Metallactus albifrons : Suffrian 1866
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2018
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus albifrons

description: Metallactus albifrons Suffrian, 1866
(Figs 5; 21)
Metallactus albifrons Suffrian, 1866: 365; Clavareau, 1913: 92; Blackwelder, 1946: 640.
Metallactus flavofrontalis Jacoby, 1907: 849; Clavareau, 1913: 92; Blackwelder, 1946: 641. n. syn.
Type material. Metallactus albifrons: Suffrian claimed that there were no male specimens in the type series. Only a single female is housed in MNHUB which fits well with the original description. It has been designated as the LECTOTYPE: ♀, pinned, // “ albifrons Suffr. * Brasil v. Olf.” [blue label, handwritten] // “23963” [white label, printed] // “ Metallactus albifrons Jacoby, 1907 LECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB).
Metallactus flavofrontalis: Only a single male is housed in BMNH which fits well with the original description. It has been designated as the LECTOTYPE: ♂, glued, detached abdomen on the same label, aedeagus on a separate label, // “Jatahy Prov. Goyas. Brésil Sept. a Nov. 97 ” [green label, printed] // “Jacoby coll. 1909-28 a.” [white label, printed] // “ Metallactus flavofrontalis Jac. ” [blue label, handwritten] // “Type H T” [round white-red label, printed] // “ Metallactus flavofrontalis Jacoby, 1907 LECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus albifrons Suffrian, 1866 D. Sassi det., 2015” [white label, handwritten] // (BMNH).
Type locality. Metallactus albifrons: Brazil. Metallactus flavofrontalis: Jataí (Goiás, Brazil).
Further material examined. BRAZIL: Mineiros Goiás (4, USNMNH, NHMP, NHMB); Jataí Goiás (2, MNHUB, NHMP); Jataí Goiás IX-XI.1897 (1, USNMNH); Rio Verde Goiás (3, NHMP); Cuiabá Mato Grosso O. Staudinger (1, NHMB); Jaraguá do Sul Santa Catarina (1, USNMNH); Brésil coll. E. Gounelle 1915 (16, MNHN); Mato Grosso Cuijaba (1, MNHN).
Distribution. Brazil.
Diagnosis. A Metallactus of medium size. Contrary to many other species of the group, the dorsal color pattern seems to be rather constant and distinctive in all the examined specimens, for that reason the identification is easy even without the examination of internal characters. The species resembles the darkest forms of M. kollari and M. albipes, from which it can be distinguished by the rounded yellow anterior spots on elytra. In the allied species yellow elytral pattern is always transversally arranged. M. albifrons is also distinguishable by the “high” yellow spot on frons, the scutellum totally or almost totally yellow, the hooked black pronotal spots and the legs completely black. The pronotal outline is also different, being narrower and less transverse. Light pronotal pattern is something more ochraceous than the elytral one, which is pure yellow.
Description of male. BL = 4.9–5.3 mm, BW = 3.0– 3.1 mm, PL = 1.6 mm, PW = 2.5–2.7 mm. Interocular distance 10.5–11.2% of BL.
Head black with a vaguely cordiform slightly raised yellow spot in the center of the forehead. Labrum yellow. Surface with sparse scattered blackish setae and strongly impressed punctures, uniformly distributed except on the cordiform yellow spot which is basically hairless and impunctate. Mid-cranial suture very weakly impressed, slightly deeper close to cordiform yellow spot. First five antennomeres yellowish, 3–5 antennomeres lengthened and sublucid, the subsequent totally darkened, dull and more diffusedly setose.
Pronotum yellow with two large hooked black spots reaching forwards anterior margin on median line, widening outwards, reaching neither posterior margin nor lateral one. Pronotal shape tronco-conical. Lateral margins thin, converging forwards and thus not visible from above. Posterolateral impressions fairly marked, in correspondence of which the posterior margins appear thickened and slightly salient. Surface moderately shining with scattered well impressed punctuation.
Scutellum yellow, sometimes with apical margin narrowly black, dull, distinctly raised, apex truncated in a straight line. Finely setose and minutely punctate.
