Metallactus agonista , Suffrian 1866
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus agonista

description: Metallactus agonista Suffrian, 1866
(Figs 2; 19)
Metallactus agonista Suffrian, 1866: 351; Clavareau, 1913: 92 (catalogue); Blackwelder, 1946: 640 (catalogue).
Types. Suffrian did not mention the number of specimens under study but he reported the name of single collector (Virmond) and a single type location (MNHUB), where two syntypes have been tracked down. The label information and the number of syntypes match the registration data from the old catalogue of the MNHUB (“23958 Metallactus agonista Suffr. * 2. Brasil., Virmnd”). The typification has been made as follows, in order to stabilize the epithet. LECTOTYPE (by present designation): ♀, pinned // “23958” [white label, printed] // “ agonista Suffr. * Brasil. Virm.” [blue label, handwritten] // “Hist.-Coll. (Coleoptera) Nr. 23958 Metallactus agonista Suffr. * Brasil., Virmond Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus agonista, Suffrian 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus agonista Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB). PARALECTOTYPE: 1♀, pinned // “Hist.-Coll. (Coleoptera) Nr. 23958 Metallactus agonista Suffr. * Brasil., Virmond Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus agonista, Suffrian 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus agonista Suffrian, 1866 PARALECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB).
Type locality. “ Brazil ”.
Further material examined. ARGENTINA: Corr [ientes] 42 Km E Ituzaingó 23.I.1989 C. W. & L. W. O’Brien & G. J. Wibmer (1, BYU). BOLIVIA: Santa Cruz Agua Clara 3-4 km NW 12.X.2000 B. K. Dozler (1, FSCA). BRAZIL: São Paulo Parelheiros 8.XII.1975 V. N. Alin (1, FSCA); São Paulo M. Ràz leg (1, NHMP). PARAGUAY: Guairà Col. Independencia 27.II.1950 leg J. Förster (1, ZSM). URUGUAY: Roca Ruta 16 km 1-2 15.XI.2011 G. J. Wibmer (2, BYU).
Distribution. Argentina, Bolivia, Brazil, Paraguay, Uruguay. New for Argentina, Bolivia, Paraguay, Uruguay.
Diagnosis. A Metallactus of small size. It belongs to the subgroup with elytral pattern made up of longitudinal stripes alternately dark and light. Among the species of this subgroup, only M. agonista has pronotum mostly reddish or rusty, with six or four black spots lined up along longitudinal median yellow line. Other species of the subgroup are lacking reddish color on pronotum (M. pollinctor, M. viator, M. hamifer, M. bivitticollis) or, if reddish pattern is present on pronotum, it is limited at the posterior section of longitudinal dark lines (M. chamorroi, M. praetorius and M. tarsalis). In M. agonista, sclerite I is peculiar, looking very large, intensely pigmented and fused with the controlateral sclerite to form a single shell-shaped lamina. Besides, the denticle and dorsal spicule are completely missing, therefore this lamina is the only sclerified piece facing the block of sclerites III and IV.
The peculiar structure of the endophallus sclerites, with the apparent absence of dorsal spicules, the unusual development of sclerite I and the shape of the apex of sclerite IV clearly distinguishes this species. The aedeagal shape approaches this species to the Metallactus bilineolatus-verrinus group. However, in these last ones the depression on male fifth ventrite is characteristically deep (very shallow, instead, in M. agonista). Moreover, these two species are rather stubby, with cilindrical outline and vaulted pronotum. Conversely, M. agonista has a rather flattened, slim silhouette.
Description of male. BL = 3.9–4.3 mm, BW = 2.2–2.5 mm, PL = 1.4–1.5 mm, PW = 2.0– 2.3 mm. Interocular distance 7.7–11.6% of BL.
Head light brownish with blurred yellow patches above all along the internal ocular rim, Labrum brownish. Vertex quite luster, with well impressed, irregularly distributed punctures, almost bald. Frontoclypeal area with sparse, well impressed punctures, with only very short, scattered setae. Mid-cranial suture short, very shallow so that surrounding surface almost flat. Antennae black, with antennomeres 1-5 partly yellowish.
