Calvariomorphus, Ruta & Yoshitomi, 2022

Ruta, Rafał & Yoshitomi, Hiroyuki, 2022, Calvariomorphus-a new genus of marsh beetles (Coleoptera: Scirtidae) with remarkable elytral excitators, Zootaxa 5120 (1), pp. 65-82 : 66-69

Genus Calvariomorphus gen. nov.

( Figs 1–14 )

Type species: Calvariomorphus malayanus sp. nov., by present designation.

Diagnosis. Body small (TL<2 mm), oval; head transverse, with deep subantennal fossae, subgenal ridge without buttonhole configuration; prosternal process small, elongate, tear-shaped; mesoventral notch for reception of prosternal process subtriangular to transversely pentagonal, mesoventrite with a deep groove in anterior portion, mesoventral process short, subtriangular, distinctly notched, apex bilobed. Penis symmetrical, tegmen reduced, Ushaped, sternite IX modified. Females often with excitators in apical portion of elytra.

Description. Male. Body ( Figs 1 , 5A ) oval, TL 1.6–2.2 mm, strongly convex, light brown to brownish black, covered with whitish, suberect setae, punctation of dorsum not granulate.

Head ( Figs 2 , 5D ) small, wider than long; eyes of moderate size, not protuberant, finely facetted; tempora relatively short, distance from posterior margin of eye to occipital ridge ca. 1/5 diameter of the eye, strongly converging basally; distance from ventral margin of eye to subgenal ridge very small, eye almost touching subgenal ridge; supraantennal ridges not elevated, joined mesally to clypeal margin; frons slightly convex; subantennal fossae big and deep, ventrally reaching subgenal ridge. Frontoclypeal suture absent; clypeus transverse, ca. 4× wider than long, with straight anterior margin, lateral margins subtly converging posteriorly. Anteclypeus present, very short, shorter than clypeus. Ventral portion of head between subgenal ridges slightly concave, gular area convex, gular ridges well developed. Subgenal ridge well marked, without buttonhole configuration. Antennae filiform, covered with relatively long setae, reaching basal portion of elytra; antennomere 1 widest, subcylindrical, with sharp ridge on anterior margin; antennomere 2 subcylindrical, narrower and distinctly shorter than antennomere 1; antennomere 3 very narrow, subconical, shorter than antennomere 2; antennomere 4 long, with subparallel sides, ca. 2× longer than antennomere 3; antennomeres 5–10 slightly shorter than antennomere 3, subcylindrical; antennomere 11 slightly longer than antennomeres 5–10, subtriangular. Labrum 1.5× narrower than clypeus, transverse, ca. 1.6× wider than long, anterior margin and anterolateral angles rounded. Mandibles ( Fig. 2B, C ) slightly asymmetrical, denticle on right mandible better developed, ca. 2× longer than wide at bases, abruptly curved in apical 1/3, apices unidentate, outer margin covered with sparse setae; inner margin of mandibles with sharp ridge and subtriangular denticle; mola without spines or setae. Maxillary palpi ( Fig. 2D ): palpomere 1 subconical, 2 shorter, subcylindrical, 3 longest and widest, subconical, 4 as long as 3 but slightly narrower, subconical, pointed at apex. Galea with subparallel sides, slightly shorter than lacinia, with two fan-shaped rows of setae at apex; lacinia subtriangular, elongate, inner margin of lacinia with straight setae, setae on apical portion hooked. Mentum ( Fig. 2B, E ) only slightly wider than long, transverse (W/L = 1.2), subquadrate. Ligula narrow at base, widened apically, transversely oval, apical margin rounded, covered with setae, without membranous portion. Labial palpomeres: palpomere 1 long, narrow, sinuate, palpomere 2 wider, subconical, curved; apical wide, subconical, arising from apex of preapical one.

Pronotum small, transverse, slightly narrower than base of elytra, ca. 2.2× wider than long; lateral carinae straight, converging anteriorly; disc convex; anterior margin rounded; anterolateral angles subrectangular, not projecting; posterior angles subrectangular, well marked; base rounded. Prosternum reduced anteriorly; prosternal process narrow, elongate, tear-shaped, ca. 2.5× longer than wide, covered with delicate setae.

Scutellar shield small, equilaterally triangular, flat, with pointed apex; anterior margin straight. Elytra elongated, wider at base than base of pronotum; widest in anterior 1/3; humeri well marked, apices regularly rounded. Epipleura narrow at base, half as wide as metanepisternum, gradually narrowing, present till apices. Punctation of elytra irregular, not granulate, uniform, sparse.

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

Mesoventrite ( Fig. 5D–E ) small; anterior portion with deep grooves along anterior margin, central portion forming oval or hexagonal fossa for reception of prosternal process; mesoventral process completely separating mesocoxae, as long as wide, sides slightly converging posteriorly, apex bilobed, touching metaventrite; mesanepisternum rhomboidal, impunctate, with concave central portion, forming coxal rest for procoxa; mesepimeron small, impunctate, subtriangular, slightly narrowed mesally.

Metaventrite ( Fig. 5B–C, G ) moderately long, transverse, convex; anterior portion with spherical cuticular structures; discrimen present in posterior 1/2; metanepisternum subtrapezoidal, slightly narrowing posteriorly. Metacoxae moderately large, strongly oblique, ca. 3.7× wider than its length, extending laterally to epipleura; metacoxal plate obliquely narrowing.

Legs moderately long, tibiae with paired carinae, without modifications.

