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

description: Metallactus crassicollis Suffrian, 1866
(Figs 7; 24)
Metallactus crassicollis Suffrian, 1866: 329; Clavareau, 1913: 92 (catalogue); Blackwelder, 1946: 641 (catalogue).
Types. Suffrian did not mention the number of specimens under study but he reported the name of a single collector (von Olfers) and a single type depository (MNHUB), where four syntypes have been tracked down. The label information and the number of the specimens match the registration data from the old catalogue of the MNHUB (“23965 Metallactus crassicollis Suffr. * 4. Brasil, v. Olf.”). The typification has been made as follows, in order to stabilize the epithet. LECTOTYPE (by present designation): ♂, glued, aedeagus glued on the same card bearing the specimen, abdomen and sclerites of endophallus glued on a separate card // “23965” [white label, printed] // “ crassicollis Suffr. * Brasil. v. Olf.” [blue label, handwritten] // “Hist.-Coll. (Coleoptera) Nr. 23965 Metallactus crassicollis Suffr. * Brasil., v. Olfers Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus crassicollis Suffrian, 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus crassicollis Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB). PARALECTOTYPES: 2♂ 1♀ // “Hist.-Coll. (Coleoptera) Nr. 23965 Metallactus crassi- collis Suffr.* Brasil., v. Olfers Zool. Mus. Berlin” [green label, printed] // “ SYNTYPE Metallactus crassicollis Suffrian, 1866 labelled by MFNB 2019” [red label, printed] // “ Metallactus crassicollis Suffrian, 1866 PARALECTOTYPUS D. Sassi des.” [red label, printed] // (MNHUB).
Type locality. “ Brazil ”.
Distribution. Brazil.
Diagnosis. A Metallactus of small size. M. luniger is the most similar relative, but easily distinguished in the color of legs, which are black. Moreover, M. luniger can be differentiated by the following features: larger size, rounded or elliptical periscutellar yellow spot on elytron, scutellum at least partly black; rear third of longitudinal median yellow stripe on the pronotum of the same width or slightly enlarged; rear ending of lateral C-shaped yel- low spot on pronotum, along the pronotal posterior margin, rounded and substantially symmetrical (not obliquely cut like in M. crassicollis). Median lobe of aedeagus is rather unusual compared to the “typical” shape in genus Metallactus, being flattened in dorsoventral direction. This somehow reminds of Griburius most common aedeagal pattern, but the endophallus morphology is unquestionably typical of Metallactus species, although still unusual for its small size. The length of sclerite III is about 0,2 mm, about half-length than in related species (M. tarsalis, for instance). Reduced dimension of endophallus may be related to the peculiar shape of the median lobe.
Description of male. Habitus in Fig. 7 a–b (PLT). BL = 3.9–4.3 mm, BW = 2.5–2.7 mm, PL = 1.3–1.5 mm, PW = 2.2–2.4 mm. Interocular distance 7.7–9.3% of BL.
Head yellow with vertex and ocular canthus blackish to frankly black. Lower part of clypeus blackish as well. Labrum yellow. Vertex quite shiny, bare, with few punctures scattered on yellow spot. Frontoclypeal area with sparse pale setae and shallow, sparse punctation prevalently distributed along inner ocular rim and close to antennal socket. Mid-cranial suture short, weakly impressed so that surrounding surface not swollen. All antennomeres unicolored brownish, first five antennomeres sublucid, the subsequent ones dull, more flattened and more diffusedly setose.
Pronotum black with two large C-shaped yellow bands along lateral margins, projecting upwards along the outer third of anterior and posterior margins. Posterior end of such bands obliquely cut in all examined specimens. A rather broad yellow logitudinal stripe extending in middle of disc from anterior to posterior margin. Such stripe faded or abruptly constricted on its posterior third or even splitted into a small irregular rear spot settled just at center of posterior margin. Pronotal shape elliptical. Lateral margins relatively narrow, not visible from above for almost the whole length, regularly curved with maximum width at half length. Posterolateral impressions shallow but clearly perceptible. Surface rather flat, moderately shiny with scattered well impressed punctation.
Scutellum yellow, with sides regularly convergent towards apex moderately raised, bare and very minutely punctured. Apex truncated in a straight line.
Elytral surface black with yellow pattern as follows. A lengthened oblique spot just beside scutellum; a larger, transversal rounded to elliptical spot in middle of disc, a further transversal to backwards arcuate stripe just before apical clivus; a rounded spot on apex. On side a C-shaped patch extending along the external third of anterior margin to anterior third of lateral margin and epipleuron; posterior end of such patch salient across elytral surface and often coalescing with spot in middle of disc. Elytral outline parallel-sided, rather squat, weakly flattened on posterior part of disc. Postscutellar area barely raised. Humeral callus moderately prominent, impunctate. Surface rather shiny with fine but well impressed punctures arranged in irregular rows. Intervals flat.
Pygidium yellow with a transverse winding black patch along upper margin. Apex narrowly bordered with blackish tint. In a single specimen black pattern coalescing along median line. Surface smooth, covered with sparse shallow punctures and whitish setae.
Inferior parts of thorax black with mesoepimera and mesoepisterna brownish. Apex of prosternal process often yellowish. Hypomera and mesoepisterna almost bare, with sparse punctation, mesoepimera bare and almost smooth. Metaepisterna and metasternum with coarse punctation as well and sparse setae. Prosternal process, coarsely punctured with long setae and a slightly raised, short, blunt apex. Abdominal ventrites black with broad yellow border, shallowly and sparsely punctured, with rather long, recumbent setae. Legs ochreous with darker tibiae and tarsi.
Median depression on fifth abdominal ventrite rather deep, elliptical, with bottom smooth and bald. Posterior margin of fifth abdominal ventrite weakly notched. Median lobe of aedeagus (Fig. 7 c–e) rather flattened in dorsoventral direction with apex scarcely separated from the rest of aedeagus, short, with slightly angulate lateral margins and a terminal tiny, sharp denticle. In lateral view apex almost straight. Hairy dents moderately impressed, lengthened, with only scarce, tiny, straight setae along their external margins. Aedeagal ventral surface not swollen in lateral view, devoid of particular structures. Endophallus (Fig. 7g) rather uncommon because of its tiny dimension, with sclerite I weakly developed and pigmented, denticle small, sharp, forwardly directed. Dorsal spicule small, blunt. Sclerite II well developed, quite slender, distinctly bent at base and slightly tapered towards apex. Arch of sclerite III slender, scarcely raised. Apex of sclerite III slightly bent downwards, not expanded on its proximal half. Branches of sclerite IV equivalent in length to sclerite III in the folded-up structure, slightly sinuate, with blunt, almost symmetrical, microdenticulate apex and surface distinctly rugose.
Female. BL = 4.8 mm, BW = 3.0 mm, PL = 1.5 mm, PW = 2.7 mm. Interocular distance 10.4% of BL.
Fifth abdominal ventrite in females with quite large and deep pit. Bottom of pit bald, matt, minutely and very sparsely punctured. Female genitalia not examinated.
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 219-220, DOI: 10.11646/zootaxa.4657.2.1, http://zenodo.org/record/3763876