Polyodontotrochus, González-Mozo & Mckamey, 2024

González-Mozo, Laura & Mckamey, Stuart H., 2024, A new genus and four new species of Darnini (Hemiptera: Membracidae) from South America, Zootaxa 5415 (1), pp. 169-180 : 170-171

Polyodontotrochus , new genus

Type species: Polyodontotrochus elevatus , n. sp.

Diagnosis. Head subquadrate; pronotum with large suprahumeral horns projected anterolaterally or dorsolaterally, with truncate apices; inner sides of metathoracic trochanters with apposed, studded, flattened plates ( Fig. 2 ); metathoracic tibiae with cucullate setal rows II and III incomplete, I missing.

Description. Color. Various shades of gray and brown; with white waxy substance on pronotal lateral lobe and proepimeron. Sculpture. Vertex with setae, without ventrolateral punctate regions; pronotum strongly punctate with numerous setae.

Head. Subquadrate, coronal suture indistinctly delimited on vertex in anterior view, dorsal and ventral margins not parallel, dorsal margin extended in mid 2/3rds ( Figs. 7–10 ), vertically oriented, wider than high; supraantennal margins straight ( Figs. 8, 10 ) or weakly convex ( Figs. 7, 9 ), slightly overlapping clypeus; ocelli oblong, dorsally divergent.

Thorax. Pronotum. Mostly covering forewing in repose (not covering costal or radial cells), with large suprahumeral horns, postocular lobe wide but undeveloped (not carinate), dorsal carina distinctly raised throughout, lateral longitudinal carinae present or absent, posteriorly with subtriangular apex and ventrally hollow, without air pocket, apex with single point, highest point of pronotum, excluding suprahumeral horns, behind humeral angles. Forewing. Costal margin curving to forewing apex, apical limbus beginning at vein R 1, costal cell mostly sclerotized and punctate, vein R branched, s crossvein present or absent, with 1 or 2 m-cu crossveins, veins M 3 and M 4 fused until marginal vein, M and Cu veins strongly divergent distally, forewing at rest at least half-concealed by pronotum and not quite attaining pronotal apex ( Fig. 18 ). Legs. Mesothoracic trochanters with 2–5 strongly sclerotized studs; mesothoracic femora with irregular row of ventral, strongly sclerotized studs and with apical, anterior lobe small (extending ventrally in length less than apical width); mesothoracic tibia with 2 complete ventral rows of strongly sclerotized studs; metathoracic trochanters with inner face flat, platelike, bearing 14–17 black, strongly sclerotized short studs scattered throughout ( Figs. 2, 4, 5 ); metathoracic femora ventrally with 1–5 strongly sclerotized studs present in only basal 1/4, but not in single row, 1–3 cucullate setae present ( Fig. 6 ); metathoracic tibia row I absent; row II present as single row of cucullate setae but incomplete, with only 2–5 present, spinelike; row III complete in single row for entire length; first tarsomere lacking cucullate setae on plantar surface.

Abdomen. Terga without pits, fossae, or digitate processes; pygofer without dorsal carina ( Figs. 19 , 25 ); slightly narrowed distally; subgenital plate fused for about ½ length, appearing narrowly and deeply emarginate in distal half ( Figs. 20 , 26 , 30 ); lateral plate projected dorsally distally acuminate, not fused with pygofer ( Figs. 19 , 25 , 31 ); aedeagus variable among species, in anterior view U-shaped ( Figs. 21 , 32 ), posterior shaft with minute raised ridges oriented horizontally or vertically on distoanterior surface ( Figs. 23 , 28 , 34, 36 ); style simple with recurved acute apex ( Figs. 22 , 32 ); anal segments (X, XI) sclerotized with many short setae.

Dimensions of males (mm). Length 3.5–9.2, maximum width (across suprahumeral horns) 3.1–6.0, height above humeral angles 0.9–1.7, ratio of length to width 1.2–2.2.

Female unknown.

Distribution. Neotropical: South America.

Etymology. Formed from Greek: πολύς (many) + ὀδούς, ὀδόντος (tooth) + τροχός (wheel, runner)—the first part of τροχαντήρ (trochanter)—masculine, in reference to the diagnostic condition of the metathoracic trochanther.

