Metallactus taeniatellus , Suffrian 1866
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus taeniatellus

description: Metallactus taeniatellus Suffrian, 1866
(Figs 8; 18)
Metallactus taeniatellus Suffrian, 1866: 276. Clavareau, 1913: 94 (catalogue); Blackwelder, 1946: 641 (catalogue).
Types. Suffrian (1866) did not mention the number of specimens under study but stated that no males were available for the study. He reported the name of one collector (“Sello”), a single locality (“Allegrette”) for types housed in MNHUB. Besides, he mentioned further studied specimens coming from Clark collection (at present in BMNH). I was able to locate two specimens in BMNH and five specimens in MNHUB, belonging to the type series. Strangely enough, six of them are males. After a careful analysis of all the material that I had the opportunity to examine during the present study, I came to the conclusion that Suffrian misinterpreted the sex of the available specimens. This was probably due to the fact that the median depression on the fifth sclerite of the male is unusually deep in this species, and corresponds well to what Suffrian wrote, thinking he was describing the female anal pit: “Das letzte Segment des ♀ mit einer halbkreisförmigen, glänzenden Grube”. As a matter of fact, the male structure is smooth and shiny at the bottom, whereas the female pit is matt and punctured. A lectotype is here designated as follows: lectotype (by present designation): ♂, glued, aedeagus extracted and glued on the same label bearing the specimen and the dissected abdomen, // “23956” [white label, printed] // “ taeniatellus Suffr. * Allegr. Sellow.” [blue label, handwritten] // “Hist.-Coll. (Coleoptera) Nr. 23956 Metallactus taeniatellus Suffr. * Allegrette, Sellow Zool. Mus. Berlin ” [green label, printed] // “ SYNTYPE Metallactus taeniatellus Suffrian,1866 labelled by MFNB 2013” [red label, printed] // “ Metallactus taeniatellus Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB). Paralectotypes: 4m ♂ #, pinned // “Hist.-Coll. (Coleoptera) Nr. 23956 Metallactus taeniatellus Suffr. * Allegrette, Sellow Zool. Mus. Berlin ” [green label, printed] // “ SYNTYPE Metallactus taeniatellus Suffrian,1866 labelled by MFNB 2013” [red label, printed] // (MNHUB); 1♂, glued, aedeagus extracted and glued on the same label bearing the specimen, abdomen and one leg glued on a separate label, // “44” [blue label, handwritten] // “Brasilia mer” [green label, handwritten] // “M.te video” [green label, handwritten] // “E. Coll. Laferté” [white label, handwritten] // “65.56” [white label, printed] // “a D. Suffrian. determinat.” [white label, printed] // “ Met taeniatellus ” [white label, handwritten] // (BMNH); 1♀, pinned, same data of the previous specimen (BMNH). Label information and the number of syntypes of the specimens in MNHUB match the registration data from the old catalogue of the MNHUB (“23956 Metallactus taeniatellus Suffr. * 5. Allegrette, Sello”). All paralectotypes are also labelled as follows: // “ Metallactus taeniatellus Suffrian, 1866 PARALECTOTYPUS D. Sassi des.” [red label, printed] //.
Type locality. “Brasilia mer”, South Brazil.