Pronotum light brownish with lateral margins and longitudinal median stripe, reaching both anterior and posterior margin, yellow. Lateral yellow patch shortly salient along posterior margin. Besides, three black lengthened spots on each side of pronotal surface, two of them, sometimes coalescent, along median yellow stripe, third one in touch with the inner rim of lateral yellow patch. Lateral margin narrowly blackish at least along its anterior and mid section. Pronotal shape roughly subsquared, rather flattened with lateral margins thin, barely visible from above, rather weakly curved with maximum width nearly in the middle. Posterolateral impressions scarcely visible. Surface rather lustrous with scattered, quite impressed punctation, almost equally distributed across the whole surface with the exception of impunctate median yellow stripe.
Scutellum yellow, raised, sub-squared with truncated apex and bare, almost smooth surface.
Elytron yellow with two longitudinal black, posteriorly tapered stripes extended from anterior margin to apical clivus but not reaching apical margin. Lateral row of punctures and suture black to infuscate. Relatively slender, with sides slightly convergent posteriorly and surface very weakly flattened on disc. Postscutellar area not raised. Humeral callus scarcely prominent, impunctate. Surface scarcely lustrous with punctation rather deeply impressed, arranged in almost regular rows, fading behind the middle, almost obliterated on apical clivus. Punctures more confusedly arranged in anterior inner part of disc. Intervals flat. Epipleural surface slightly convex, smooth, devoid of punctation.
Pygidium completely yellow to brownish with sides partly lighter at middle. Surface smooth, matt, with indistinct sparse punctures and whitish setae.
Inferior parts of thorax light brown, sometimes metaepisterna and metasternum with black patches on margins. Hypomera, mesoepimera and mesoepisterna almost bare with scarce shallow punctures. Metaepisterna and metasternum with quite coarse punctation and sparse setae. Prosternal process coarsely punctured with long setae, Abdominal ventrites completely yellow to brownish, shallowly and sparsely punctured, with sparse setae. Legs yellow to brownish, often with tibial apex and tarsi infuscate.
Fifth abdominal ventrite with a median, shallowly impressed, subelliptical depression, smooth, glabrous and impunctate at center, and posterior margin distinctly notched. Median lobe of aedeagus (Fig. 2 c–e) with apex short, blunt with almost straight sides, almost straight in lateral view. Hairy dents fairly impressed, medially separated by a quite sharp tubercle, externally delimited by rounded projections, bearing few short setae. Ventral profile markedly swollen in lateral view. Endophallus (Fig. 2 f–g) with sclerite I very unusually shaped, transformed in a large thick lamina fused with the counterpart on the opposite side, distinctly sclerotized and pigmented, devoid of denticle. Dorsal spicule missing as well. Sclerite II moderately developed, slightly bent at base. Arch of sclerite III quite short, squat. Apex of sclerite III straight, rather upwards directed, pointed, not particularly expanded on its proximal half. Branches of sclerite IV longer than sclerite III in the folded-up structure, with apex remarkably expanded, strongly denticulate on upper rim and surface rather smooth.
Female. Habitus in Fig. 2 a-b (LT). BL = 4.7–4.9 mm, BW = 2.7–2.8 mm, PL = 1.6–1.7 mm, PW = 2.5 mm. Interocular distance 12.2–12.8% of BL. Female differs in stouter body, greater interocular distance. First antennomeres slightly stouter and shorter.
Fifth abdominal ventrite in females with rather deep, slightly transverse elliptical pit, with bottom finely and sparsely punctured. Vasculum of spermatheca (Fig. 2h) robust, scarcely pigmented, compact, with straight proximal branch, short distal branch and apex pointed. Ampulla not 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 rather short, winding. Insertion on bursa copulatrix large, clearly pigmented.
description: Published as part of Sassi, Davide, 2019, Revision of the Metallactus hamifer species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 201-245 in Zootaxa 4657 (2) on pages 208-211, DOI: 10.11646/zootaxa.4657.2.1, http://zenodo.org/record/3763876