Discussion. Deitz (1975) included in the tribal diagnosis of Darnini the presence of cucullate setae on the ventral side of pro- and mesothoracic femora, which Dietrich et al. (2001) and Roy et al. (2007) found, in their phylogenetic analyses based on morphology, to be a synapomorphy supporting the monophyly of the tribe. Cucullate setae (CS) are modified trichoid sensilla, which consist of a cuticular projected socket, the base of which is usually smooth without punctations, with parallel longitudinal ridges distally, and a trichoid sensillum articulated within the socket. CS are highly variable in size and shape among Darnini genera. In Polyodontotrochus , we found two structures: CS and studs. CS scattered on the base of the femora, cuticular socket and associated sensillum slender with a slightly curved apex with lengths between 30–34 µm ( Fig. 6 ); here we use the word “ stud” to refer to structures found on the femora and the trochanter in which the cuticular projection is studlike as in the CS but without an associated trichoid sensillum ( Fig. 5 ). Both structures have the same studlike cuticular projection, but we refrain from referring to them as cucullate setae due to the lack of sensilla.

The function of the apposed, studded metathoracic trochanters in Polyodontotrochus are unknown, but perhaps a clue is found in the planthopper nymphs (but not adults) of Issus coleoptratus (Fabricius) ( Hemiptera : Fulgoroidea: Issidae ). This species has its metathoracic trochanters bearing apposed cogs that fit into each other, like gears, which ensures that both hind legs propel the insect with the same angular velocities without yaw rotation ( Burrows and Sutton 2013). A similar phenomenon may be also happening elsewhere in the treehopper subfamily Darninae , which is the only membracid taxon with genera having highly modified metathoracic trochanters. Though all less precise than those of the aforementioned planthopper, in Darninae these structures are present only in the adults. Procyrta Stål (Procyrtini) species bear a ring of large, irregular but sharp spines around the inner faces of their trochanters. Almost all Cymbomorpha Stål (Cymbomorphini) species have trochanters each bearing a single very stout spine apposing each other. Irregularly placed, un-apposed studs are present on the rounded mesothoracic trochanters of some “raindrop” Darnini (SHM unpubl.). The new genus described here is the first occurrence in the tribe Darnini with apposed trochanteral processes and the first in Membracidae with apposed trochanteral studs. If the function of these trochanter modifications is similar to that of the planthopper, these apposing structures among Darninae may help to synchronize the hind legs when jumping.

In any case, the presence of the uniquely modified trochanters in the four new species described here, in combination with metathoracic tibial differences compared to other Darnini and Membracidae in general, is deemed sufficient to establish a new genus. Females of the new genus are unknown and may differ from males in pronotal form, chaetotaxy, or both.

In some membracids, the presence of abdominal fossae or digitate processes are indicators of scoli in nymphs (e. g., see Deitz 1975 Fig. 3a ); the absence of these suggests that the nymphs of Polyodontotrochus probably lack scoli. The male terminalia are fairly uniform across the genus and therefore of little value for identification, while the pronotal structures are clear and distinct among species.

The natural history of Polyodontotrochus is unknown. According to label information, species are found in lower elevations, between 58–410 m. altitude. The distribution of the genus is restricted to the neotropics in Brazil, Ecuador, and French Guiana.

Figures

FIGURES 1–6. (1) Polyodontotrochus auriculatus forewing; (2) P. inpa Metathoracic leg; (3) P. elevatus metathoracic tibia; (4–6) P. auriculatus; (4) metathoracic trochanter studs; (5–6) SEM of metathoracic leg: (5) metathoracic trochanter ventral view showing studs; (6) metathoracic femur ventral view showing cucullate setae and studs. Abbreviation: C: Costal vein; CS: cucullate setae; Cu: Cubital vein; M: Medial vein; R: Radial vein.

FIGURES 7–10. Anterior views. (7) P. auriculatus; (8) P. elevatus; (9) P. inpa; (10) P. extentapalaestrus.

FIGURES 15–18. Lateral views. (15) P. auriculatus; (16) P. elevatus; (17) P. inpa; (18) P. extentapalaestrus.

FIGURES 19–24. Male genitalia P. auriculatus. (19) Pygofer, lateral plate and subgenital plate lateral view; (20) Subgenital plate; (21) Aedeagus anterior view; (22) Style posterior view; (23) Aedeagus lateral view; (24) Detail, aedeagus scalelike ridges.

FIGURES 25–28. Male genitalia P. elevatus.(25) lateral plate and subgenital plate; (26) subgenital plate; (27) aedeagus anterior view; (28) Style and aedeagus lateral view.

FIGURES 29–37. Male genitalia of P. extentapalaestrus and P. inpa. (29–34) P. extentapalaestrus; (29) Abdominal tergum VIII and pygofer, dorsal view; (30) subgenital plate, ventral view; (31) dissected pygofer, lateral view (anal segments pushed ventrally after dissection); (32) aedeagus and styles, anterior view; (33) Detail, aedeagus scalelike ridges; (34) aedeagus and styles, lateral view. (35–37) P. inpa; (35) aedeagus, anterior view; (36) aedeagus, lateral view; (37) Detail, aedeagus scalelike ridges.