Mucronotus, Ruta, 2021

Ruta, Rafał, 2021, Three new genera of large marsh beetles (Coleoptera: Scirtidae) from Valdivian temperate rain forests of southern South America, Zootaxa 5048 (4), pp. 451-485 : 462-466

Genus Mucronotus gen. nov.

( Figs 4C , 10–22 )

Type species: Mucronotus velutinus ( Solier, 1849) , by present designation.

Diagnosis. Moderately sized (TL 4.8–8.3 mm), non saltatorial beetles, covered with suberect vestiture. Subantennal grooves deep, subgenal ridge without buttonhole configuration, eyes moderately protuberant. Pronotum slightly narrower than base of elytra, anterolateral angles subtriangular, protruding, posterolateral angles obtuse, rounded. Male: penis with oval pala, distinct parameroids and bifid trigonium; tegmen with wide parameres forming two projections of variable shape in apical portion. Female: ovipositor with membranous coxites, styli apical; abdominal ventrites with regular setation.

Description. Male. Body ( Fig. 10 ) oblong oval, TL 4.8–8.3 mm, moderately convex. Body yellowish brown to brownish black, covered with dense, suberect setae, head and pronotum covered with granulate punctures, remaining portions of dorsum covered with normal (not granulate) punctures.

Head moderately big, wider than long; eyes big, oval, moderately protuberant, finely facetted; tempora long, distance from posterior margin of eye to occipital ridge ca. diameter of the eye, converging basally; distance from ventral margin of eye to subgenal ridge equal to ca. 0.5× diameter of the eye; supraantennal ridges slightly elevated, joined mesally to clypeal margin; frons flat to slightly convex; subantennal groove deep, ventrally reaching subgenal ridge. Frontoclypeal suture absent; clypeus transverse, ca. 3.6× wider than long, with straight anterior margin, lateral margins converging posteriorly. Anteclypeus present, short, ca. 2× shorter than clypeus. Ventral portion of head between subgenal ridges concave, gular area convex, square, gular ridges well developed. Subgenal ridge well marked, without buttonhole configuration. Antennae filiform, reaching basal 1/3 of elytra; antennomere 1 widest, subcylindrical, without ridge on anterior margin; antennomere 2 subconical, narrower and ca. 2.5× shorter than antennomere 1; antennomere 3 very narrow, as long as antennomere 1, slightly widening apically; antennomeres 4–10 subtly widening apically, antennomere 4 slightly longer than antennomeres 5–10, which have similar length; apical antennomere slightly longer than preceding one. Labrum well visible, covered with relatively long setae, transverse, ca. 2.0× wider than long, anterior margin slightly emarginated, anterolateral angles widely rounded. Mandibles ( Fig. 12A ) symmetrical or subtly asymmetrical, ca. 2.0× longer than width at bases, abruptly curved in apical 1/4, apices unidentate, outer margin covered with long setae; inner margin of mandibles with one well developed triangular denticle and two smaller subtriangular denticles, often fused and forming subrectangular lamina; molar region without setae. Maxillary palpi ( Fig. 12C ): palpomere 1 short, subconical, 2 longest, ca. 2.0× longer than palpomere 1, subcylindrical, 3 shorter than 2, subconical, 4 fusiform, narrow, slightly shorter than 3. Galea with rounded sides, shorter than lacinia, with long, irregularly arranged setae at apex; lacinia with straight or slightly curved, strong setae. Mentum ( Fig. 12B ) transverse (W/L 1.4), subtrapezoidal. Ligula narrow at base, subtriangularly widening apically, apical margin membranous and bilobed, covered with dense setae. Labial palpomeres: palpomere 1 long, narrow, ca. 2.5× longer than wide, slightly curved; palpomere 2 wide, subconical to axe-shaped; apical palpomere arising subapically from preapical one, digitiform, slightly curved, as long as palpomere 1.

Pronotum transverse, distinctly narrower than base of elytra, ca. 2.0× wider than long; lateral carinae slightly curved, converging anteriorly; disc moderately convex; anterolateral angles subtriangular, strongly projecting; posterior angles obtuse; base bisinuate. Prosternum reduced anteriorly; prosternal process narrow, rhomboidal, with elongated posterior portion that is slightly curved ventrad, ca. 2.5–3.0× longer than wide, covered with subtle setae.

