Mylassa monrosi, 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 : 325-328

Mylassa monrosi sp. nov.

urn:lsid:zoobank.org:act:

( Fig. 6 ; Figs. 13b ; 16g –i ; 21a–c ; 23e–f ; 27a )

Mylassa obliquata Monrós, 1949: 516 (misinterpretation).

Types. HOLOTYPE: CHILE: Los Lagos: ( BYU), ♂, body and detached abdomen glued on same card, median lobe of aedeagus glued on different card, // “ CHILE, prov. Osorno, Antillanca , 3700 ft., 10-II-1968, C.W. & L.B O’Brien ” [white label, printed] // “ Mylassa monrosi sp. nov . HOLOTYPUS D. Sassi des.” [red label, printed] //. PARATYPES (48): ARGENTINA: Chubut: ( MDPC), 3♂ 2♀, // “Argentina—Chubut Parc. Nacio. Los Alerces 700–1200m, 16.III.1974, leg. Carlo Bordon ” [white label, printed] //; ( DSPC), 1♂ 1♀, // “ Los Alerces 1100m Chubut” [white label, printed] // “ Arg. Bordón leg. 11.III.1974 ” [white label, printed] //. Neuquén: ( USNMNH), 1♂, // “ 28.XII.1951 Chapelco 1000m Terr. Neuquen l. Skhajovskoi ” [white label, printed] // “ F. Monros collection 1959” [white label, printed] //. Río Negro: ( USNMNH), 1♂ 1♀, // “RA.—Neuquen Nahuel Huapi Llao-llao I.1943 Monrós ” [white label, handwritten] // “ F. Monros collection 1959” [white label, printed] // “ Mylassa obliquata (Suffr.) F. Monrós det. 1949” [white label, partly printed] // “ Mylassa concinna (Phil.) det. I.S. Askevold 1993” [white label, partly printed] //. CHILE: Araucanía: ( DSPC), 1♀ // “Chile I-1962 Cord. Lonquimay Sierra Nevada” [white label, printed] //; ( IAPC), 1♀, // “ Malleco Prov. Parc Nac Nahuelbuta 1100 m Jan 5–8.89 Coll. C.L. Bellamy ” [white label, printed] //. Los Lagos: ( BYU & DSPC), 6♂ 7♀, same data of the holotype; ( MSNG), 1♀, // “ Chile W, Reg. X Entre Lagos 12.II.2005 W of Anticura M. Snížek lgt.” [white label, printed] // “ Museo Genova ex coll. M. Snizek acquisto 2010” [white label, printed] //; ( DSPC), 1♀, // “Chile 200m prov. Llanquihue Petrohué 25.II.1972 ” [white label, printed] //; ( USNMNH), 2♀, // Chile: “ Osorno P. N. Puyeuhe Río Anticura 31 Jan –13 Feb 78 C.M. & O.S. Flint, Jr.” [white label, printed] // “ Mylassa concinna (Philippi) det. I.S. Askevold 1993” [white label, partly printed] //; ( NMPC), 3♀, // “Chile: X. Los Lagos Region PN Puyehue, 2.0 km E of Anticura Río Colorado at Puente Arauco, 40° 40.3’S 72° 8.8’W, 465m, 8.xii.2013, Fikáček, Kment & Vondráček lgt. CH34” [white label, printed] //; ( USNMNH), 1♂ 1♀, // “Trovador 1500m 31.1.49” [white label, handwritten] // “ F. Monros collection 1959” [white label, printed] //; ( DSPC), 1♂ 2♀, // “ Chile Ayren II-1990 ” [white label, printed] //; ( SMNS), 1♂ // “ Sud-Chile A. Büttocher ” [white label, printed] // “Cryptocephal. rubronotatus Blanch. Sud-Chile ” [white label, handwritten] //; ( SMNS), 1♀ // “Sud Chile” [white label, printed] // “Cryptocephal rubronotatus Blanch. Sud-Chile ” [white label, handwritten] //; ( IAPC), 3♀, // “ CHILE, Petrohue/ Llanquihue 13.I.1980 Luis Peña” [white label, partly handwritten]; ( IAPC) , 1♂, // “ Osorno Jihron ” [white label, handwritten] // “Zool. Mus. Berlin” [white label, printed] // “ In exchange from: Zool. Mus. Berlin IS Askevold Coll’n. ” [white label, partly handwritten] // “ Mylassa obliquata (Suff.) det I. S. Askevold 1987” [white label, partly handwritten] //. Los Ríos: ( IAPC), 2♂ 1♀, // “ Valdivia Prov. 3 km W Las Lajas W La Union 650m 1.10.1989 Coll. C.L. Bellamy ” [white label, printed] //; ( IAPC), 1♀, // “ Valdivia Prov. Las Lajas (las Tables) W La Union 600m Jan. 11.1989 C.L. Bellamy ” [white label, printed] //; ( IAPC), 1♀, // “ Valdivia Prov. Parc Nac. El Azerzal [presumed transcription error; locality likely refers to Alerce Costero National Park] 900m Jan 10 1989 Coll. C.L. Bellamy ” [white label, printed] //. All paratypes also labelled: // “ Mylassa monrosi sp. nov . PARATYPUS D. Sassi des.” [red label, printed] //.

