Mylassa postmediana, Sassi, 2025

Sassi, Davide, 2025, Taxonomic revision of the South American genus Mylassa Stål, 1867 (Coleoptera: Chrysomelidae: Cryptocephalinae) with the description of eight new species, Zootaxa 5683 (3), pp. 301-359 : 335-337

Mylassa postmediana sp. nov.

urn:lsid:zoobank.org:act:

( Figs. 10a–c ; 14b ; 17g –i ; 27c )

Types. HOLOTYPE: CHILE: Valparaíso: ( BYU), ♂, body and detached abdomen glued on same card, median lobe of aedeagus glued on different card, // “CHILE, P. Valparaíso, Algarrobo, 31-XII-1967, C.W. & L.B. O’Brien ” [white label, handwritten] // “ Mylassa postmediana sp. nov . HOLOTYPUS D. Sassi des.” [red label, printed] //. PARATYPES: ( BYU & DSPC), 3 ♂, same data of the holotype, // “ Mylassa postmediana sp. nov . PARATYPUS D. Sassi des.” [red label, printed] //.

Type locality. Algarrobo ( Provincia de San Antonio, Región de Valparaíso, Chile) .

Etymology. The species name postmediana derives from the Latin post (‘behind’) and medianus (‘middle’), referring to the yellow elytral pattern, which is limited to the posterior half of the elytra.

Distribution. Chile ( Valparaíso).

Biological notes. No data available.

Diagnosis. Among small-sized species characterized by black elytral coloration with two (lateral-median and apical) yellow spots (including Mylassa flavolimbata , M. longicornis , and M. daccordii , besides the present one), M. postmediana is easily distinguished by shape of the median elytral spot, which is elongated, slender, and distinctly transverse. Additionally, the prominently bulging pronotum, very fine and almost obliterated elytral punctation, and apparent, dense pilosity on elytron are highly characteristic features of M. postmediana , which are almost absent in other species listed above.

Description of male. Habitus in Figs. 10a–b (PT). BL = 3.1–3.3 mm, BW = 1.9–2.0 mm, PL = 1.2–1.3 mm, PW = 1.8–1.9 mm. Interocular distance 18.2–19.4 % of BL.

Head totally black. Vertex and frontoclypeal surface quite shiny, almost bare, covered with fine, regularly distributed punctation; mid-cranial and frontoclypeal sutures not clearly detectable; sometimes a linear or oval impression at middle of frons. Eyes small, scarcely bulging, only shallowly notched on inner margin with upper lobes well separated from each other. Ocular lines scarcely impressed, barely visible. Antennae uniformly dark brown, almost reaching elytral clivus when bent backwards, antennomeres 4–10 short, slightly flattened, scarcely different from each other in length and shape.

Pronotum totally black, regularly convex, bulging. Lateral margins narrow, not visible from above, mildly and regularly arched, maximum width about at basal margin. Posterolateral impressions weak, short, scarcely departing from posterior margin towards sides. Pronotal surface covered with close, regularly distributed, very fine punctation and sparse, recumbent, short setae, thicker along lateral and posterior margins. Posterior lobe large, slightly convex with apex truncated in straight line.

Scutellum black, triangular, pointed, not raised, bare, rather coarsely punctured.

Elytron black with crosswise, linear yellow band just behind middle, extended from lateral margin up to about first row of punctures (i.e. not reaching suture); further crescent, yellow spot at apex. Elytral outline cylindrical, regularly convex, with sides parallel, i.e. not convergent toward apex. Lateral margins narrow, not visible from above. Scutellar area not raised. Humeral callus scarcely prominent, not punctured. Elytral surface, covered with scattered, short, whitish, recumbent setae and very fine punctation, arranged in regular rows, barely perceptible as surface covered by fine but thick roughness. Epipleura narrow, with weakly concave, minutely punctured surface.

Pygidium black, matt, covered by fine punctures and short, appressed setae.

Ventral surface black, matt, finely and densely punctured, with short, appressed setae, except scarcely setose, shiny posterior part of hypomera. Prosternal process wide, short, roughly squared; sides with sharp denticle at middle; surface with scattered punctured and scarce, short setae; posterior margin almost straight.

Legs completely black. Anterior tibiae expanded and bent inwards at apex, with small, sharp subapical denticle on inner rim. Apex of median tibiae enlarged, with robust, blunt, subapical tooth-like process on inner side.

Fifth abdominal ventrite devoid of perceptible median depression along posterior margins. Posterior margin of fifth abdominal ventrite straight.

Median lobe of aedeagus ( Figs. 17g –i ) short, squat. Ventral surface strongly concave with short, sharp median carina. Shaft terminated with rounded apical edge.Setose depressions slender, shallow, scarcely delimited. Setigerous lamellae large, triangular with long apical setae.

Female. Unknown.

Figures

FIGURE 10. Mylassa postmediana. a–c: male, habitus in dorsal (a), lateral (b) and frontal (c) view (PT, Algarrobo, Valparaíso, Chile). Mylassa longicornis. d–f: male, habitus in dorsal (d), lateral (e) and frontal (f) view (PT, Parque Nacional La Campana, Valparaíso, Chile); g–h: female, habitus in dorsal (g) and frontal (h) view (PT, Curico E of Potrero Grande, Maule, Chile). Images not to scale.

FIGURE 14. Pronotum. a: Mylassa daccordii (PT, Cord. Lonquimay Sierra Nevada, Araucanía, Chile); b: M. postmediana (PT, Algarrobo, Valparaíso, Chile); c: M. longicornis (PT, Parque Nacional La Campana, Valparaíso, Chile); d: M. ferruginea (HT, “Paraguay”); e: M. mirabilis (PT, El Carmen, Ñuble, Chile). Images not to scale.

FIGURE 17. Median lobe of the aedeagus in ventral (left), dorsoapical (center) and lateral (right) views. a–c: Mylassa flavolimbata (PT, Embalse Bullileo, Ñuble, Chile); d–f: M. daccordii (PT, Lonquimay, Araucanía Chile); g–i: M. postmediana (HT, Algarrobo, Valparaíso, Chile). All images in the figure courtesy of Michele Zilioli (MSNM).

FIGURE 27. Distribution maps. a: Mylassa monrosi; b: M. fuliginosa (circle), M. longicornis (stars), M. ferruginea (large star); c: M. mirabilis (circles), M. postmediana (star); d: M. flavolimbata (circles), M. daccordii (stars). Large star in Fig. 27b (M. ferruginea): available data indicate the presence in Paraguay, but without precise locality information.