Additional material examined. ARGENTINA: Misiones Iguazu 2-25.I.1988 J. Foerster (1, NHMB); Entre Rios Liebig XI.1990 (2, DSPC); Misiones 12 Km SW Sta Ana 21.I.1989 C.W. & L. O’Brien & G. Wibner (1, BYU); Cordoba La Falda I.1945 Coll. Monrós (1, USNMNH); Villa Castelli y Chilecito IV.1954 leg. H. Förster (1, ZSM); Sierra de Cordoba Capella Del Monte (1, MNHUB); Buenos Aires Zelaya I.1958 N. Bornel (4, USNMNH); Buenos Aires Zelaya II.1957 & II.1958 & XII 1959 & XII.1962 Daguerre (15, USNMNH); Buenos Aires San Fernanda XI.1957 Daguerre (2, USNMNH); Tucuman Depto Burruyacù Macomita I.1952 (1, USNMNH); Entre Rios Gualeguaychú Rincón de Landa Coll. Monrós IV.1943 (7, USNMNH); Cordoba Huerto Grande 1000m II.1952 (1, NHMB). BOLIVIA: Coroico (1, SMNS). PARAGUAY: “ Paraguay ” lg. Fiebrig (1, MNHUB); Dept. Cordillera Rio Salado bei Limpio IX.1991 (1, DSPC); Caaguazú Repatriación XI.2000 (1, MSNM); Asuncion Villa Morra Vezényi (2, HNHMB); S. Bernardino K. Fiebrig coll. (1, USNMNH); Sapucai WT Foster coll. (4, USNMNH); Depto Central Capiatà I.99 (6, DSPC); Colonia Independencia 12.VIII.1951 coll. Foester (2, USNMNH); Independencia XI.1950 (1, NHMB); Dept. Guayrà Colonia Independencia X.1990 (1, DSPC); 3 km E Ypacaraí 7.X.1968 at night C.W. & L. O’Brien (3, BYU); 4 km E Ypacaraí 10.X.1968 at night C.W. & L. O’Brien (1, BYU); Centurion Reimoser (3, NMV); Paraguari prov. 20 km W La Colmena 19/ 21.2.2008 Kudrna lg. (4, DSPC); Paraguari Salto Cristal 14.IX.1991 U. Drechsel (1, MSPC). URUGUAY: R. O. del U. [República Oriental del Uruguay] Salto Coll. H. Clavareu 1932 (1, MNHN); Colonia R. 21 Km 194 Arroyo San Pedro 8.II.1989 C.W. & L. O’Brien (1, BYU); 8 Km N Colonia R. 21 9.II.1989 C.W. & L. O’Brien & G. Wibner (1, BYU); Paysandu 1-10.II.1939 P. A. Berry (1, USNMNH).
Distribution. Argentina (new), Bolivia (new), Brazil, Paraguay (new), Uruguay (new).
Diagnosis. The species is chromatically highly variable. In the most frequent pattern, the elytron is mostly yellow in the basal half, while the pronotum is black, with the sides yellow and often a linear median stripe yellow as well (therefore not completely corresponding to the figured lectotype in Fig. 8a–b). On the central section of the posterior pronotal margin there is almost always a yellow marking, evident even at low magnification and contrasting with the surrounding dark colour of the pronotal disc. This is a chromatic aspect sometimes also present (see the above identification key) in individuals of other species of the group, such as M. geiseri, but in M. taeniatellus it is decidedly more frequent and can help discriminate the species. Once again, however, it must be said, given the great chromatic variability within the species group, that the shape of the aedeagal median lobe seems to be the only trait allowing for reliable identification.
Description of male. Habitus in Fig 8a–b (LT). BL = 4.0– 4.4 mm, BW = 2.2–2.5 mm, PL = 1.4–1.6 mm, PW = 1.9–2.3 mm. Interocular distance 6.8–7.5 % of BL.
Head yellow with black stripes bordering inner margin of eyes, broadening in correspondence of canthus. Sometimes yellow pattern reduced to subtriangular spot on frontoclypeal surface. Labrum yellowish. Vertex quite dull with few, scattered punctures, and short setae. Surface of frons and clypeus shiny, with shallow and sparse punctation, denser on lower portion. Setae sparse, scarcely perceptible. Frontal longitudinal groove shallow but apparent between upper half of eyes. Ocular lines narrow, strictly adhering to ocular rim. Ocular canthus deep, with few shallow punctures and short setae mostly arranged in row close to ocular rim. First five antennomeres sublucid, yellowish, 3-5 rod-shaped, 6-11 darkened, dull, more flattened, and more diffusely setose (Fig. 8h).
Pronotum black with yellow stripes along lateral margins, shortly extended along anterior one and short median yellow stripe not reaching margins. Another narrow, transverse, linear (or rarely bilobed) yellow marking along median portion of basal margin. Sometimes pronotum yellow with two bilobed, slightly oblique piceous spots rising from posterior margin and converging forward toward midline. Pronotum tronco-conical in shape, with lateral margins narrow, regularly curved with maximum width behind half of length. Surface moderately lustrous with scattered punctation weakly impressed, equally distributed both on disc and sides. Posterolateral impressions missing, so that posterior margin not swollen toward sides.