Type locality. Antillanca ( Región de Los Lagos, Chile) .

Etymology. The species is dedicated to the Hispanic-Argentinian entomologist Francisco de Asis Monrós, who extensively studied Mylassa and first studied part of these specimens but failed to recognize them as a new species.

Additional data from literature. As M. obliquata : ARGENTINA: Neuquén: Northern shore of Lake Lacar ( Monrós, 1949); Río Negro: Lake Nahuel Huapi ( Monrós, 1949).

Distribution. Argentina ( Chubut, Neuquén, Río Negro); Chile ( Araucanía, Los Lagos, Los Ríos).

Biological notes. No data available.

Diagnosis. Due to its relatively large size and elytral coloration, this species bears a strong resemblance to M. frigens , from which, however, it differs in having a more opaque and denser punctuated pronotum. Furthermore, the dorsal pilosity is rather short and appressed, whereas in M. frigens , the setae are much longer and tend to be erect. Additionally, sexual characteristics at the apex of the male’s anterior tibiae are less pronounced. Lastly, shape of the aedeagal apex is completely different. M. obliquata is also very similar, and in some cases, females of the two species may be very difficult to distinguish. However, closely spaced pronotal punctures, which render the pronotal surface opaque in M. monrosi , typically prove to be an effective diagnostic trait. Moreover, the reddish pattern on elytra is usually more developed in M. obliquata , above all along the basal margin. Regarding males, absence of the tooth-like process at the apex of the inner margin of the median tibiae, and reduction of the subapical denticle on anterior tibiae in M. monrosi , allow for easy differentiation.

Description of male. Habitus in Figs. 6a–c (HT). BL = 3.5–3.7 mm, BW = 2.1–2.2 mm, PL = 1.3–1.4 mm, PW = 2.0– 2.1 mm. Interocular distance 14.3–16.2 % of BL.

Head and labrum totally black. Vertex and frontoclypeal surface almost regularly convex, with sparse short setae and minute, close, regularly distributed punctation. Mid-cranial and frontoclypeal sutures not clearly detectable. Eyes small, scarcely bulging, only shallowly notched on inner margin with upper lobes well separated from each other. Ocular lines not detectable.Antennae long, reaching elytral apex when bent backwards, antennomeres robust, brown (1–3 sometimes slightly paler), bright, scarcely setose; antennomeres 4–10 subcylindrical, scarcely different in shape.

Pronotum totally black, regularly convex, bulging. Lateral margins narrow, not visible from above, perceptibly convergent forwards, with maximum width behind middle. Posterolateral impressions short and shallow, close to posterior margin. Pronotal surface covered with close, regularly distributed well-impressed punctation and short, appressed whitish setae. Posterior lobe almost parallelsided, narrow, rather long, slightly convex with apex truncated in straight line.

Scutellum black, triangular, not raised, very minutely punctured, surface covered with short, whitish setae.

Elytron black with oblique reddish spot at about midline, between fourth and eighth rows of punctures. Further reddish spot at apex. Sometimes additional small marking, reddish as well, close to anterior margin. Elytral outline cylindrical, rather slender, regularly convex, with sides almost parallel or slightly convergent toward apex. Lateral margins narrow, not visible from above. Scutellar area not raised. Humeral callus scarcely prominent, not punctured. Elytral surface matt, with punctures arranged in almost regular rows, well impressed on anterior half of surface, barely distinguishable towards apex. All elytral surface covered with rather short, sparse, appressed whitish setae. Sometimes pilosity arranged into nearly regular rows. Epipleura narrow, with flat or slightly concave, matt surface, marked with shallow punctures.

