Mylassa ferruginea, 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 : 338-339

Mylassa ferruginea sp. nov.

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( Figs. 7d–f ; 14d ; 25e ; 27b )

Types. HOLOTYPE: PARAGUAY: ( MNHUB), ♀, body and detached abdomen glued on same card, genitalia glued on different card, // “19 sept. Baccharis tridentata” [white label, handwritten] // “ Paraguay leg. C. Fiebrig ” [white label, printed] // “ Mylassa ferruginea sp. nov . HOLOTYPUS D. Sassi des.” [red label, printed] //.

Type locality. “ Paraguay ”

Etymology. The species name ferruginea derives from the Latin ferrugineus (‘rust-colored’), referring to the predominantly reddish hue of the dorsal colour pattern.

Distribution. Paraguay (no further locality data available).

Biological notes. No data available.

Diagnosis. This species is most easily distinguishable by its dorsal, rusty red coloration extending to the pronotum and the entire surface of the legs. The highly convex shape of the pronotum, the relatively large size, and the significantly dense dorsal covering of whitish setae somewhat resemble M. crassicollis . However, in M. ferruginea , the pronotal surface is distinctly matte (shiny in M. crassicollis ). Additionally, elytral punctures are more pronounced, and setae on elytral surface appear longer and semi-erect (appressed in M. crassicollis ).

Description of female (male unknown). Habitus in Figs. 7d–e (HT). BL = 4.3 mm, BW = 2.7 mm, PL = 1.7 mm, PW = 2.3 mm. Interocular distance 23.3 % of BL.

Head brownish, labrum yellow. Vertex and frontoclypeal surface impunctate but covered by tiny rugosity and long, thick, appressed white setae hiding almost whole surface. Mid-cranial and frontoclypeal sutures not clearly detectable. Eyes small, only shallowly notched on inner margin with upper lobes well separated from each other. Ocular lines scarcely impressed, perceptible only along upper ocular edge. Antennae missing in the only available specimen.

Pronotum rusty red with large, rhomboid, blackish patch at middle of disc. Such patch longitudinally expanded backwards to reach the posterior lobe, blackish as well. Pronotal outline strongly bulging, with lateral margins narrow, not visible from above, almost straight, fairly converging towards anterior margin so that overall outline vaguely trapezoidal, maximum width at basal margin. Posterolateral impressions long, obliquely departing from posterior margin towards sides, well impressed so that central part of disc looking particularly bulging. Pronotal surface matt, impunctate but covered with close network of tiny rugosity; along margins almost hidden by long, thick, appressed, white setae; on central part of disc setae look thinner and reddish, not hiding the underlying surface. Posterior lobe rather large, slightly convex with apex truncated in straight line.

Scutellum black, bare, triangular, not raised, densely and finely punctured and setose.

Elytron rusty red, suture and posterior part of lateral margin black; humeral callus black as well. Further longitudinal, slender, blackish stripe at middle of disc. Elytral outline cylindrical, regularly convex, with sides almost parallel, i.e. not clearly convergent toward apex. Lateral margins narrow, not visible from above. Scutellar area not raised. Humeral callus scarcely prominent, not punctured. Elytron covered with long, appressed, whitish setae, rather irregularly arranged, being less dense in proximity of scutellar area and clivus. Elytral surface with rows of punctures almost obliterated, only partly detectable, covered with network of tiny rugosity not as thick as on pronotum, so that surface looks slightly shinier.

Epipleura narrow, with weakly concave surface covered with dense whitish pilosity.

Pygidium and ventral parts hidden by coarse, appressed, white pilosity, except almost bare and shiny posterior part of hypomera and mesoepimera. Prosternal process wide, short; posterior angles broadened, bluntly triangular; posterior margin rounded; surface equally covered with coarse pilosity.

Legs completely rusty red, covered with thick, whitish pilosity.

Fifth abdominal ventrite with rather deep, rounded pit with flat, almost bald, coarsely but shallowly punctured base.

Lobes of vasculum of spermatheca ( Fig. 25e ) approximately of same length, swollen, in particular proximal one. Distal one straight, with tapered apex. Ampulla well pigmented, lengthened, tapered apically, where sperm gland insertion starts with button-like blackish swelling. Duct insertion fully separate from sperm gland insertion. Duct fine, distal section loosely coiled up; proximal section and insertion on bursa copulatrix missing.

Remarks. Morphologically, the species appears well distinguished from other members of Mylassa .Additionally, the structure of the spermatheca is unusual, with a swollen vasculum. Unfortunately, the proximal portion of the ductus was lost during preparation.

Figures

FIGURE 7. Mylassa fuliginosa. a–c: female, habitus in dorsal (a), lateral (b) and frontal (c) view (PT, Cord. Nahuelbuta Pichinahuel, Chile). Mylassa ferruginea. d–f: female, habitus in dorsal (d), lateral (e) and frontal (f) view (HT, “Paraguay”). 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 25. Spermatheca. a: Mylassa fuliginosa [scale bar = 0.4 mm]; b: M. flavolimbata [scale bar = 0.4 mm]; c: M. daccordii [scale bar = 0.4 mm]; d: Mylassa longicornis [scale bar = 0.3 mm]; e: M. ferruginea [scale bar = 0.6 mm]; f: M. mirabilis [scale bar = 0.5 mm].

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.