Metallactus cultus D. Sassi 2022, n. comb.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus cultus

description: Metallactus cultus (Suffrian, 1866) n. comb.
(Figs 1; 11)
Scolochrus cultus Suffrian, 1866: 233.
Griburius cultus Burmeister, 1877: 65 (annotated checklist); Clavareau, 1913: 89 (catalogue); Blackwelder, 1946: 639 (catalogue); Agrain et al., 2017: 57 (annotated checklist).
Types. Suffrian (1866) did not mention the number of specimens (only females) under study, but he reported Puerto Alegre (leg. Sellow in MNHUB), South Brazil (leg. Beske in coll. Schaum); Paraguay (leg. Vogt in coll. v. Heyden) and Buenos Aires (coll. Haag) as the collection localities. Four syntypes were located in MNHUB and two (coll. V. Heyden and coll. Haag) were found in SDEI.A lectotype is designated as follow: lectotype (by present designation): ♀, pinned, //”biplagiatus N. Porto All. Sell.” [blue label, handwritten] // “24033” [white label, printed] // “cultus (v. Heyd.) Suffr.*” [white label, handwritten] // “Hist.-Coll. (Coleoptera) Nr. 24033 Scolochrus cultus Suffrian * Porto Allegre, Sello. Zool. Mus. Berlin” [green label, printed] // “ SYNTYPUS Griburius cultus (Suffrian, 1866) labelled by MNHUB 2013” [red label, printed] // “ Griburius cultus (Suffrian, 1866) (Scolochrus cultus) LECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus cultus (Suffrian, 1866) D. Sassi det. 2021” [white label, printed] // (MNHUB). Paralectotypes: 3♀, pinned, // “Hist.-Coll. (Coleoptera) Nr. 24033 Scolochrus cultus Suffrian * Porto Allegre, Sello. Zool. Mus. Berlin” [green label, printed] // “ SYNTYPUS Griburius cultus (Suffrian, 1866) labelled by MNHUB 2013” [red label, printed]; 1♀, pinned, // “70” [white label, handwritten] // “coll. V. Heyden” [white label, printed] // “ Scolochrus cultus Heyd. Suffr. orig. Parag. Voegt.” [white label, handwritten] // “DEI Müncheberg Col—14368” [green label, handwritten] // (SDEI); 1♀, pinned, // “Buen. Ayr Kraatz” [white label, handwritten] // “coll. Haag” [white label, printed] // “ cultus Suffr. ” [white label, handwritten] // “DEI Müncheberg Col—14369” [green label, handwritten] // (SDEI). All paratypes labelled: “ Griburius cultus (Suffrian, 1866) (Scolochrus cultus) PARALECTOTYPES D. Sassi des.” [red label, printed] // “ Metallactus cultus (Suffrian, 1866) D. Sassi det. 2021” [white label, printed] // (MNHUB). The information on the original old labels (on the lectotype only) matches the registration data from the old catalogue of the MNHUB (“24033 [Scolochrus] cultus Suffr. * 4. Porto Allegre, Sello”).
Type locality. Puerto Alegre (Rio Grande do Sul, Brazil).
Additional material examined. (20 specimens examined altogether). ARGENTINA: Cordoba Fanti Sierra de Cordoba 11.I.1966 Mahunka leg. (1, HNHMB); Misiones San Ignacio Villa Lutecia E. R. Wagner VI-IX.1910 (2, MNHN); Entre Rios Liebig XII.1987 and XII.1989 and XI.1990 and XII.1991 (5, DSPC); Corrientes 32 km E Ituzaingó 20.I.1989 CW & LB O‘Brien & G. Wibmer (2, BYU); Provincia de Buenos Aires Juan B. Daguerre (1, USNMNH). BRAZIL: Rio Grande do Sul Porto Alegre X-XI 1958 K. E. Hüdepohl (2, NHMB); Minas Geraez Caraça 1.II.1885 E. Gounelle (1, MNHN). PARAGUAY: Capiatá II.1995 (DSPC); Paraguarí Prov. 20 km W La Colmena 19-21.2008 (DSPC); 3 km E Ypacaraí 10.X.1968 (BYU); Sapucay WT Foster coll. (1, USNMNH). URUGUAY: “Uruguay” (1, MNHUB); Colonia Piedra de los Indios ca Ruta 21 Km 184,5 10.XI.2010 and 21.XI.2010 and 13.XI.2012 G. J. Wibmer (4, BYU); Colonia Ruta 21 Piedra de los Indios 9.XI.1992 G. J. Wibmer (1, BYU); Rocha Establecimiento Casablanca Ruta 109 15 Km W Rocha 18.XI.2011 G. J. Wibmer (2, BYU); Rocha, old Ruta 9 near Castillos 15.XI.2011 G. J. Wibmer (1, BYU).
