Metallactus spilotus Suffrian, 1866

Sassi, Davide, 2018, Revision of the Metallactus kollari species-group with a new diagnosis of the genus (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 4413 (1), pp. 57-110 : 79-82

Metallactus spilotus Suffrian, 1866

( Figs 8 ; 36 )

Metallactus spilotus Suffrian, 1866: 376 ; Clavareau, 1913: 93; Blackwelder, 1946: 641.

Type material. Describing M. spilotus Suffrian (1866) wrote: “ Brasilien (Mus. Schaum) ... in einem einzigen stücke ... ♂ unbekannt”. Therefore, the female housed in MNHUB and labelled: “America, collect. Schaum” must be considered the holotype of the species. Anyway, there is not a complete correspondence between the label data and what Suffrian registered in his monography (see also what has been said on the subject in relation to M. corruptus ). In my opinion this shows that in identifying the types of the species described by Suffrian, it is necessary to interpret wisely the information available, without persisting too much in the search of a complete correspondence between the different sources.

The holotype is identified as follows. HOLOTYPE: ♂, pinned, // “53946” [blue label, handwritten] // “ Metallactus spilotus Suffrian, 1866 HOLOTYPUS D. Sassi det.” [red label, printed] // ( MNHUB). The number on the blue handwritten label corresponds to the data: “53946 spilotus Suffr. 1. America, Collect. Schaum” registered in the old catalogue of MNHUB.

Type locality. “ Brasilien ”.

Further material examined. BRAZIL: Lagoa Santa Reinhardt (1, ZMUC); “Brasilia” Mus. Ahrens (1, ZMUC); “Rio Jan.”, Fry Collection (1, BMNH).

Distribution. Brazil.

Diagnosis. A Metallactus of medium size. It is the only species having pronotal disc almost entirely black and elytra yellow with a large squared black patch on apex. Besides, lateral margin of the pronotum is perceptibly wider than in the other species of the group with the exception of M. bellatrix which is easily distinguishable by the very different overall shape and by dorsal colour pattern. M. spilotus is also very characteristic in having a rather flattened habitus which looks quite different from the cylindrical one of the other species. For this reason, for long I had had some doubt about the closeness of this species to M. kollari group, but the likeness in the aedeagal shape persuaded me to keep it in the same assemblage. The only species rather similar in the flattened shape is M. affinis which differs in elytral black pattern formed by three pairs of rounded spots and in coarser puncturation of pronotum.

Description of male. BL = 4.7–5.3 mm, BW = 3.0– 3.2 mm, PL = 1.5–1.6 mm, PW = 2.6–2.8 mm. Interocular distance 8.5–9.0% of BL.

Head black, sometimes a yellow subtriangular spot extending on upper part of frons and vertex. Labrum brownish with lighter lower rim. Surface dull to lightly lustrous with scattered, quite impressed punctures, denser on clypeus and close the inner ocular rim. A pair of smooth, curved, slightly raised band delimiting frons from clypeus. Setosity sparse, closer on clypeus and labrum. Mid-cranial suture apparent, extended to vertex. Antennae with first five antennomeres more or less brownish, the subsequent totally darkened, dull and more diffusedly setose.

Pronotum yellow with a large elliptical transverse black patch reaching posterior margin and, sometimes, the anterior one on its median trait. Pronotal shape elliptical. Lateral margins quite large with maximum width slightly behind half of length, regularly arcuate but not bent downwards towards anterior corners, so that contemporary visible in dorsal view along the whole length. Posterolateral impressions poorly delimited, shallow but apparent so that posterior margin clearly swollen in front of it. Surface with scattered, rather coarse punctation, sparser on disc.

Scutellum completely black, moderately raised, subsquared with truncated apex. Surface smooth, bald, with very few minute punctures or completely impunctate.

Elytra yellow anteriourly, almost completely black on apical third. Anterior margin black on its median trait, but black colour sometimes extended backwards to form two large subrounded spots reaching periscutellar area. Fairly curved on sides, markedly depressed on disc. Surface dull with punctation quite strong and unevenly arranged, but at least three or four striae detectable from anterior margin to clivus. Intervals flat.

