Metallactus superbiens D. Sassi 2022, n. comb.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus superbiens

description: Metallactus superbiens (Suffrian, 1866) n. comb.
(Figs 7; 17)
Scolochrus superbiens Suffrian, 1866: 231.
Griburius superbiens Clavareau, 1913: 94 (catalogue); Blackwelder, 1946: 640 (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 single locality (“S. Arem”) for types housed in “Mus. Baly”, at present in BMNH. Three female syntypes were found in BMNH.A lectotype is here designated as follows: lectotype (by present designation): ♀, pinned, // “981” [white label, handwritten] // “66” [white label, handwritten] // “Santarem” [round, white label, handwritten] // “Baly Coll.” [white label, printed] // “Type Suffr Coll Baly” [white label, handwritten] // “Scolochrus superbiens Suffr Amazons ” [white label, handwritten] // “ Griburius superbiens (Suffrian, 1866) (Sc olochrus superbiens) LECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus superbiens (Suffrian, 1866) D. Sassi det. 2021” [white label, printed] // (BMNH). Paralectotypes: 2 ♀, pinned, // “Santarem” [round, blue label, handwritten // “ Griburius superbiens (Suffrian, 1866) (S colochrus superbiens) PARALECTOTYPUS D. Sassi des.” [red label, printed] // “ Metallactus superbiens (Suffrian, 1866) D. Sassi det. 2021” [white label, printed] // (BMNH).
Type locality. Santarém (Pará, Brazil).
Additional material examined. BRAZIL: Amazon Bates Riv. Tapyos (1, BMNH); Santarem (1, BMNH); Amazon River Parà, 1995.04 Marajó Island (1, DSPC); Natal, Rio Grande do Norte F. Monrós Collection 1959 (2, US-NMNH). FRENCH GUIANA: Gourdonville X.1914 R. Benoist (1, MNHN).
Distribution. Brazil, French Guiana (new).
Diagnosis. The species was described as belonging to the genus Scolochrus (now Griburius), but the shape of the male genitalia, the morphology of the pronotal process, the ocular distance and the overall outline clearly suggest a transfer to the genus Metallactus. In the studied specimens the pronotal colour pattern is rather uniform (Fig. 7 a-b), except for a male from Marajó Island, in which the longitudinal median stripe is almost obliterated. A similar chromatic arrangement on the pronotum is observed in some specimens of M. geiseri and M. uncinatus, but the light colouration on the elytron is usually more extensive (M. geiseri) or differently arranged (M. uncinatus). The comparison of the aedeagal median lobe enables one to determine specimens of these species without any difficulty.
Description of male. BL = 3.3–3.9 mm, BW = 2.0– 2.3 mm, PL = 1.2–1.4 mm, PW = 1.8–2.2 mm. Interocular distance 3.0–5.1 % of BL.
Head black with bell-shaped yellow spot on clypeus. Sometimes with small sickle-shaped yellow spot along upper margin of eyes and tiny rounded one at corner of ocular canthus. Labrum brownish. Surface covered with sparse short semi-erect setae and shallow punctation above all on darker patches. Mid-cranial suture fine, barely detectable along vertex and upper part of frons. Ocular lines narrow, strictly adhering to ocular rim, marked by line of punctures that seeps into ocular canthus, whose surface impunctate elsewhere. Ocular canthus deep, acute with few, sparse semi-erect setae. First five antennomeres sublucid, yellowish, 3-5 rod-shaped, the 6-11 totally darkened, dull, flattened and more diffusely setose (Fig. 7h).
Pronotum black with two large hooked yellow stripes extending over lateral margins and outer third of anterior margin. Short, linear yellow spot just at center of disc. Transverse crescent-shaped yellow mark along basal margin just in front of scutellum. Pronotal shape tronco-conical, fairly flattened on disc towards base. Lateral margins thin, almost not visible in dorsal view, evenly curved with maximum width just behind middle. Surface shining with scattered, moderately impressed punctation. Posterolateral impressions shallow but detectable.
Scutellum black, distinctly raised, finely setose and minutely punctured. Apex truncated in straight line.