Distribution. Argentina, Brazil, Paraguay, Uruguay (new).
Diagnosis. The species was described as belonging to the genus Scolochrus (now Griburius), but the shape of the male genitalia, the morphology of the pronotal process, the interocular distance and the overall outline clearly suggest a shift to the genus Metallactus. The most common colour pattern in females tends to be rather distinct from those of the other species of the same group due to the subquadrate black marking in the anteromedian part of the pronotum, occasionally divided in two (as in the lectotype), and by the elytral black stripe generally with constant width, or weakly broadened posteriorly, and not reaching the apex. Great variability in the colour pattern makes the determination very uncertain unless males can be examined.
Description of male. BL = 4.0– 4.4 mm, BW = 2.3–2.6 mm, PL = 1.4–1.5 mm, PW = 2.0– 2.3 mm. Interocular distance 6.8–7.5 % of BL.
Head black with yellow spot covering almost all frontoclypeal area. Roughly circular to subtriangular yellow spot in middle of frons. Labrum blackish at times with lighter borders. Vertex coarsely punctured with few scattered whitish setae. Surface of frontoclypeal area dull, punctuation coarse and scattered, evident; setae sparse, recumbent, whitish, longer on lower part of surface. Mid-cranial suture short, well impressed. Ocular lines narrow, strictly adhering to ocular rim seeping into upper part of ocular canthus, whose surface impunctate elsewhere. Ocular canthus with sparse, long, semi-erect setae. Antennae (Fig. 1h) brownish with antennomeres 2-5 lighter, moderately lengthened. Antennomeres 6-11 dull, stouter, and shorter.
Pronotum black, often with yellow lateral margins. Yellow colour on lateral margins at times missing in middle. Sometimes posterior margin narrowly spotted with yellow just in front to scutellum. Pronotal shape roughly elliptical with surface convex, fairly flattened on disc towards base. Lateral margins narrow, regularly curved With maximum width just below midline. Surface moderately shiny with scattered, strongly impressed punctation, denser on sides, sparser on disc. Posterolateral impressions short and weakly impressed to completely obliterated.
Scutellum completely black, moderately raised, trapezoidal with apex truncated in straight line. Surface minutely and sparsely punctured, with scarce, very short setae.
Elytron yellow with one black median longitudinal stripe ranging from anterior margin to beyond the midline, barely reaching the posterior clivus. Suture narrowly black. In some specimens elytral pattern quite different, having surface extensively black with rectangular yellow spot on humeral surface, and second one, rounded, yellow as well, on apical clivus. Epipleuron totally yellow. Elytral outline with sides straight and slightly convergent posteriorly, very weakly flattened on disc. Lateral margins narrow, not simultaneously visible from above along anterior half. Elytral surface moderately shiny with coarse, close punctation, quite irregularly arranged in rows, more apparent on apical half. On lighter area bottom of punctures only slightly darker than interval surface Intervals flat. Postscutellar area very weakly raised. Humeral callus prominent, impunctate. Epipleuron smooth, impunctate, slightly bulging, with slightly convex surface.
Pygidium piceous often with two narrow yellow stripes along sides, matt, covered by sparse coarse punctures and long, appressed, pale setae.