Surface of pygidium totally black or with a pair of oblique yellow spots in continuity with the yellow sides of fifth visible abdominal sternite, covered by sparse shallow punctures and pale setae.

Inferior parts totally black with the exception of a yellow narrow area on side of hypomeron and yellow sides of posterior abdominal sternites. Punctation dense and coarse on pro- and mesothorax. All ventral surface covered by scattered yellowish setae quite regularly arranged. Punctuation regularly distributed and shallow, coarser on hypomera and outer part of metathorax. Prosternal process longitudinally sunken with roughly triangular apex slightly raised on tip and surface coarsely punctured, covered with long dense pale setae. Legs totally black.

Fifth abdominal ventrite with faintly impressed, smooth, bald, impunctate median depression. Posterior margin almost straight. Median lobe of aedeagus ( Fig. 8 c–e) cylindrical with apex short, blunt, poorly distinct from aedeagal tube in ventral view. Hairy dents smooth but quite clearly delimited from the surrounding area, bearing very sparse, tiny setae. In lateral view aedeagal ventral profile slightly depressed on its median part.

Endophallus ( Fig. 8 f–g) with sclerite I well sclerotized, rather small, with a long, robust, sharp, slightly pointing upward denticle. Dorsal spicule well developed, fairly pigmented, conical, sharp, with apex slighlty bent forward. Sclerite II long, abruptly bent near base. Arch of sclerite III fairly lengthened and straight at its basal half, fairly thickened on median part, with apex short. Branches of sclerite IV shorter than sclerite III in the folded up structure, robust, narrowly elliptical with slightly asymmetrical apex and surface fairly rugose.

Female. Habitus in Fig. 8 a–b (HT). BL = 5.4 mm, BW = 3.2 mm, PL = 1.5 mm, PW = 2.8 mm. Interocular distance 12.0% of BL. In the only female examined pronotal black patch almost split in two roughly squared spots by a narrow, longitudinal, deep constriction.

Fifth abdominal ventrite in females with a slightly transverse and rather deep pit. Vasculum of spermatheca ( Fig. 8h ) with lower branch slightly curved and faintly swollen at base, and the upper one straight and regularly tapered in an acute, faintly pigmented apex. Insertions of gland and duct dorsally placed, fairly pigmented. Duct rather tightly coiled in proximal and median part. Non-coiled section rather long. Insertion on bursa copulatrix not swollen, not pigmented. Rectal apparatus ( Fig. 8 k–m) with dorsal sclerites quite deep, regularly tapered towards median line, with apodemes apparent, hyaline, above all towards outer rim. Ventral sclerite narrow, barely tapered on sides, lighter on its central section, with apodemes small, rounded, scarcely protruding.

Figures

FIGURES 7–8. M. languidus (7), M. spilotus (8). 7a–b: habitus; 7c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [1.0 mm]; 7f: sclerites II–III–IV of endophallus [0.8 mm]; 7g: sclerite I and dorsal spicule of endophallus [0.8 mm]; 7h: spermatheca [1.0 mm]; 7k–m: rectal apparatus in dorsal (k) and ventral (m) view [1.0 mm]. 8a–b: habitus; 8c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [1.1 mm]; 8f: sclerites II–III–IV of endophallus [0.7 mm]; 8g: sclerite I and dorsal spicule of endophallus [0.7 mm]; 8h: spermatheca [0.8 mm]; 8k–m: rectal apparatus in dorsal (k) and ventral (m) view [1.0 mm]. 7a–b: lectotype; 8a–b: holotype. Square brackets: length of scale segment.

FIGURES 29–36. Distribution maps for Metallactus kollari species-group. M. languidus (29); M. londonpridei (30); M. longicornis (31); M. patagonicus (32); M. pollens (33); M. regalini (34); M. rileyi (35); M. spilotus (36). Grey squares: localities reported in a generic way.