Metallactus geiseri Sassi 2022, sp. nov.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus geiseri

description: Metallactus geiseri Sassi sp. nov.
(Figs 9; 19)
http://zoobank.org/ urn:lsid:zoobank.org:act: C4EB5B59-F38A-4EBF-8FEB-990F6970501D
Types. HOLOTYPE: ♂, body, aedeagus and detached abdomen glued on the same card, // “ Brazil: Mato Grosso Cuiabá, Recanto do Siriema 15°35´31´´S 56°01´33´´W ca. 180 m, 26.II.2020, sweeping & hand collecting” [white label, printed] // “A. A. Mota, M. V. L. Barclay, J. P. Cristóvão, M. F. Geiser & A. Gonzáles-Alvarado leg., BMNH{E} 2020-32” [white label, printed] // “ Griburius cf. multicolor (Jac.) det. M. Geiser 2020” [white label, partly handwritten] // “ Metallactus geiseri sp. nov. HOLOTYPUS D. Sassi des.” [red label, printed] // (CEMT). PARATYPES (7 males and 7 females): 1♂, same data of the holotype; 1♂ 1♀ // “ Brazil: Mato Grosso Cuiabá, Recanto do Siriema 15°35´31´´S 56°01´33´´W ca. 180 m, 16.II.2020 ” [white label, printed] // “A.A. Mota, J. P. Cristóvão & M. G. Geiser leg., sweeping. BMNH{E} 2020-32” [white label, printed] //; 1♂ 1♀ // “ Brazil: Mato Grosso Cuiabá, Recanto do Siriema 15°35´32´´S 56°01´36´´W sweeping, 09.II.2021 ” BMNH{E} 2021-89” [white label, printed] //; 3♂ 1♀ // “ Brazil: Mato Grosso Cuiabá UFMT campus 17-20.II.2020, ca. 170 m, 15°36´33´´S 56°04´05´´W, sweeping & hand collecting” [white label, printed] // “A.A. Mota, M. F. Geiser, A. Bach, L. Coradini, & D. F. Rodriguez leg.” // “BMNH{E} 2020-32” [white label, printed] //; 1♂ 4♀ // “ Brazil: Mato Grosso Cuiabá UFMT Campus 15°36´33´´S 56°04´04´´W ca. 170 m, 18-27.IX.2018, M. Geiser & J. Cristóvão leg., sweeping & hand collecting” [white label, printed] // “BMNH {E} 2018-179” [white label, printed] //. Paratypes are housed in CEMT, BMNH and DSPC. All paratypes provided with additional label: // “ Metallactus geiseri sp. nov. PARATYPUS D. Sassi des.” [red label, printed] //.
Etymology. The species is named after Dr. Michael Geiser, Coleoptera curator at The Natural History Museum in London, U.K., who collected specimens of the new species and kindly allowed me to study them.
Type locality. Recanto do Siriema (Cuiabá, Mato Grosso, Brazil).
Distribution. Brazil.
Diagnosis. The most similar species to M. geiseri in colouration is M. taeniatellus, and the strong chromatic variability makes the attribution of specimens to one or to the other species problematic based on this characteristic alone; however, on the ventral surface of the aedeagal median lobe, the setose depression on each side in M. geiseri is downwardly sharply delimited from the deep rounded pit, while in M. taeniatellus, the setose depressions and pits are not clearly separated from each other. The longitudinal median carina is also significantly wider at the aedeagal apex in M. geiseri than in M. taeniatellus.
Description of male. Habitus in Fig. 9a–b (HT). BL = 3.3–4.1 mm, BW = 1.9–2.4 mm, PL = 1.2–1.4 mm, PW = 1.7–2.1 mm. Interocular distance 4.9–6.1 % of BL.
Head black with bell-shaped yellow marking on frons and clypeus. Small sickle-shaped yellow spot along upper margin of eyes. Labrum piceous, slightly lighter on sides. Vertex quite dull with few, scattered setigerous punctures close to eyes margins. Frontoclypeal area with sparse, pale setae above all along eyes rim, and few shallow punctures. Mid-cranial suture short, well impressed. Ocular lines narrow, strictly adhering to ocular rim. Ocular canthus deep, quite densely punctured with short, semi-erect setae. First five antennomeres sublucid, yellowish, 3-5 rod-shaped, 6-11 totally darkened, dull, more flattened, and more diffusely setose (Fig. 9h).