Ventral parts of thorax totally black. Abdominal ventrites blackish, often very narrowly yellow along sides. Hypomera, mesoepimera and mesoepisterna almost bare, shiny, with few scattered punctures. Rest of ventral surface matt, covered with thick, short, regularly distributed setae and shallow punctures. Prosternal process with sides mildly curved at middle, then converging in short, slightly raised, subtriangular apex, surface almost plane onward, more clearly depressed along median section of apical half, with thick, long, semi-erect setae. Legs totally black to blackish with lighter patches on femora and tibia. Anterior coxae often yellowish.
Median depression on fifth abdominal ventrite large, shallow but well delimited from rest of ventrite surface, shiny, bare and impunctate. Ventrite posterior margin raised, largely notched. Median lobe of aedeagus (Fig. 1c–e) laterally compressed with large, flat apex well differentiated from shaft, terminated by short, rounded median denticle. In lateral view apex almost straight. Ventral outline markedly convex but strongly notched in middle. Setose depressions deeply impressed, ear-shaped, separated by deep depression and wide, blunt median carina. Setae short and scattered, mostly visible on the external surface of the wall laterally delimiting setose depressions.
Endophallus (Fig. 1f) with sclerite I basically reduced to pigmented, scarcely sclerotized fold of the membranous apparatus, flattened on top and terminated with large, blunt denticle. Dorsal spicule not detectable. Sclerite II small, strongly pigmented with tiny process upward directed. Sclerite III robust, sickle shaped with short, triangular apex. Branches of sclerite IV shorter than sclerite III in folded-up structure, distinctly arched towards ventral direction with blunt apex and surface smooth.
Female. Habitus in Fig. 1 a-b (PLT). BL = 4.5–4.8 mm, BW = 2.8–2.9 mm, PL = 1.4–1.6 mm, PW = 2.4–2.5 mm. Interocular distance 12.5–13.3 % of BL.
Females differ in chromatic pattern having a pronotum that is often mostly yellow with a subquadrate black spot reaching the anterior margin. For some specimens, including the figured paralectotype (Fig. 1), such a black spot is longitudinally split into two halves. The yellow spot of the frontoclypeal area is smaller and rounded rather than roughly triangular. The head is black with a roughly circular to subtriangular yellow spot just in the middle of the frons. Lighter colour is usually more extensive on the elytron, and the more common pattern (as far as the available information allows to guess) shows the surface mostly yellow with one black median longitudinal stripe extended from anterior margin to beyond midline, barely reaching the posterior clivus. In a single female, the black pattern extends over the entire surface with the exception of one yellow spot on the humeral area and a second one at the apex. This specimen, coming from Entre Rios, also differs in the shape of vasculum, being stouter and less S-shaped. At present it is impossible to attribute any taxonomic significance to these differences.
The fifth abdominal ventrite in females has a quite large and deep pit. The bottom of the pit glabrous, matt, impunctate but covered by tiny wrinkles. The vasculum of the spermatheca (Fig. 1g) is moderately pigmented, in particular over the basal section, S-shaped with twisted, slightly swollen proximal lobe. The distal lobe is rather short, slender, tapered with an acute apex slightly bent downwards. The ampulla is not pigmented, short, sitting just at basal apex of vasculum. The duct and sperm gland insertions are perceptibly distinct. The duct is uniform in size, robust, quite rigid, not really coiled but wavy, meandering beside the vasculum, then almost straight. The insertion on the bursa copulatrix is well pigmented, conical. In a specimen from Capiatá (Paraguay) the distal lobe of the vasculum is remarkably shorter and tapered to an acute apex. The vasculum and ampulla are perceptibly more pigmented. At present it is impossible to give a taxonomic value to this outlier.
description: Published as part of Sassi, Davide, 2022, Revision of the Metallactus taeniatellus species group (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 251-282 in Zootaxa 5125 (3) on pages 255-257, DOI: 10.11646/zootaxa.5125.3.1, http://zenodo.org/record/6443765