Metallactus uncinatus Sassi, 2022

Sassi, Davide, 2022, Revision of the Metallactus taeniatellus species group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 5125 (3), pp. 251-282 : 275-280

Metallactus uncinatus Sassi sp. nov.

( Figs 10 ; 20 )

http://zoobank.org/ urn:lsid:zoobank.org:act:1BF0EE69-1551-4D74-8CAE-21330338CAF1

Types. HOLOTYPE: ♂, body, aedeagus and detached abdomen glued on the same card, // “ Brazil: Mato Grosso 12°50´S 51°47´W 17.III.1968 O. V. Richards R. S. & R. G. S. Exped. B. M. 1968-260” [white label, printed] // “ Campo ” [white label, printed] // “ Metallactus uncinatus sp. nov. HOLOTYPUS D. Sassi des.” [red label, printed] // ( BMNH). PARATYPES (2 specimens, 1 male and 1 female dissected to check genitalia): 1♂ // “ Brazil: Mato Grosso 12°50´S 51°45´W 15.III.-8.IV. 1968 B. E. Freeman ” [white label, printed] // “Campo” [white label, printed] // “Roy. Soc- Roy. Geog. Soc. Xavantina—Cachimbo Exped. 1967-69” [white label, printed] // “Brit. Mus. 1973- 292” [white label, printed] // ( DSPC); 1♀ // “ Brazil: Mato Grosso 12°50´S 51°45´W 10-28.III.1968 B. E. Freeman ” [white label, printed] // “ Dry forest ” [white label, printed] // “Roy. Soc- Roy. Geog. Soc. Xavantina—Cachimbo Exped. 1967-69” [white label, printed] // “Brit. Mus. 1973-292” [white label, printed] // ( BMNH). Both paratypes provided with additional label: // “ Metallactus uncinatus sp. nov. PARATYPUS D. Sassi des.” [red label, printed] //.

Etymology. Latin past participle “uncinatus” meaning “hooked”, “clasped”, stressing the shape of the longitudinal elytral black stripes, hooked to each other by transverse connections.

Type locality. Albeit not explicitly reported, the geographic coordinates on the label point to Ribeirão Cascalheira (Mato Grosso, Brazil) as the type locality of the species .

Distribution. Brazil.

Diagnosis. The presence of two longitudinal black stripes on the elytra, transversely connected once or twice to each other, makes this species quite different from all others considered in this study; however, the number of specimens available is very limited and does not allow an understanding of the real chromatic variability within the species. For this reason, once again the aedeagal morphology allows for better species discrimination.

Description of male. Habitus in Fig. 10a–b (HT). BL = 3.6 mm, BW = 2.2–2.3 mm, PL = 1.3–1.4 mm, PW = 2.0– 2.1 mm. Interocular distance 5.6 % of BL.

Head black with three-lobed yellow spot on lower part of frons and clypeus. Labrum yellowish. Vertex quite dull, shallowly and sparsely punctured with few, short recumbent setae. Frontoclypeal area finely and uniformly punctured, with short, sparse setae. Mid-cranial suture rather long, well impressed. Ocular lines well-impressed, strictly adhering to ocular rim. Ocular canthus deep, acute, with surface devoid of punctures, bearing very short setae. First five antennomeres sublucid, yellowish, 3-5 rod-shaped, 6-11 totally darkened, dull, more flattened, and more diffusely setose ( Fig. 10h ).

Pronotum black with yellow pattern as follows: two yellow stripes along lateral margins, projecting upwards along outer fourth of anterior margin; short linear stripe along median line not reaching anterior and posterior margins; bilobed spot just in front of scutellum. 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 well marked punctures, slightly stronger in posterior and lateral part of disc. Posterolateral impressions very shallow, barely perceptible.

Scutellum black, moderately raised, trapezoidal, with truncated apex. Surface sparsely punctate, with few, tiny, recumbent, whitish setae.

Elytron yellow with suture black and two longitudinal black stripes running from elytral base to clivus. The outer one, extended between sixth and ninth rows of punctures, covering humeral callus and reaching elytral apex up to sutural angle, meeting black pattern of suture. Inner black stripe shorter, extended between second and fifth row of punctures, not reaching basal and apical margins, slightly tapered backwards. One specimen ( Fig. 10 a-b) with black stripes transversally connected to each other at middle of elytron and just before apical clivus. However, one connection between the two stripes (before apical clivus) present in all of available specimens. Elytral outline parallel-sided very weakly flattened on disc. Lateral margin narrow, in dorsal view visible from apex up to midline. Surface dull with fine punctures in almost regular rows, only on anterior inner part of disc punctation quite confusedly arranged. On lighter area bottom of punctures only slightly darker than interval surface. Intervals flat. Postscutellar area not raised. Humeral callus moderately prominent, impunctate. Epipleuron smooth, impunctate, with mildly convex surface.

Pygidium piceous with yellow patches along sides. Surface matt, 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 raised short triangular apex. Legs yellow with darker patches, basal three quarters of femora piceous.

Fifth abdominal ventrite with moderately deep, elliptical, transversally arranged, bald, impunctate median depression. Posterior margin almost straight. Median lobe of aedeagus ( Fig. 10c–e ) cylindrical along proximal section with widened, truncated apex terminated by small blunt denticle. Setose depressions shifted on apical sides, linear, raised, with few, short, thickened setae. Short, apical carina connecting apical denticle to medial section of ventral surface. Aedeagal ventral surface regularly convex in lateral view.

Endophallus ( Fig. 10f ) with sclerite I in form of blunt slender rib, devoid of clearly detectable terminal denticle. Dorsal spicule not detectable. Sclerite II well sclerotized, subquadrate. Sclerite III rather straight directed, forming wide arch and short, blunt apex. Branches of sclerite IV shorter than sclerite III in folded-up structure, regularly arched towards ventral direction, fairly broadened at base. Surface of sclerite IV smooth.

Female. BL = 4.3 mm, BW = 2.6 mm, PL = 1.5 mm, PW = 2.4 mm. Interocular distance 9.3 % of BL.

Females differ in a stouter body and wider interocular distance.

The vasculum of the spermatheca ( Fig. 10g ) is moderately pigmented, S-shaped, slender, with the proximal lobe not swollen. The distal lobe is slender, mildly curved proximally, then slightly tapering 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 rather short, uniform in thickness, quite rigid beside the vasculum, forming a series of several wide and loose turns more than coils, then almost straight in proximity to the bursa copulatrix. The insertion on the bursa copulatrix is shortly conical, strongly pigmented.

Figures

FIGURES 9–10. M. geiseri (9), M. uncinatus (10). 9a–b: habitus (HT); 9c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 9f: sclerites of endophallus [0.5 mm]; 9g: spermatheca [0.3 mm]; 9h: antenna [1.2 mm]. 10a–b: habitus (HT); 10c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 10f: sclerites of endophal- lus [0.3 mm]; 10g: spermatheca [0.4 mm]; 10h: antenna [1.3 mm]. scI–IV: sclerites I–IV of endophallus. Square brackets: length of scale segment.

FIGURES 19–20. Distribution maps for the Metallactus taeniatellus species group. M. geiseri (19); M. uncinatus (20).