Scutellar shield small, equilaterally triangular, with slightly curved lateral margins, flat, with pointed apex; anterior margin straight. Elytra elongated, distinctly wider at base than pronotal base; humeri well marked, apices regularly rounded, each elytron with three subtly marked longitudinal carinae. Epipleura wide at base, slightly narrower than metanepisternum, regularly narrowing till apex, present till apices. Punctation of elytra irregular, not granulate, uniform, sparse, punctures separated by ca. 1.0–1.5× diameter of a puncture.

Hind wings ( Fig. 4C ) ca. 2.3× longer than wide; radial cell subtriangular; apical portion of r3 well visible, straight; rp-mp2 arcuate, forming acute angle with MP 1+2; MP 4 long, oblique, joining MP 3 and CuA+AA 1+2; anal field with well marked AP 3 and AP 4. Medial field with 3 free veins; pigmented areas in radial cell, medial, radial, central and apical fields.

Mesoventrite ( Fig. 11 ) small; anterior margin with distinct coxal rests; mesoventral process with well marked longitudinal suture; anterior portion forming narrow but deep subtriangular fossa for reception of prosternal process; mesoventral process short, ca. 1.6× longer than wide, sides subparallel to slightly converging posteriorly, apex bilobed, touching metaventrite; mesocoxae completely separated; mesanepisternum rhomboidal, wider than long, forming coxal rest for procoxa; mesepimeron smaller, impunctate, subtriangular, strongly narrowed mesally; mesocoxae triangular, slightly projecting.

Metaventrite moderately long, transverse (W/L 3.2), convex; discrimen complete; metanepisternum subtrapezoidal, ca. 2× longer than its width, slightly narrowing posteriorly. Metacoxae moderately large, strongly oblique, 3.0× wider than long, extending laterally to epipleura; metacoxal plate obliquely narrowing, absent in outermost portion.

Legs moderately long; femora slightly extending beyond elytral margin, trochanters moderately long; trochantero-femoral joint oblique; femora as long as or slightly longer than tibiae, widened in the middle of their length. Tibiae narrow, not widening towards apices, with paired carinae; metatibial spurs short, shorter than metatibial width; tarsi longer than half length of tibiae; tarsomere 1 elongated, narrow, slightly triangularly widened, as long as tarsomeres 2–4 combined; tarsomere 4 bilobed apically; apical tarsomere as long as tarsomeres 3 & 4 combined.

Abdomen ca. 1.2× longer than its width, moderately convex; ventrites 1–4 of subequal length; ventrite 5 slightly longer; ventrite 5 regularly rounded at apex. Abdominal ventrites regularly covered with setae. Genitalia ( Figs 14 , 16 , 17 , 19 , 21 ) of Microcara type, symmetrical, penis large, dorsoventrally flattened, trigonium bifid, parameroids long, as long as trigonium. Tegmen large, subrectangular, parameres narrow at bases, additional ventral process present at base of each paramere, surrounding ventral portion of penis.

Female ( Figs 10B, E, G, I ). Body moderately large (TL 5.4–7.5 mm), in some species on average slightly smaller than male, in most species covered with longer, more erect setae; pronotum transverse, more convex, with subtriangular area of dense setae in posterior portion of central part of disc; scutellar shield equilaterally triangular, elytra long, with subparallel sides and three well marked longitudinal carinae, adscutellar portion of elytra slightly depressed in some species; abdominal ventrites with regular setation; ovipositor long, branchlets absent; coxites elongate, membranous, styli apical; bursal sclerite present, with small glands opening in its anterior half ( Fig. 22A ); anterior portion of bursal sclerite connected with large gland ( Fig. 22A, B ) and smaller, strongly folded structure, presumably bursella ( Fig. 22B, D ).

Biology. Larvae possibly saproxylic ( Ruta et al. 2018). Adults collected in temperate forests of southern Chile and Argentina.

Etymology. A hybrid of Latin words mucro = sword, sword point, sharp point and pronotum, a reference to sharp, pointing anterolateral angles of pronotum. Gender masculine.