Abdomen ca. 1.1× wider than its length, convex; ventrites 1–4 of similar length; ventrite 5 slightly longer, subtriangular at apex. Ventrites 2–5 covered with regularly distributed setae, ventrite 1 with setae only in central portion, lateral portions without setation ( Fig. 7A ).

Sternite VIII absent; sternite IX U-shaped or V-shaped, apical portions of lateral arms widened in some species; tergite VIII with apodemes as long as apical plate, apical plate transverse, subrectangular to subtrapezoidal, apical margin covered with dense setae; tergite IX slightly shorter than tergite VIII, apical portion membranous, apodemes slightly longer than apical portion, diverging. Tegmen reduced, U-shaped, parameres pointed or armed with spines. Penis symmetrical, dorsoventrally flattened; trigonium elongated, subrectangular, pointed at apex, shorter to slightly longer than parameroids, parameroids long and narrow, often subrectangular, sometimes with spines on apical margin, apices rounded.

Female. TL 1.7–2.2 mm. Apical portion of elytra often with excitators (sensu Ruta 2008), presumably secretory structures connected with exocrine glands ( Fig. 4 ). Hind wings functional, fully developed. Setation of abdominal ventrite 1 present along posterior margin of ventrite ( Fig. 7B ). Sternite VIII ( Fig. 9 ) elongate oval, apex with sparse setae. Tergite VIII very long; apical portion subtrapezoidal, with sparse setation on apical margin; apodemes long, several times longer than apical portion. Ovipositor long; branchlets present; gonocoxites narrow, membranous, gonostyli arising apically, each with two tufts of setae at apex. Bursa membranous, with variable sclerites present; bursella small, spherical, accessory gland sometimes with sclerites near to its opening.

Biology. Unknown.

Etymology. Combination of the name Calvarium Pic and the New Latin ending – morphus meaning having the shape of Calvarium . Reference to the similarity to the genus Calvarium Pic. Gender : masculine.

Figures

FIGURE 1. Calvariomorphus gen. nov., dorsal view (with the exception of H). A) C. malayanus sp. nov., male, B) same, fe- male, C) C. palauensis sp. nov., male, D) same, female, E) C. sakaii sp. nov., male, F) same, female, G) C. sp. (Nicobar Islands), H) same, semilateral view. Scale bars = 0.5 mm.

FIGURE 2. Calvariomorphus gen. nov., morphology of head. A) C. palauensis sp. nov., head, ventral view, B), same, close-up of mouthparts, C) C. malayanus sp. nov., mandible, D) same, maxilla, E) same, labrum.

FIGURE 3. Calvariomorphus malayanus sp. nov., hind wing.Abbreviations: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 4. Calvariomorphus gen. nov., excitators. A) C. malayanus sp. nov., apex of elytron, areas with micropores marked with arrows, B) same, close-up, C) C. palauensis sp. nov., apices of elytra, caudal view, D) same, close-up, E) C. sp. (Nicobar Islands), apices of elytra, semilateral view, F) same, caudal view, G) same, close-up.

FIGURE 5. Calvariomorphus gen. nov., dorsal (A) and ventral (B–G) view. A) C. malayanus sp. nov., dorsal view, B) same, ventral view, C) C. sakaii sp. nov., D) same, close-up of head and mesoventrite, E) C. malayanus sp. nov., close-up of mesoven- trite, F) C. palauensis sp. nov., meso- and metaventrite, G) C. sakaii sp. nov., meso- and metaventrite.

FIGURE 6. Calvariomorphus peterseni (Klausnitzer), comb. nov., holotype, ventral view.A) head, ventral view, B) same, head and ventral portion of thorax, ventral view.

FIGURE 7. Calvariomorphus gen. nov., abdomen. A) C. malayanus sp. nov., male, B) C. sakaii sp. nov., female, C) same, close-up of ventrite 4.

FIGURE 8. Calvariomorphus malayanus sp. nov., male genitalia, specimen from Kuala Lumpur (A–D) and Singapore (E). A) penis, B) tegmen, C) tergite VIII, D) tergite IX and sternite IX, E) terminal sclerites and aedeagus. Scale bars = 0.25 mm.

FIGURE 9. Calvariomorphus malayanus sp. nov., female genitalia. A) genital tract, B) coxites, C) bursal sclerite. Scale bar (A) = 0.5 mm.

FIGURE 10. Calvariomorphus palauensis sp. nov., male genitalia. A) penis, B) tegmen, C) sternite IX, D) tergite VIII, E) tergite IX. Scale bar = 0.25 mm.

FIGURE 11. Calvariomorphus palauensis sp. nov., female genitalia.A) genital tract, B) bursella and bursal sclerite, C) sclerites of accessory gland. Abbreviations: bscl—bursal sclerite, bsl—bursella, gla—accessory gland. Scale bar = 0.5 mm.

FIGURE 12. Calvariomorphus peterseni (Klausnitzer), comb. nov., holotype, male genitalia. A) penis, B) tegmen, C) sternite IX, D) tergite IX. Scale bar = 0.25 mm.

FIGURE 13. Calvariomorphus sakaii sp. nov., male genitalia. A) penis, B) tegmen, C) sternite IX and tergite IX, D) tergite VIII. Scale bar = 0.25 mm.

FIGURE 14. Calvariomorphus sakaii sp. nov., female genitalia. A) genital tract, B) coxites, C) bursal sclerite. Scale bar = 0.5 mm (A, C), 0.25 mm (B).