Metallactus latiusculus Suffrian, 1866

Sassi, Davide, 2022, Revision of the Metallactus taeniatellus species group (Coleoptera: Chrysomelidae: Cryptocephalinae), Zootaxa 5125 (3), pp. 251-282 : 260-261

Metallactus latiusculus Suffrian, 1866

( Figs 3 ; 13 )

Metallactus latiusculus Suffrian, 1866: 261 . 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 “ Venezuela ” as provenance of the species, a single collector (“Moritz”) and a single depository: NMV (“Mus. Vindob.”). A single specimen was found in NMV. The specimen bears a label that appears to be quite recently added. A lectotype is designated as follows: lectotype (by present designation): ♂, glued, aedeagus extracted and glued, together with the abdomen, on the same label bearing the specimen, // “Dr Moritz 1858 Venezuela ” [white label, printed] // “54” [white label, printed] // “ Metallactus latiusculus Suffrian, 1866 LECTOTYPUS D. Sassi des.” [red label, printed] // (NMV).

Type locality. Venezuela .

Additional material examined. TRINIDAD & TOBAGO: Trinidad Piarco Savannah 29.X.1937 (4, BMNH). SURINAME: “Surinam” Heller S. V (1, MNHUB) .

Distribution. Suriname (new), Trinidad & Tobago (new), Venezuela.

Diagnosis. The colour pattern of the specimens examined is similar to that of M. insitivus , but differs in smaller size, in smaller ocular distance in males, in the pronotum more cylindrical, less flattened posteriorly and almost devoid of punctation. The shape of the aedeagal median lobe is very peculiar.

Description of male. Habitus in Fig 3 a-b (LT). BL = 3.4–3.6 mm, BW = 1.3–2.1 mm, PL = 1.8–2.2 mm, PW = 1.8–1.9 mm. Interocular distance 5.6–5.9 % of BL.

Head black with triangular yellow spot on clypeus and lower part of the frons. Labrum brown with yellow border. Vertex quite shiny with few shallow punctures and sparse semi-erect setae. Frontoclypeal area with sparse pale setae and few well impressed punctures only on lighter surface of clypeus. Mid-cranial suture shallow but detectable between ocular rims very close to each other. Ocular lines narrow, strictly adhering to ocular rim. Ocular canthus deep, acute, quite densely punctured with few, sparse semi-erect setae. Antennae ( Fig. 3h ) totally brownish. First five antennomeres sublucid, 3-5 rod-shaped, 6-11 totally darkened, dull, flattened and more diffusely setose.

Pronotum black with two almost straight yellow stripes extending over lateral margins, barely reaching anterior margin. Specimens from Trinidad with crescent-shaped yellow fleck just in front of scutellum and at least hint of short linear stripe at center of disc, yellow. Pronotal shape sub cylindrical, regularly vaulted, apart from central posterior section which is perceptibly depressed. Lateral margins thin, almost not visible in dorsal view, mildly curved with maximum width just behind middle. Surface shining with few, tiny punctures scattered on disc, detectable at medium-high magnification only. Posterolateral impressions not detectable.

Scutellum black, moderately raised, basically impunctate, with very few tiny setae scattered on surface. Apex truncated in straight line.

Elytron dark brownish with one rectangular yellow band covering basal third of surface, extended from lateral margin up to first striae of punctures. Such band darkened on top of humeral callus. Second yellow spot at apex, almost covering whole apical clivus but not reaching posterior margin. Epipleuron totally yellow. Specimens from Trinidad with anterior yellow band irregularly mottled with black and in one specimen this band split in two parts. Elytral outline with sides straight and very little converging posteriorly, slightly flattened on disc. Lateral margins narrow, barely visible from above. Elytral surface moderately shining with close, well impressed punctation, irregularly arranged on basal half, more scattered and less impressed toward apex. Striae barely detectable. On lighter area bottom of punctures darker than interval surface Intervals flat. Postscutellar area not raised. Humeral callus prominent, impunctate. Epipleuron smooth, impunctate, convex, barely bent inward.

Pygidium brownish, smooth, matt, covered by sparse minute punctures and short, 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 as well, impunctate. Rest of ventral surface matt, covered with fine, shallow punctures and short appressed setae. Prosternal process longitudinally grooved, sparsely punctured with long setae and terminated by blunt, not raised, short apex. Legs totally brownish except for yellow-spotted anterior coxae.

Median depression on fifth abdominal ventrite shallow and barely distinguishable from rest of ventrite surface, except for being devoid of setae and punctures. Posterior margin of fifth abdominal ventrite not notched. Median lobe of aedeagus ( Fig. 3c–e ) slightly compressed laterally. Apex gently expanded, shortly triangular, with no clearly differentiated terminal median denticle. In lateral view apex almost straight and ventral outline mildly convex but slightly depressed in middle. Setose depressions shallow, scarcely differentiated from rest of shaft surface and bearing short, sparse setae. Shaft ventral surface delimited from sides by blunt edges, giving impression of flat, mildly raised longitudinal carina.

Endophallus ( Fig. 3f ) with sclerite I laminar, moderately pigmented, twisted, devoid of apical denticle. Dorsal spicule not detectable. Sclerite II small, slender. Arch of sclerite III wide. Apex of sclerite III long, straight. Branches of sclerite IV much shorter than sclerite III in folded-up structure, strongly arched towards ventral direction, with blunt, almost symmetrical, not denticulate apex and surface smooth.

Female. BL = 3.6–3.9 mm, BW = 2.1–2.3 mm, PL = 1.3–1.4 mm, PW = 1.9–2.1 mm. Interocular distance 8.3–10.3 % of BL.

Two females from Trinidad were available for the study. They differ in larger body and wider ocular distance. The yellow spot on the frons is smaller and rounded, and the yellow stripes on the pronotal sides are extended to the the outer fourth of the anterior margin

The fifth abdominal ventrite in females has a quite large and deep pit. The bottom of the pit matt, quite coarsely punctured, with very short sparse setae. The vasculum of the spermatheca ( Fig. 3g ) is scarcely pigmented, S-shaped with a slightly swollen proximal lobe. The distal lobe is slender, long with the apex bent slightly downwards. The ampulla is not pigmented, small, short, rather square, sitting just at the basal apex of the vasculum. The duct and sperm gland insertions are perceptibly distinct. The duct is uniform in size, long, thin, not coiled but forming a short series of loose turns beside the vasculum. The insertion on the bursa copulatrix is weakly sclerotized and pigmented, small, conical.

Remarks. The specimen from Suriname differs slightly from the others in the form of the posterolateral impressions on the pronotum and in a smoother ventral surface of the aedeagal median lobe with no traces of a longitudinal carina. At present it is difficult to give any taxonomic significance to these differences.

Figures

FIGURE 3–4. M. latiusculus. (3). M. multicolor (4). 3a–b: habitus (LT); 3c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.6 mm]; 3f: sclerites of endophallus [0.4 mm]; 3g: spermatheca [0.3 mm]; 3h: antenna [1.1 mm]. 4a–b: habit- us (LT); 4c–e: median lobe of aedeagus in ventral (c), dorsal (d) and lateral (e) view [0.7 mm]; 4f: sclerites of endophallus [0.5 mm]; 4g: spermatheca [0.4 mm]; 4h: antenna [1.3 mm]. scI–IV: sclerites I–IV of endophallus. 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”.