Figures

FIGURE 4. Wings.A) Argelodes magnificus sp. nov.; B) Solierodes rousseli (Solier); C) Mucronotus velutinus (Solier).Abbre- viations: AA—anterior anal vein, AP—posterior anal vein, CuA—anterior cubital vein, CuA+AA1+2—fusion of anterior cubital and anterior anal veins, MP—posterior medial vein, r3—third radial cross-vein, RA—anterior radial vein, rp-mp2—second radio-medial cross-vein, ScP—posterior subcostal vein.

FIGURE 10. Mucronotus gen. nov., dorsal view. A) M. enigmaticus sp. nov., male; B) M. enigmaticus, female; C) M. pat- agonicus sp. nov., male; D) M. schwabei (Pic), male; E) M. schwabei (Pic), female; F) M. valdivianus sp. nov., male; G) M. valdivianus sp. nov., female; H) M. velutina (Solier), male; I) M. velutina (Solier), female. Scale bar = 2.0 mm

FIGURE 11. Mucronotus gen. nov., ventral portion of head, prosternum and mesoventrite.A) M. schwabei (Pic); B) M. velutina (Solier).

FIGURE 12. Mucronotus velutinus (Solier), mouthparts. A) mandible; B) labium;C) maxilla.

FIGURE 13. Mucronotus gen. nov., pronotum. A) M. enigmaticus sp. nov., male; B) M. enigmaticus sp. nov., female; C) M. patagonicus sp. nov., male, D) M. schwabei (Pic), male, E) M. valdivianus sp. nov., male, F) M. velutinus (Solier), male.

FIGURE 14. Mucronotus enigmaticus sp. nov., male.A) terminal segments and genitalia; B) penis; C) tegmen; D) sternite VIII; E) sternite IX; F) tergite VIII; G) tergite IX. Abbreviations: bl—basal lobe (of trigonium), lp—lateral process, pm—paramere, pmd—parameroid, tgp—process of trigonium, vpl—ventral processes of tegmen. Scale bar = 0.5 mm.

FIGURE 15. Mucronotus enigmaticus sp. nov., female.A) genital tract; B) bursal sclerite.Abbreviations: bscl—bursal sclerite, bsl—bursella, gla—gland. Scale bars = 1.0 mm (A), 0.5 mm (B).

FIGURE 16. Mucronotus patagonicus sp. nov., male. A) terminal segments and genitalia; B) penis; C) tegmen; D) left para- mere, close-up; E) sternite VIII; F) sternite IX; G) tergite VIII; H) tergite IX. Scale bar = 0.5 mm.

FIGURE 17. Mucronotus schwabei (Pic), male. A) penis; B) tegmen; C) sternite VIII; D) sternite IX; E) tergite VIII; F) tergite IX. Scale bar = 0.5 mm.

FIGURE 18. Mucronotus schwabei (Pic), female. A) genital tract; B) bursal sclerite. Abbreviations: bscl—bursal sclerite, bsl—bursella, gla—gland. Scale bars = 1.0 mm (A), 0.5 mm (B).

FIGURE 19. Mucronotus valdivianus sp. nov., male. A) penis; B) tegmen; C) sternite VIII, D) sternite IX; E) tergite VIII; F) tergite IX. Scale bar = 0.5 mm.

FIGURE 20. Mucronotus valdivianus sp. nov., female. A) genital tract; B) bursal sclerite. Abbreviations: bscl—bursal sclerite, bsl—bursella, gla—gland. Scale bars = 1.0 mm (A), 0.5 mm (B).

FIGURE 21. Mucronotus velutinus (Solier), male.A) terminal segments and genitalia; B) penis; C) tegmen; D) sternite VIII; E) sternite IX; F) tergite VIII; G) tergite IX. Scale bar = 0.5 mm.

FIGURE 22. Mucronotus velutinus (Solier), female genitalia (gla—gland, bscl—bursal sclerite, bsl—bursella).A) genital tract; B) gland and bursella; C) bursal sclerite; D) bursellar membrane, close-up; E) glandular membrane, close-up. Abbreviations: bscl—bursal sclerite, bsl—bursella, cr—cuticular rings, gla—gland. Scale bars = 1.0 mm (A, B), 0.5 mm (C), figures D and E not to the scale.