Metallactus tommasoi Sassi, 2025, sp. nov.
Creators: name: Sassi, Davide
Publisher: name: Zenodo
Year: 2025
Subjects: Biodiversity
Taxonomy
Animalia
Arthropoda
Insecta
Coleoptera
Chrysomelidae
Metallactus
Metallactus tommasoi

description: Metallactus tommasoi sp. nov.
urn:lsid:zoobank.org:act: 4A89F110-2366-4590-968A-23B02B1431F0
(Figs 3; 4e–g; 5c; 6c)
Types. HOLOTYPE: ARGENTINA: Buenos Aires: ♂, glued, detached abdomen glued on the same card, median lobe of aedeagus glued on a separate card, // “ARGENTINA Bs. AIRES, Felipe Sola (Bahia Blanca) coll. Monrós En. 942” [white label, handwritten] // “F. Monros Collection 1959” [White label, printed] // “ Metallactus tommasoi sp. nov. HOLOTYPUS D. Sassi des.” [red label, printed] // (USNMNH). PARATYPES (24): ARGENTINA: Buenos Aires: 2♂ 1♀, same data as the holotype (USNMNH & DSPC); 4♀ // “ ARGENTINA Bs. AIRES, Bahia Blanca Felipe Sola coll. Monrós Feb. 942” [white label, handwritten] // “F. Monros Collection 1959” [White label, printed] // (USNMNH); 7♂ 2♀ // “ ARGENTINA Bs. AIRES, Felipe Solá coll. Monrós Feb. 942” [white label, handwritten] // “F. Monros Collection 1959” [White label, printed] // (USNMNH & DSPC); 3♂ // “ ARGENTINA Bs. AIRES, Tandil coll. Monrós En. 1941” [white label, handwritten] // “F. Monros Collection 1959” [White label, printed] // (USNMNH & DSPC); 1♀ // “ ARGENTINIEN Prov. Buenos Aires Sierra de la Ventana 20.3.54 [white label, partly handwritten] // “Zool. Staatslg. M,nchen” [White label, printed] // (ZSM). Córdoba: 4♀ // “CORDOBA - ARGENTINA Dep. de Calamuchita El Sauce XII-1938 Manuel J. Viana [white label, printed] // “F. Monros Collection 1959” [White label, printed] // (USNMNH & DSPC). All paratypes also labelled: // “ Metallactus tommasoi sp. nov. PARATYPUS D. Sassi des.” [red label, printed] //.
Additional material examined.A single female was examined, bearing the following information: PARAGUAY: Caaguazu: Morombi 12–15.XII.2013 (UDPC). The specimen is slightly larger than the recorded range for females of the new species. Additionally, its coloration is partly different, with the elytra being completely yellow except for a small, rounded spot at the apex. Despite matching the rest of the observed characteristics, it was deemed more prudent not to consider this specimen as part of the type series of the new species. Therefore, the presence of Metallactus tommasoi in Paraguay remains doubtful, pending further confirmation.
Type locality. Felipe Solá (Buenos Aires, Argentina).
Etymology. The new species is dedicated to my son Tommaso, a keen naturalist and skilled biologist, specialized in a field different from biosystematics.
Distribution. Argentina, Paraguay (?).
Comparative notes. The new species chromatically differs from both M. minax and M. abstersus in the coloration of the head, which is predominantly yellow on frons and clypeus rather than totally or almost totally black. Additionally, the elytral colour pattern appears quite characteristic, with the suture generally broadly banded in black, and the presence of spots in the middle of the elytron predominantly oriented longitudinally. Moreover, elytral punctation is usually less dense than in the other species, and arranged in almost regular rows. The most evident difference, however, lies in the shape of the median lobe, where the median bulge on the ventral surface is significantly reduced compared to what is observed in the other species of the group.
Description of male. Habitus in figs 3a–b (HT). BL = 5.2–5.3 mm, BW = 3.0– 3.1 mm, PL = 1.7–1.8 mm, PW = 2.5–2.7 mm. Interocular distance 11.4–11.6 % of BL.
Head: usually black, with clypeus and lower part of frons yellow. Usually, yellow pattern extended upwards in form of two curved spots along inner border of eyes, leaving a black line in middle. At times such spots reduced to small round markings between upper lobes of eyes. Labrum light yellow as well. Surface of upper frons and vertex quite convex, head punctation sparse, moderately impressed on vertex, denser and stronger on clypeus and along inner rim of eyes. Setosity almost missing on vertex and frons but, again, thick and adpressed along lower part of inner eye margins and along median line between eyes. Mid-cranial suture usually scarcely visible. Upper lobes of eyes well separated along median lines. Ocular lines shallow, strictly adhering to ocular rim, marked by rows of small punctures. Ocular canthus rounded, scarcely setose. Antennae rather short, slender, blackish with first five antennomeres partly yellowish, 3–5 bright, subcylindrical, the subsequent ones dull, moderately flattened and more diffusedly setose.