Scutellum black, moderately raised, trapezoidal, with truncated apex. Surface smooth, with few, tiny, whitish setae above all on basal half.
Elytron yellow with black longitudinal stripe ranging from anterior margin and reaching base of apical clivus. Suture narrowly darkened. Black stripe may be replaced by transverse band, just behind middle of elytron, extended from suture to lateral margin. Quite often black pattern more developed, leaving yellow patches only on apex, on humeral region and on periscutellar surface. In one specimen elytron almost completely black. Elytral outline parallel-sided, very weakly flattened on disc. Lateral margin narrow, in dorsal view visible from apex up to midline. Surface dull with impressed punctation, quite irregularly arranged in basal half, some evidence of striae on apical clivus. Intervals flat. Postscutellar area not raised. Humeral callus prominent, impunctate. Epipleuron smooth, shiny, impunctate, with mildly convex surface.
Pygidium piceous bordered with yellowish patches, almost bald, covered with sparse, shallow lengthened punctures.
Ventral parts black or piceous, only first visible abdominal ventrites slightly yellow on sides. Hypomera, mesoepimera and mesoepisterna almost glabrous, impunctate or with scarce shallow punctures. Metaepisterna, metasternum and abdominal ventrites densely setose. Prosternal process weakly grooved, sparsely punctured with long setae and slightly raised short triangular apex. Legs yellow with brown patches mostly on femora.
Fifth abdominal ventrite with quite deep, elliptical, transversally arranged, bald, impunctate median depression. Posterior margin barely notched. Median lobe of aedeagus (Fig. 8c–e) slightly compressed laterally with fairly widened, quite pointed triangular apex very weakly bent ventrally in lateral view. Setose depressions deeply impressed, ear-shaped, separated by wide, blunt median carina. Setae short and scattered, mostly visible on external surface of wall laterally delimiting setose depressions. Shaft ventral surface delimited from sides by blunt edges, giving the impression of flat, mildly raised longitudinal carina.
Endophallus (Fig. 8f) with sclerite I weakly sclerotized and pigmented, reduced to flattened fold on edge of membranous part of endophallus, terminated with blunt denticle. Dorsal spicule not detectable. Sclerite II well pigmented, in lateral view with slender process upward directed. Sclerite III sickle-shaped, with expanded arch and very short, blunt, straight apex. Branches of sclerite IV slightly shorter than sclerite III in folded-up structure, weakly arched towards ventral direction, broadened at base and slightly tapered toward blunt apex. Surface of sclerite IV smooth.
Female. BL = 4.4–4.6 mm, BW = 2.5–2.7 mm, PL = 1.5 mm, PW = 2.2–2.3 mm. Interocular distance 9.1–10.9 % of BL.
Females differ in stouter body and larger interocular distance. The yellow pattern on the pronotum is sometimes more extensive, forming two large straight stripes over the outer fourths of the pronotal surface. In other specimens, the yellow colour on the pronotum is reduced to a pair of blurred spots on the posterior corners.
The fifth abdominal ventrite in females has a large, rounded, impressed pit. The bottom of the pit is glabrous, covered with sparse punctures. The vasculum of the spermatheca (Fig. 8g) is moderately pigmented, S-shaped, slender, with the proximal lobe not swollen. The distal lobe is slender, regularly arched, tapered with the apex bent downward. The ampulla is scarcely pigmented, sitting just at the basal apex of the vasculum, short and transverse. The duct and sperm gland insertions are perceptibly distinct. The duct is robust, short, quite rigid beside the vasculum, forming a series of a few turns more than coils, then almost straight and narrower in proximity to the bursa copulatrix. The insertion on the bursa copulatrix is robust, conical, strongly pigmented. In one specimen from Ypacaraí (Paraguay) the vasculum is shorter and stouter with the distal lobe straight.
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 270-273, DOI: 10.11646/zootaxa.5125.3.1, http://zenodo.org/record/6443765