Pygidium black, covered by fine punctures and rather thick, whitish setae.

Ventral surface black, matt, shallowly but closely punctured, covered with long, appressed, whitish setae, except scarcely setose, shiny, not punctured posterior half of hypomera and central part of metasternum. Prosternal process wide, transverse, depressed along midline and raised at sides; sides with sharp denticle at middle; surface minutely punctured, covered with thick appressed setae; posterior margin rounded.

Legs totally black. Anterior tibiae slightly expanded and bent inwards at apex, with small subapical denticle on inner rim. Sometimes subapical denticle scarcely detectable. Apex of median tibiae slightly expanded but devoid of tooth-like process.

Abdomen in lateral view strongly concave. Fifth abdominal ventrite devoid of median depression along posterior margins. Posterior margin of fifth abdominal ventrite straight.

Median lobe of aedeagus ( Figs. 16g –i ) in ventral view terminated with short, rounded apex weakly delimited from rest of shaft. Aedeagal ventral surface smooth, with only hint of low, short, longitudinal carina. Setose depressions slender, shallow, scarcely delimited, with setae thicker on apical end. Setigerous lamellae large, triangular, bearing long, thick setae.

Female. Habitus in Figs. 6d–f . BL = 3.6–4.1 mm, BW = 2.3–2.7 mm, PL = 1.5–1.6 mm, PW = 2.2–2.4 mm. Interocular distance 16.7–17.1 % of BL.

Female differs in the stockier body, the shorter antennae and, usually, the more extended light colour pattern on elytron.

Fifth abdominal ventrite in female with shallow, rounded pit with a flat, not punctured, bright base.

The vasculum of spermatheca ( Figs. 23e–f ) is slender, hook-shaped, with proximal and distal lobes not swollen, approximately of same length. Distal lobe is slightly pigmented towards apex. Ampulla is lengthened, cylindrical. Duct insertion and sperm gland insertion fully separate, the latter sitting at proximal end of ampulla. Duct is short, coiled along its distal section while the proximal section surrounded by the rigid sleeve is about equal in length or even longer than distal one.

Remarks. In DSPC, three specimens are hosted which bear a label stating: ‘ Chile, Ayren II.1990.’ Apparently, this placename does not seem to correspond to any documented locality in Chile. If it were a typographical error and the location in question were instead Aysén, this would be of considerable interest, as it would imply an extension of the southern limit of the species’ distribution to at least the 46th parallel of south latitude. However, further reliable confirmations are needed before considering this hypothesis acceptable.

Figures

FIGURE 6. Mylassa monrosi. a–c: male, habitus in dorsal (a), lateral (b) and frontal (c) view (HT, Antillanca, Los Lagos, Chile); d–f: female, habitus in dorsal (d), lateral (e) and frontal (f) view (PT, Cord. Lonquimay Sierra Nevada, Araucanía, Chile). Images not to scale.

FIGURE 13. Pronotum. a: Mylassa rubronotata (Curicó E. of Potrero Grande, Maule, Chile); b: M. monrosi (HT, Antillanca, Los Lagos, Chile); c: M. fuliginosa (PT, Cord. Nahuelbuta Pichinahuel, Chile); d: M. flavolimbata (PT, Embalse Bullileo, Ñuble, Chile). Images not to scale.

FIGURE 16. Median lobe of the aedeagus in ventral (left), dorsoapical (center) and lateral (right) views. a–c: Mylassa pectinicornis (Ralco, Biobío, Chile); d–f: M. rubronotata (Curicó E of Potrero Grande, Maule, Chile); g–i: M. monrosi (PT, Parque Nacional Los Alerces, Chubut, Argentina). All images in the figure courtesy of Michele Zilioli (MSNM).

FIGURE 21. Median lobe of the aedeagus with everted endophallus. Mylassa monrosi (PT, Antillanca, Los Lagos, Chile), in ventral (a), dorsal (b) and lateral (c) views [scale bar = 0.8 mm]. sc1–sc4: sclerites of endophallus; sl: setigerous lamella. All images in the figure courtesy of Maurizio Bollino (Lecce).

FIGURE 23. Spermatheca. a–b: Mylassa crassicollis [scale bar = 0.5 mm]; c–d: M. frigens [scale bar = 0.4 mm]; e–f: M. monrosi [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.