Pronotum: black with variable yellow pattern. Usually lateral and anterior margins are yellow, as well as outer part of posterior one. Besides, a longitudinal yellow line present at center of disc, starting from anterior margin and often reaching posterior one. In this case such yellow line broadening backwards and containing small black fleck just in front of scutellum. Pronotal outline weakly transverse, regularly convex. Lateral margins narrow, regularly curved with maximum width just behind half of length. Posterolateral impression short, shallow. Surface moderately lustrous with scattered, well-impressed, often double-sized punctation, denser on sides, almost obliterated on central part of disc.
Scutellum: completely black, moderately raised. Apex truncated in a straight line or mildly rounded. Surface smooth, minutely and sparsely punctured, with few, short, whitish setae.
Elytra: elytral colour pattern remarkably variable as well. Often, elytra yellow with common, large, black stripe along suture, extending from anterior margin to elytral clivus. Black stripe, when complete, usually shortly broadened at its anterior third. Occasionally, black stripe may diminish progressively to almost disappearing towards elytral base, however, the black broadening on anterior third tends to persist in form of common rounded spot or two distinct, sometimes blurred markings. More rarely, black stripe reduced to very narrow black line along suture. Specimens with more extended dark elytral pattern, exhibit nearly rectangular or vaguely C-shaped, longitudinal black spot at middle of elytron. In some specimens, longitudinal spot merging with sutural stripe to give a pattern where dark colouration predominates over yellow (Fig. 3h). Humeral callus always spotted with black even in lighter specimens. In a single specimen (Fig. 3g), elytral dark pattern retained but faded into faint light brown design, almost not distinguished from yellow background. As a result, elytra might initially appear completely yellow. Elytral outline cylindrical with sides almost parallel. Lateral margins narrow, scarcely visible from above. Scutellar area not raised. Humeral callus scarcely prominent, not punctured. Elytral punctation moderately impressed, mostly sparse over anterior half, posteriorly arranged in almost regular rows. Intervals flat. Epipleura slightly convex, with smooth, impunctate surface.
Pygidium: usually black (but almost completely yellowish in some specimens), smooth, covered by thick, adpressed, whitish setae and sparse well-impressed punctures.
Underside: ventral surface black (sometimes part of the rear margin of the fifth abdominal ventrite yellowish), matt, covered with long, thick, adpressed, whitish setae, except shiny, scarcely setose, sparsely punctured posterior part of hypomera. Prosternal process narrow, fairly grooved at middle, with apex short triangular. Surface of prosternal process covered with long, thick, semi-erect whitish setae. Fifth abdominal ventrite with deep, heart-shaped, bald, shiny, impunctate median depression and deeply notched posterior margin.
Legs: black with yellow stripe along anterior margin of anterior femora. Median and posterior femora partly yellow as well.
Male genitalia: Median lobe of aedeagus (Fig. 4e–g) subcylindrical with apex rounded, flattened, paddleshaped in ventral and dorsal view, almost straight in lateral view. Setose depressions shifted to very lateral border of ventral surface, very sender, barely visible, marked with very few, tiny setae. Ventral surface just below apex raised in moderate, squat, roughly angulate median bulge. Endophallus very similar to that of M. minax, with no significant differences detected.
Female. BL = 5.6–6.4 mm, BW = 3.2–3.9 mm, PL = 1.8–2.1 mm, PW = 2.8–3.3 mm. Interocular distance 15.6–17.9 % of BL.
Female differs in the larger interocular distance and in the larger and stouter body. No significant differences have been noticed regarding the colour pattern.
The pit on the fifth abdominal ventrite in females is large and deep. The bottom of the pit is glabrous, matt, impunctate but covered by sparse, tiny wrinkles.The vasculum of the spermatheca (Fig. 5c) is moderately pigmented, sickle-shaped with straight, not swollen proximal lobe. The distal lobe is long, not swollen, tapered toward the apex. The ampulla is not pigmented, small, sitting just at basal apex of vasculum. The duct and the sperm gland insertions are perceptibly distinct. The duct is very long, uniform in size, slender, floppy, strictly coiled, with its insertion on the bursa copulatrix forming a rigid, twisted, well pigmented sleeve.
description: Published as part of Sassi, Davide, 2025, Revision of the Metallactus minax Suffrian, 1866 species-group (Coleoptera: Chrysomelidae: Cryptocephalinae), pp. 71-86 in Zootaxa 5583 (1) on pages 80-85, DOI: 10.11646/zootaxa.5583.1.3, http://zenodo.org/record/14798002