Megamelus delticus Remes Lenicov & Mariani, 2025

Megamelus delticus Remes Lenicov & Mariani sp. nov.

Figs 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3

Type material.

Holotype male (brachypter): Argentina • Buenos Aires, Otamendi , 08 - VI- 2022, on Eryngium sp. , Salinas-Sosa cols . Paratypes • same data as holotype, 7 male brachypters, 6 female brachypters ( MLP) .

Other material.

Argentina • 6 male brachypters, 6 female brachypters, Buenos Aires, Otamendi, 08 - VI- 2022, on Eryngium sp. , Salinas-Sosa cols. ( MLP) • 1 male brachypters, 3 female brachypters, Buenos Aires, Dique Lujan, 19 - VII- 2023, on Eryngium sp. , Salinas-Sosa cols. ( MLP) .

Type locality.

Argentina, Buenos Aires: Otamendi, Campana, 34.1818 S, 58.8706 W, forested river margin, on Eryngium sp. , 8 August 2022.

Diagnosis.

Brachypter. The salient features of this new species include the following: dorsally overall dull dark brown color, with pale mottles on apex vertex, front disc, and a pale yellow stripe on frontoclypeal suture extending towards the base of gena. Body broadly depressed and distinctively wide at abdomen. Vertex broad, subquadrate, apical margin broadly rounded, with submedian carina forking dorsally near anterior margin of eyes, carinal branches diverging widely to meet anteriorly just below fastigium which is angled when viewed laterally. Eyes reduced, reddish, slightly emarginate below, barely visible in ventral view. Frons subcircular, short, about as long as wide, with lateral carinae bowed outward, converging both ventrally and dorsally; metatibial spur short and narrow, bearing eight or nine black-tipped sharp teeth on trailing margin. Male terminalia: pygofer short, with small sized outer lobes, inner lobes subtriangular in outline, with broad concavity between them; aedeagus short, bearing dorso-apical horseshoe-like process; anal segments short and wide, unarmed.

Description.

Brachypterous male (Figs 1 A, B, D, E View Figure 1 , 2 A – E View Figure 2 ). Color (Fig. 1 View Figure 1 ) dull dark brown, with some pale marks. Reddish eyes. Vertex pale along posterior margin, median and Y-shaped carinae, with small yellowish spots on apex between submedian and lateral carina and also between lateral carina and eyes. Frons with continuous row of ~ 10 symmetrical pale dots paralleling median and lateral carinae, and transversal whitish stripe on frontoclypeal suture extending towards the base of gena. Clypeus castaneous on disc, rostrum yellowish. Antennal segments castaneous, slightly pale on anterior surface. Pronotum with pale transversal row of small spots on anterior margin between lateral carinae and several smaller spots on central disc near posterior margin; mesonotum disc with pale longitudinal spots between lateral carinae and some small spots on posterior margin. Tegmen uniformly pale brown. Legs yellowish, darker on base and apex of pro and mesocoxae, annular dark brown stripes near the base and apex of pro- and mesotibiae, apex of pro- and mesofemur, dorsal metafemur, and two annular stripes on metatibiae, one near base and the other on base of apical spines, on dorsal surface of spurs, and base of first tarsomere and apex of third. Abdomen dark brown in dorsal view, with longitudinal bilateral narrow pale stripes on tergites III – VII and ventrally on posterior margins of sternites IV – VII, and laterally around wax pores; anal segment paler, darker on apical margin as well as on anal style.

Structure. Body strongly dorsoventrally flattened, suboval in outline. Head narrower than pronotum. Vertex in dorsal view almost as long as wide, rather quadrate, broadly rounded on anterior margin; basal compartment occupying approximately more than basal half of vertex. Median carina present, forked near anterior margin of eyes, arms of fork diverging strongly (angle 170 °) to meet submedian frontal carinae. Submedian frontal carinae arising from the lightly foliate lateral carinae at level of middle of eyes, meeting anteriorly just at the fastigium (Fig. 1 A View Figure 1 ). In lateral view, head projected downwards in front of the eye, fastigium angled (Fig. 1 E View Figure 1 ). Frons subcircular, about as long as wide, and as long as clypeus; carinae of frons distinct, evanescent toward apex, lateral carinae bowed outward, converging both ventrally and dorsally; frons widest at antenna level. Frontoclypeal suture ventrally curved. Clypeus sub-triangular with carinae evident, the laterals continuing with genal carina. Rostrum reaching metacoxae, slightly shorter than frons plus clypeus, subapical segment longer than the apical one (1.3: 1). Compound eyes, very reduced, lower margin only slightly incised, barely visible in ventral view. Antennae short, first segment as long as wide, second segment 2 × the first, 2 × longer than wide (Fig. 1 A, B View Figure 1 ). Pronotum with conspicuous carinae, the laterals divergent, reaching hind margin and ending slightly convex. Mesonotal disc almost as long as pronotum (1.2: 1), carinae conspicuous, lateral ones slightly divergent apically reaching hind margin (Fig. 1 A View Figure 1 ). Tegmen coriaceous, subquadrate, posterior margin subtruncated to slightly rounded, reaching 4 th segment; veins distinct (Fig. 1 A View Figure 1 ). Metatibial spur leaf-like, short, narrow apically and concave ventrally, bearing eight or nine black-tipped sharp teeth on trailing margin, almost as long as first segment of metatarsi at notch; first hind tarsomere longer than second plus third (1.7: 1) (Fig. 1 D View Figure 1 ). Abdomen broadest across segment V, decreasing in width towards apex (Fig. 1 A View Figure 1 ).

