Metallactus insitivus Suffrian, 1866

Sassi, Davide, 2022, Revision of the Metallactus taeniatellus species group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 5125 (3), pp. 251-282 : 257-259

Metallactus insitivus Suffrian, 1866

( Figs 2 ; 12 )

Metallactus insitivus Suffrian, 1866: 258 . Clavareau, 1913: 93 (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 a generic “ Brasilien ” as provenance of the species, and a single depository: NMV (“Mus. Vindob.”). A single specimen was traced in NMV. The specimen bears a label that appear to be quite recently added, certainly attached much after Suffrian’s study.As a matter of fact, none of Vienna’s specimens of assumed Suffrian’s types bring clues of original labels, because all of them have been replaced by recent printed labels. The matter was discussed in depth in a previous paper ( Sassi, 2018) when designating the LT of M. corruptus Suffrian 1866 . For the same reasons given there and not repeated in detail here again, I am convinced, nonetheless, that the specimen housed in NMV must be considered as belonging to the type series. It has also to be said, again quite surprisingly, that the specimen is a male. That said, I am quite sure that Suffrian misinterpreted the sex of the specimen (see also the discussion about M. taeniatellus ). This was probably due to the fact that, in this species group of Metallactus , the median depression on the fifth sclerite of the male is often deep, the ventral abdominal profile is not perceptibly concave, and the interocular distance in males is not as narrow as it is in most other Pachybrachina species. Moreover, the description of what Suffrian supposed to be “...das letzte Segment des ♀ mit einer halbkugelingen Grube”, matches quite well the shape of the male fifth abdominal sclerite. A lectotype is designated as follow: lectotype (by present designation): ♂, glued, aedeagus extracted and glued, together with the abdomen, on the same label bearing the specimen, // “Trisanga Brasilien Natterer” [white label, printed] // “ Metallactus insitivus Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (NMV).

Type locality. Brazil. Unfortunately, no further information was reported by Suffrian in the original description; however, it should be noted that “Trisanga” is certainly a misspelling for Irisanga (= Orissanga), in the State of São Paulo, in the upper Rio Paraná, a site undoubtedly visited by Natterer ( Schifter, 1993). In the original description, Suffrian does not mention specific localities nor the name of the collector, as he generally did in other cases. In light of the foregoing considerations, I am convinced that Suffrian, on this occasion and in other similar cases, didn’t fully report all the collection data, or some information was unavailable to him when he acquired the material for study (see also Sassi, 2018).

Distribution. Brazil.

Diagnosis. In the only specimen available, the lectotype, the chromatic pattern seems quite characteristic, with the yellow pattern consisting only of the lateral stripe and a median linear one on the pronotum, a subquadrate spot on the humerus and a second one at the apex of the elytron. This chromatic combination has not been observed so far in other species of the group. The availability of additional material would be necessary to confirm the stability of the colour pattern; however, the shape of the aedeagal median lobe is definitive.

Description of male. Habitus in Fig 2 a-b (LT). BL = 4.6 mm, BW = 1.6 mm, PL = 2.8 mm, PW = 2.5 mm. Interocular distance 8.7 % of BL.

Head black with large, subtriangular yellow spot on lower part of frontoclypeal area. Surface covered with coarse, well impressed punctures and sparse appressed setae. Mid-cranial groove short, narrow but well impressed. Ocular lines narrow, strictly adhering to ocular rim. Ocular canthus deep, matt, with few shallow punctures and sparse very short setae. Antennomeres 2-5 yellowish, moderately lengthened, 6-11 totally darkened, dull, flattened and more diffusely setose ( Fig. 2h ).

Pronotum black with two large hooked yellow stripes extending over lateral margins and outer fourth of anterior margin. Narrowly elliptical yellow stripe along median line, not reaching anterior and posterior margins. Posterior margin with yellow marking just in front of scutellum. Pronotal shape elliptical, slightly flattened on disc towards base. Lateral margins thin, almost not visible in dorsal view, evenly curved with maximum width just behind half length. Surface shining with scattered, evenly distributed, well impressed punctation. Posterolateral impressions not detectable.

Scutellum black with yellow fleck in middle, moderately raised, finely setose and minutely punctured. Apex truncated in straight line.

Elytron black with one almost square yellow spot covering humeral region, extended from lateral margin to almost midline of elytron. Such spot darkened on top of humeral callus. Second yellow spot at apex, almost covering whole apical clivus. Epipleuron totally yellow. Elytral outline with sides straight and slightly convergent posteriorly, fairly flattened on disc. Lateral margins narrow, barely visible from above. Elytral surface moderately shining with close, well impressed punctation, irregularly arranged. On lighter area bottom of punctures darker than interval surface. Intervals flat. Postscutellar area not raised. Humeral callus prominent, impunctate. Epipleuron smooth, impunctate, strongly convex, barely bent inward.

Pygidium black with two hooked yellow spots along sides, smooth, matt, covered by sparse minute punctures and short, appressed, pale setae.

Ventral parts of thorax totally black.Abdominal ventrites dark brown with yellow border along sides. Hypomera shiny, bare, covered with well impressed punctures on anterior part. Mesoepimera and mesoepisterna polished and bare as well, impunctate. Rest of ventral surface matt, covered with fine, shallow punctures partly lengthened transversally and short appressed setae. Prosternal process longitudinally grooved, sparsely punctured with long setae and raised short triangular apex. Legs totally black except yellow-spotted anterior coxae and posterior femora, partly yellow.

Median depression on fifth abdominal ventrite deeply impressed, bluntly triangular, shiny, glabrous, impunctate, with posterior margin almost straight. Median lobe of aedeagus ( Fig. 2c–e ) slightly compressed laterally, with apex mildly expanded, barely differentiated from shaft, shortly triangular, terminated by a small median denticle. In lateral view apex almost straight. Ventral outline slightly convex but clearly depressed in middle. Setose depressions deeply impressed, apparent, separated by a narrow, short carina and bearing rather long, curly, sparse setae. Ventral surface delimited from sides by distinct edges.

Endophallus ( Fig. 2f ) with sclerite I reduced to a ribbon-like weak lamina devoid of denticle or other structure. Dorsal spicule not detectable. Sclerite II small, squared, strongly pigmented. Sclerite III unusual, robust, almost straight, barely tapering at apex. Branches of sclerite IV much shorter than sclerite III in folded-up structure, distinctly arched towards ventral direction with a blunt apex and surface smooth.

Female. Unknown

Figures

FIGURES 1–2. M. cultus (1), M. insitivus (2). 1a–b: habitus (PLT); 1c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.9 mm]; 1f: sclerites of endophallus [0.2 mm]; 1g: spermatheca [0.5 mm]; 1h: antenna [1.3 mm]. 2a–b: habitus (LT); 2c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 2f: sclerites of endophallus [0.4 mm]; 2g: antenna [1.4 mm]. scI–IV: sclerites I–IV of endophallus; am: ampulla of spermatheca; dt: ductus of spermatheca; isr: ductus insertion on bursa copulatrix; vs: vasculum of spermatheca. Square brackets: length of scale segment.

FIGURES 11–14. Distribution maps for the Metallactus taeniatellus species group. M. cultus (11); M. insitivus (12); M. latiusculus (13); M. multicolor (14). Grey squares: generic localization for specimens briefly labeled as coming from “Venezuela” and “Suriname”.