Elytron black with yellow marking covering inner part of basal margin and extended to periscutellar area. Second crescent-shaped yellow marking on apex. Yellow spot at basal angle, external to humeral callus, extended to epipleuron. In one specimen yellow colour more extensive, and black pattern reduced to small spot on humerus and large angular band on middle part of disc, running from suture to lateral margin. Elytral outline parallel-sided, rather narrow, with sides slightly convergent posteriorly. Elytron disc weakly flattened on posterior part. Lateral margin narrow, in dorsal view barely visible from apex up to midline. Elytral surface weakly shiny, covered with well-impressed punctures arranged in almost regular rows. On lighter area bottom of punctures darker than interval surface. Intervals flat. Postscutellar area mildly raised. Humeral callus prominent, impunctate. Epipleuron smooth, impunctate, rather convex.
Pygidium brownish with two linear yellow spots along sides, smooth, matt, covered by sparse shallow minute punctures and appressed setae.
Ventral parts of thorax totally dark brownish. 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, impunctate. Rest of ventral surface matt, covered with fine, shallow punctures and short recumbent setae. Prosternal process rather large along basal half, with apparent longitudinal groove, sparsely punctured with, long setae and terminated by blunt, slightly raised, short apex. Legs brownish with lighter distal part of tibiae and tarsi. Apex of mid and posterior femora and anterior coxae with yellow patches.
Median depression on fifth abdominal ventrite shallow but fairly delimited from the rest of ventrite surface, shiny, bare and impunctate. Ventrite posterior margin raised, straight. Median lobe of aedeagus (Fig. 7c–e) cylindrical with expanded, well differentiated, lancet-shaped apex, devoid of real denticle but terminated with sharp tip. In lateral view outline slightly depressed in middle. Setose depressions shallow with few setae short and scattered.
Endophallus (Fig. 7f) with sclerite I vaguely sickle-shaped, devoid of clear apical denticle. Dorsal spicule not detectable. Sclerite II small, well pigmented, lengthened. Sclerite III forming rather wide arch. Branches of sclerite IV shorter than sclerite III in folded-up structure, distinctly arched towards ventral direction, slender, with blunt apex and surface smooth. Base of sclerite IV broadened.
Female. Habitus in Fig. 7a–b (LT). BL = 4.1 mm, BW = 2.4–2.5 mm, PL = 1.3–1.4 mm, PW = 2.2 mm. Interocular distance 9.8–12.2 % of BL.
Females differ in a stouter body and wider interocular distance. In one specimen the yellow colour is more extensive, and the black pattern reduced to a small spot on the humerus and a longitudinal stripe along the midline of the elytron, broadened in the rear half to join the lateral margin.
The fifth abdominal ventrite in females has a quite large, rounded, impressed pit. The bottom of the pit is glabrous, matt, finely rugulose. The vasculum of the spermatheca (Fig. 7g) is very unusual in the single available specimen being S-shaped with a corkscrew-like appearance. The proximal lobe is moderately pigmented, slightly swollen. The distal lobe is slender, tapered, with the apex slightly bent downward. The ampulla is fairly pigmented, sitting just at the basal apex of the vasculum, shortly conical. The duct and sperm gland insertions are perceptibly distinct. The duct is long, quite rigid near the vasculum, more slender and more delicate towards the bursa copulatrix, forming loose turns both near the vasculum and in proximity to the bursa copulatrix. The insertion on the bursa copulatrix is robust, conical, strongly pigmented.
Remarks. The two specimens (one male and one female) from Natal, in Rio Grande do Norte, differ remarkably in some ways. In particular, the pronotum is mostly yellow with an M-shaped black patch on the disc. The elytron is mostly yellow as well, with two longitudinal black stripes extended from the base to apex, the inner one, larger, in the middle of the elytron, the second one along margin. The suture is narrowly black. Additionally, the median lobe of the aedeagus is slightly more regularly convex in lateral view. Nevertheless, I am inclined to consider the specimens as belonging to this species, at least provisionally, based above all on the overall similarity in the shape of the median lobe.
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 268-270, DOI: 10.11646/zootaxa.5125.3.1, http://zenodo.org/record/6443765