Terminalia. Pygofer trapezoidal, with laterodorsal margin slightly truncate, not projected caudad; ventrally ~ 2 × longer than dorsally; dorsally with shallow concave anal margination (Fig. 2 A, B View Figure 2 ); outer lobes small-sized and rounded, slightly enfolding lateral area of pygofer, in ventral view occupying half the length of pygofer, inner lobes subtriangular in outline, broadly concave between them and with narrow notch between inner and outer lobes, partially closing ventral foramen (Fig. 2 A, B View Figure 2 ); diaphragm fairly long, regularly narrowed toward middle line and caudally produced in short conical process. Aedeagus short, length-wide ratio: 2.2: 1, regularly tubular and caudally downwardly directed, bearing an apical process projected on dorsal surface to left of phallotreme; this process is forked near base in two long and divergent semi-circularly curved spines (horse-shoe outline), in lateral view extending beyond genital styles (in repose); phallotreme large, near apex on dorsal surface to the right (Fig. 2 D View Figure 2 ). Suspensorium sclerotized, strap-like, very short, half of aedeagus length (Fig. 2 D View Figure 2 ). Genital styles (parameres) straight and flattened, widest and divergent in apical 1 / 3, apices truncate and enlarged, with sharp conical process on inner angle, widely expanded and rounded on outer angle, apex reaching dorsal margin of diaphragm at rest (Fig. 2 E View Figure 2 ). Anal segment broad, collar-like, closely embraced by pygofer, without processes (Fig. 2 C View Figure 2 ); anal style short (Fig. 2 C View Figure 2 ).

Measurements (n = 3). L., 2.6; b. w., 0.75; M. b. w. at abdominal segment V, 1; t. l., 0.4; v. l., 0.4; v. w., 0.5; f. l., 0.4; M. f. w., 0.4; m. f. w., 0.25; a. l. I, 0.15; a. l. II, 0.2; p. l., 0.3; m. l., 0.4; mti. l., 0.8; mta. l., 0.7; mta. Il., 0.4; s. l., 0.4; t. n., 9.

Macropter unknown.

Brachypterous female (Figs 1 C, F View Figure 1 , 2 F – H View Figure 2 ). Color. Body coloration pattern and structure similar to male; ovipositor brown with valvifer pale on inner margin; gonapophysis rather pale apically.

Terminalia. Ovipositor short, reaching anal segment at base (Fig. 2 F View Figure 2 ). Valvifer VIII regularly broad, slightly excavated on inner margin near base, with inconspicuous basal projection; separate in repose in ventral view. Gonapophysis VIII wide at base, ventrally projected between valvifers. Gonapophysis IX slightly curved, bearing numerous strong rounded teeth (~ 35) on dorsal margin on> 1 / 2 of its length, a few teeth smaller distally; with three or four ventral teeth (Fig. 2 G, H View Figure 2 ).

Measurements (n = 3). L., 3; b. w., 0.83; M. b. w. at abdominal segment V, 1.265; t. l., 0.4; v. l., 0.35; v. w., 0.5; f. l., 0.4; M. f. w., 0.4; m. f. w., 0.25; a. l. I, 0.15; a. l. II, 0.2; p. l., 0.3; m. l., 0.4; mti. l., 0.85; mta. l, 0.75; mta. Il., 0.5; s. l., 0.4; t. n., 9–10.

Macropter unknown.

Etymology.

The specific name comes from the Greek letter delta (Δ), which was used to refer to the triangle of fertile land that the Nile forms at its mouth (Nile Delta) and by extension, to other river deltas. In this case, the name refers to the geographical distribution of the species, which is restricted to the region of the Paraná River Delta.

Distribution.

Argentina: Buenos Aires Province (Fig. 3 A View Figure 3 , Suppl. material 2).

Host plant.

Eryngium sp. ( Apiaceae ).

Ecology.

This planthopper was recorded in Otamendi and Dique Lujan, Paraná River Delta, in Buenos Aires Province ( Argentina). It was only collected on Eryngium sp. , a plant growing on the higher areas of river banks, where it is protected from periodical floods (Fig. 3 B View Figure 3 ). Large numbers of nymphs and adults were found in the center of the plant mat (Fig. 3 C View Figure 3 ), where leaves tend to accumulate water. The specimens collected had an abundant serous secretion covering their bodies, probably to repel the accumulated water. It is worth noting that M. delticus and M. nigrifasciatus were both sought after during our campaigns in search of Megamelus sp. and were only found in the same restricted geographical region, which suggests two possible cases of endemism.

Remarks.

This new species is easily distinguished from all the other Megamelus species by the broadly depressed body with a broad, sub quadrate vertex, large basal compartment, fastigium angled when viewed laterally, short and subcircular frons, small compound eyes, and the male pygofer slightly enfolded by the small sized outer lobes and the aedeagus ending in a horseshoe-like bifurcation. The dull dark brown coloration with pale dots and a transversal white stripe on the face, are also distinctive. Among the South American species, M. delticus and M. nigrifasciatus share the flat frons with convex lateral margins, the short and narrow spur with a few sharp teeth, brachypterism as the only wing form, and the short gonapophysis in females. Moreover, these species share their host plant ( Eryngium sp. ), which suggests that these morphological traits are likely adaptations to their ecological niche.