Pronotum black with yellow pattern as follows: two large yellow stripes along lateral margins, briefly widened close to anterior margin; linear stripe along median line, sometimes very short or missing, not reaching anterior and posterior margins; little U-shaped spot just in front of scutellum. Sometimes this U-shaped spot almost straightened in narrow transverse band running along central section of posterior margin. Pronotal shape tronco-conical. Lateral margins thin, almost not visible in dorsal view, evenly and mildly curved with maximum width just behind half length. Surface moderately shiny with scattered, very fine, slightly lengthened punctation in central part of disc, rounded and coarser toward sides. Posterolateral impressions shallow but detectable.
Scutellum black, moderately raised, trapezoidal, with truncated apex. Surface smooth, with few, tiny, recumbent, whitish setae.
Elytron yellow with large black band just behind midline, extended from suture to lateral margin, often broadened at middle in angulate, forwardly directed projection. Suture narrowly black. Epipleuron yellow, narrowly darkened along margin. Elytral outline parallel-sided, very weakly flattened on disc. Lateral margin narrow, in dorsal view visible from apex up to midline. Elytral surface moderately shiny with well impressed punctures arranged in almost regular rows, easily discernible on elytral apex. On lighter area bottom of punctures only slightly darker than interval surface. Intervals flat. Postscutellar area not raised. Humeral callus prominent, impunctate. Epipleuron smooth, impunctate, with mildly convex surface.
Pygidium piceous with yellow patches along sides, covered with recumbent whitish setae and sparse shallow punctures.
Ventral parts of thorax piceous with first visible abdominal ventrites bordered with yellow. Hypomera, mesoepimera and mesoepisterna almost glabrous, impunctate or with scarce shallow punctures. Metaepisterna, metasternum and abdominal ventrites densely setose. Prosternal process weakly grooved, sparsely punctured with long setae, and slightly raised short triangular apex. Legs yellow to brownish, often with tibial apex and tarsi infuscate.
Fifth abdominal ventrite with deep, elliptical, transversally arranged, bald, impunctate median depression. Posterior margin almost straight. Median lobe of aedeagus (Fig. 9c–e) almost square in transverse section, slightly compressed laterally with fairly widened, bluntly triangular apex. Setose depressions deeply impressed, ear-shaped, with setae short and scattered, also distributed along lateral rim of wide, flat, longitudinal carina running across whole ventral surface. Setose depression neatly separated downward by sharp rim from large, deep, elliptical pit. Aedeagal ventral surface convex in lateral view with a large depression at middle.
Endophallus (Fig. 9f) with sclerite I weakly sclerotized and pigmented, reduced to flattened fold on edge of membranous part, terminated with small denticle. Dorsal spicule not detectable. Sclerite II well pigmented, in lateral view slightly lengthened with slender process upward directed. Sclerite III sickle-shaped, with rounded arch and very short, blunt, straight apex. Branches of sclerite IV slightly shorter than sclerite III in folded-up structure, regularly arched towards ventral direction, weakly broadened at base. Surface of sclerite IV smooth.
Female. BL = 4.3–4.6 mm, BW = 2.6–2.8 mm, PL = 1.5–1.6 mm, PW = 2.3–2.6 mm. Interocular distance 11.6–13.0 % of BL.
Females differ in a stouter body and wider interocular distance. The light colour pattern on the head is reduced to a small, subrounded spot at the center of the frontoclypeal area; the lateral pronotal yellow stripes are fairly wide and the remainder of yellow patches on pronotum are missing.
The vasculum of the spermatheca (Fig. 9g) is moderately pigmented, S-shaped, slender, with the proximal lobe not swollen. The distal lobe is long, slender, rather straight along the median section, then tapered and bent downward at the apex. The ampulla is scarcely pigmented, sitting just at the basal apex of the vasculum. The duct and sperm gland insertions are perceptibly distinct. The duct is short, quite rigid near the vasculum, forming a series of several turns more than coils, then almost straight, more slender in proximity to the bursa copulatrix. The insertion on the bursa copulatrix is robust, shortly conical, strongly pigmented.
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 273-275, DOI: 10.11646/zootaxa.5125.3.1, http://zenodo.org/record/6443765