Ayes V.1992 (1, DSPC); Paraguan prov. La Colmena 21.II.2008 J. Halada leg. (1, NHMP); Asuncion Revoil 1891 (2, MNHN); Asuncion Anisits IX–X.[1]904 (1, HNHMB); Asuncion Villa Morra Vezény (1, HNHMB); Sapucay W. T. Foster coll. (1, NMNH); Concepción prov. 120 km NEE Concepción 2.II.2008 J. Halada leg. (1, NHMP); Paraguan prov. 20 km W La Colmena 19.II.2008 J. Halada leg. (1, NHMP); Paraguary dept. Ybycui in Ybycui Nat. Park 12-24.IV.1980 P. J. Spangler (1, NMNH); Paraguary 7.2 km N Paraguary 18. V.1986 R. E. Woodruff (3, FSCA); Paraguari Naranjo II. 1995 and X.1995 (9, MSNM); San Luis Reimoser (5, NMV).
Distribution. Argentina, Brazil, Paraguay. This species is newly recorded from Brazil and Paraguay.
Diagnosis. Metallactus argentinensis differs from M. generosus in narrower pronotal black pattern, which is usually split into two longitudinal stripes, sometimes coalescing anterad but never reaching lateral margins. Metallactus generosus is also different in the remarkably expanded apex of the sclerite IV branches of endophallus. Metallactus nigroplagiatus is very similar in dorsal colour pattern, but elytral lateral margins are marked with an unbrocken yellow stripe extended from base to apex, while such stripe is split into an anterior patch and an apical spot in M. argentinensis. Metallactus nigroplagiatus also differs in the expanded apical section of the endophallic sclerite IV branches. In the examined specimens, the notch on the posterior margin of fifth abdominal sternite in males is somehow deeper in M. argentinensis than in the other species in study.
Description of male. Habitus in Fig 2 a–b (LT). BL = 4.8–5.2 mm, BW = 2.6–3.0 mm, PL = 1.6–1.9 mm, PW = 2.3–2.7 mm. Interocular distance 8.9–10.0 % of BL.
Head black with a pentagonal yellow spot (Fig. 4b) extending from upper part of frons to basal half of vertex. Labrum yellowish. Surface of frons dull, punctuation barely evident, whitish setosity long, dense just below the yellow spot, almost regularly distributed on clypeus, ocular canthus and rim of labrum. Vertex almost impunctate, glabrous. Mid-cranial suture, when present, short, visible only on yellow patch, sometimes obliterated. Ocular lines narrow, well impressed, strictly adhering to ocular rim. Ocular canthus with rather impressed punctures. Antennae (Fig. 2h) with first five antennomeres sublucid, yellowish, 3–5 rod-shaped, 6–11 totally darkened, dull, quite similar in shape to the basal ones but more diffusedly setose.
Pronotum yellow with two black spots ranging from anterior margin, quite variable in shape and dimension: often slightly wavy, oblique, generally extending posteriorly beyond midline, sometimes reaching posterior margin or coalescing along their anterior section, rarely reduced to small rounded spots. In all examined specimens such black patches never reaching lateral margins which are therefore yellow along their whole length. Pronotal shape shortly tronco-conical, regularly convex. Lateral margins narrow, barely visible from above, regularly curved with maximum width just behind half of length. Posterolateral impression missing, so that posterior margin not swollen toward sides. Surface moderately lustrous with scattered, rather strongly impressed punctation, denser on sides, sparser on disk.
Scutellum completely black, moderately raised, subquadrate with posterior margin truncated in a straight line. Surface matt, with scattered setosity.
Elytron black with one anterolateral subrectangular yellow patch, ranging from anterior margin and utterly covering epipleuron, sometimes extended beyond midline, in other cases markedly reduced; a second yellow spot on apex, extended to part of apical clivus. Elytral outline parallel-sided, rather squat, elytral disc weakly flattened on its posterior part. Lateral margins simultaneously visible from above up to humeral calli. Postscutellar area not raised. Humeral callus prominent, impunctate. Elytral surface dull with shallow, rather dense punctation, quite irregularly arranged in particular on basal half. Intervals flat. Epipleuron smooth, impunctate, with shallowly convex surface.
Pygidium totally black, smooth, covered by sparse rather shallow punctures and pale setae.
Inferior parts of thorax completely black, with sparse and scarcely apparent punctation and rather dense setosity. Only hypomera almost glabrous, shiny, with well impressed, sparse punctures.
Inferior parts of thorax completely black (with exception of outer yellow hypomera), with sparse and scarcely apparent punctation and rather dense setosity. Only hypomera almost glabrous, shiny, with well impressed, sparse punctures.
Prosternal process longitudinally grooved, covered with long setae and raised blunt, short triangular apex. Abdominal ventrites completely yellow to brownish, shallowly and sparsely punctured, with sparse setae. Legs totally black.
Fifth abdominal ventrite with a small, rather impressed, finely punctured, glabrous, median depression and moderately notched posterior margin. Median lobe of aedeagus (Fig. 2 c–e) cylindrical with smooth surface and apex triangular, short, quite blunt, usually feebly but perceptibly bent ventrally in lateral view. Setose depressions shallow, barely delimited, with scattered setae. In ventral view median lobe rather convex, with sometimes a faintly raised longitudinal carena along its basal half. Ventral profile fairly swollen in lateral view. Endophallus (Fig. 2f) with sclerite I well developed and pigmented, denticle apparent, blunt, scarcely directed upwards. Dorsal spicule well developed, sometimes distinctly pigmented, with pointed apex. Sclerite II well developed, slender, almost regularly curved. Arch of sclerite III slender, rather short. Apex of sclerite III slightly bent downwards, slender and rather lengthened, evenly thickened. Branches of sclerite IV about as high as sclerite III in the folded-up structure, rather stocky, regularly bent basally, moderately broadened distally, surface covered with tiny, obliquely arranged wrinkles, edge minutely serrate.
Female. BL = 4.8–5.4 mm, BW = 2.9–3.3 mm, PL = 1.6–1.7 mm, PW = 2.5–2.8 mm. Interocular distance 14.6–14.8 % of BL.
Females remarkably differ in pronotum more extensively black, often with a single black patch covering great part of surface and extending to anterior section of lateral margins. This latter colour pattern can make it difficult, or even impossible, to distinguish female specimens from the ones of M. generosus.
Fifth abdominal ventrite in females with quite large, rounded, well impressed pit. Bottom of pit glabrous, matt, impunctate but covered by tiny wrinkles. Vasculum of spermatheca (Fig. 2g) scarcely pigmented with straight proximal lobe mildly swollen at base, short distal lobe and apex pointed. Ampulla slightly pigmented, barely shifted on dorsal side of vasculum. Duct insertion and sperm gland insertion perceptibly distinct. Duct uniform in size, slender, coiled with coils rather loose and somewhat irregularly arranged. Not coiled portion of duct near bursa copulatrix rather long, slightly winding. Insertion on bursa copulatrix lengthened, perceptibly bent and slightly swollen, clearly pigmented.
description: Published as part of Sassi, Davide, 2020, Revision of the Metallactus generosus species-group with a preliminary evaluation of the effectiveness of the endophallus morphology in distinguishing critical sibling species (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 148-162 in Zootaxa 4877 (1) on pages 155-157, DOI: 10.11646/zootaxa.4877.1.6, http://zenodo.org/record/4423973