Elytra surface black with two rounded yellow spots in anterior half, a transversal stripe just before apical clivus (sometimes squeezed or interrupted), a second one, small, just on apex. Outer anterior rounded spot often fused with yellow pattern on lateral margin. Median and posterior stripes externally reaching the lateral margins but leaving suture free along the median line. Epipleura and anterior half of elytral lateral margin yellow as well. Parallel-sided and very weakly flattened on disc. Post-scutellar area not raised. Humeral calli prominent, impunctate. Surface moderately shiny with rather coarse punctures arranged in irregular rows, fairly visible on elytral apex too. Intervals perceptibly raised and connected here and there by faint transverse wrinkles.
Surface of pygidium yellow, smooth, covered by sparse shallow punctures and whitish setae.
Inferior parts black with sides of abdominal ventrites yellow. Surface coarsely punctured with scattered yellowish setae. Prosternal process normally shaped, longitudinally grooved with apex blunt and surface covered with coarse punctures and very long whitish setae. Legs totally black.
Median depression on fifth abdominal ventrite shallow and barely distinguishable from the rest of ventrite surface. Posterior margin of fifth abdominal ventrite weakly notched. Median lobe of aedeagus (Fig. 5 c–e) cylindrical with apex scarcely separated from the rest of aedeagus, short. In lateral view apex faintly bent ventrally. Aedeagal ventral surface barely swollen, devoid of particular structures. Hairy dents moderately impressed, apparent, bearing rather long, dense and curly setae.
Endophallus (Fig. 5 f–g) with sclerite I strongly sclerotized, large, with denticle prominent, blunt, pointing upwards. Dorsal spicule moderate in size, pigmented, cylindrical with a pointed tip. Sclerite II well developed, regularly bent at base. Arch of sclerite III shaped like head of a grebe, being quite short, pointed, with a stout lobate projection on proximal end of upper rim. Branches of sclerite IV sickle-shaped, noticeably shorter than sclerite III in the folded up structure, narrow, evenly thickened, with rounded apex and surface fairly rugose.
Female. Habitus in Fig. 5 a–b. BL = 5.9–6.0 mm, BW = 3.5–3.6 mm, PL = 1.8–1.9 mm, PW = 2.9–3.3 mm. Interocular distance 13.3–14.4% of BL.
Fifth abdominal ventrite in females with quite large and shallow pit. Vasculum of spermatheca (Fig. 5h) scarcely pigmented, compact, with short upper branch and apex blunt, sometimes slightly curved downwards. Ampulla fairly pigmented, slightly shifted on dorsal side of vasculum. Duct and sperm gland insertion very close to each other but perceptibly distinct. Duct of uniform size, slender, coiled, but coils obliterated in the last portion. Insertion on bursa copulatrix lengthened and slightly swollen, clearly pigmented. Rectal apparatus (Figs 5 k–m) with dorsal sclerites laterally not projected beyond rectus, narrow, tapered towards median line and apodemes large, hyaline, bent upwards and leaning against rectum. Ventral sclerite moderately large, ribbon-like, not tapered on sides, less pigmented in middle, with rounded apodemes faintly crenulate on margin and slightly wider than rectum.
Remarks. Jacoby (1907) described Metallactus flavofrontalis on material coming from Jataí (Goiàs, Brazil) without giving any information on the number of the studied specimens. The only syntype housed in BMNH (Fig. 4 a–b) differs from M. albifrons in the reduced dorsal yellow pattern (the anterior yellow elytral band is split into two rounded spots). As a matter of fact, these differences appear to fall within the usual infra-subspecific chromatic variability seen in this group of species. In addition, aedeagal shape shows no differences. Therefore, I propose to consider M. flavofrontalis as a junior synonym of M. albifrons.
description: Published as part of Sassi, Davide, 2018, Revision of the Metallactus kollari species-group with a new diagnosis of the genus (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 57-110 in Zootaxa 4413 (1) on pages 73-74, DOI: 10.11646/zootaxa.4413.1.2, http://zenodo.org/record/3066636