Spelaeodelphax nexus Santos & Asche sp. nov. Figs 2 E, F, 3 A – C, 4 A – C, 5 A – G, 6 A – D, 7 A – D, 8 A – P, 9 A – F, 10 A – F, 11 A – D, 12 A – D Type material. Holotype. • Male, Brazil, Bahia state, Carinhanha municipality, Lapa dos peixes I cave (UTM 13°48'55.6"S, 43°57'17.2"W, 23 K), 07. ix. 2023 (ISLA 126058) (Fig. 1). Holotype condition: Holotype condition: Not dissected, stored in individual vials in 70 % ethanol. Paratypes. • Same data as holotype except for 1 ♂ dissected, stored in individual vials in 70 % ethanol (ISLA 126059) (only male genitalia), 1 ♀ (ISLA 126061) 4 nymph (ISLA 126062), and 04. vi. 2024, 1 ♂ (ISLA 126062), 1 ♂ (ISLA 126063), 1 ♂ (ISLA 126065), 1 ♂ (ISLA 126066), 1 ♂ (ISLA 126067) (dissected), 1 ♂ (ISLA 126068), 1 ♂ (ISLA 126069), 1 ♀ (ISLA 125912), 1 ♂ (ISLA 125911) (SEM). Description. Adults. Figs 2 E, F, 3 A – C, 4 A – C, 5 A – G, 6 A – D, 7 A – D, 8 A – P. Diagnosis. Habitus. Small, light-colored and strongly troglomorphic delphacid devoid of compound eyes and ocelli, tegmina strongly reduced in length without recognizable venation, hind wings reduced to narrow pads. Configuration of male and female genitalia as described for the genus. For details of male genitalia see below. Coloration (preserved specimen). As in Figs 3, 4, predominantly deep yellow (85) on head, thorax, abdomen and genitalia, some areas in pale yellow (89) principally legs, head laterally (gena) and spaces between segments, especially of the abdomen. Body length. Male. 1.6–1.8 mm (n = 7) (Fig. 3); Female. 1.9–2.0 mm (n = 2) (Fig. 4). Configuration, shape and proportions of head, thorax and female terminalia as proposed for the genus. Some figures and measurements are provided here. Head. Vertex (Figs 3 A, 5 A, 6 A): width (0.20) length (0.04). Frons (Figs 3 B, 5 B, 6 B, C): width (0.39) length (0.38). Antennae (Fig. 5 E): Pedicel width (0.09) length (0.13). Thorax. Pronotum (Figs 3 A, C, 5 A, C). Mesonotum (Figs 3 A, C, 5 A, C): width (0.54) length (0.30). Tegmina (forewings) (Fig. 5 F, G): length (0.57). Hind legs (Figs 3 B, C, 5 D): length (0.91). Male genitalia. Pygofer (Fig. 8 A – D, G, H) bilaterally symmetrical; with caudal margin irregularly convex without lateral processes; in lateral view with irregular caudal margin, without lateral processes; dorsal margin slightly convex / irregular; in ventral view, margins in W-shaped with small triangular ventromedial process; in caudal view rounded, armature of diaphragm weakly sclerotized wider than tall; opening to inner chamber rounded, opening for gonostyli ovoid small approx. 3.0 times smaller than opening to inner chamber. Anal segment (Fig. 8 A – D, I – J) with paired lobes slightly asymmetrical, left lobe slightly larger than right one; in caudal view margin between lobes deeply concave; epiproct and paraproct rather small. Gonostyles (Fig. 1 A – C, E, F) short and slender, in lateral view pointing dorsocaudad with tip slightly surpassing laterocaudal margin of pygofer, widest in basal two thirds, with median margins opposed and close to each other, ventral and dorsal margins slightly sinuate; in distal third narrowing, forming a pair of pincers with keyhole-shaped opening between styles. Aedeagus (Fig. 8 K – N) tubular, asymmetrical; shaft with four spines: a rigid spine arising right laterally near base (long, tubular, compressed ventrally, curved and directed towards apex of shaft), 2 rigid spines at about midlength on left and right side (both compressed, triangular, one short, the other slightly longer), and a movable sinuate spine arising ventrally near apex (in repose directed basally). Flagellum moderately long, slightly surpassing midlength of aedeagal shaft, laterally with serrated margin. Female genitalia. As described for the genus. Immatures. Figs 9 A – F, 10 A – F, 11 A – D, 12 A – D. Nymph 5 th instar. Body length. 1.9 mm (n = 3). Habitus. Slightly dorsoventrally flattened, about twice as long as maximally wide, widest at level of forewing pads and 5 th abdominal segment. Colouration. All parts whitish to very pale yellow. Head. Head without compound eyes, ocelli or traces of them; width at posterior margin of vertex distinctly narrower than pronotum at posterior margin (about 0.4: 1). Vertex short and broad, almost pentagonal, apex anteriorly slightly produced and medially notched, at posterior margin about twice as wide as medially long, lateral and anterior margins ridged, medially a very faint longitudinal carina separating vertex in 2 halves; transition to frons broadly rounded. Frons rather wide, about 1.3 times wider than medially high, maximal width at level of antennae; lateral margins strongly convex, paired intermediate carinae very shallowly convex, well separated from each other, converging towards apex; surface of lateral areas shallowly vaulted, of median area deeply concave; frontoclypeal margin slightly arched and notched. Head with a total of 30 sensory pits, i. e., 12 pits in lateral areas of frons and 3 pits in “ preocular ” area, frontal pits arranged in rows of 6 along intermediate and lateral carinae; variation: in one individual only 5 lateral pits on right side. Sensory pits on head as well as on the other tagmata oval to subcircular, from a cup-like socket at the outer margin arising a seta which is exposed horizontally over the pit without attaining lateral or opposite margins; seta distally knob-like dilated. Post- and anteclypeus shallowly vaulted, smooth, devoid of carinae, post- and anteclypeus separated by a transverse notch. Rostrum distinctly surpassing post-trochanters; tip of rostrum as in adults. Antennae short, scape ring-like; pedicel about 4 times longer than scape, subglobose, distally with about 10 sensory-plaques consisting of a crown of 3–4 longer finger-shaped processes arising from a common socle and 4–5 short rigid spines at base. 3 rd antennal joint (“ flagellum ”) distinct, knob-like, about 0.25 times shorter than pedicel, surface with 2–3 transverse wrinkles, distally continuing in a long arista (“ first projection ” sensu Shi and Yang 1996) and a short peg-like process or arista (“ second projection ” sensu Shi and Yang 1996), both with surface wrinkled; dorsally at distal margin of the 3 rd antennal joint above the bases of the aristae a distinct Bourgoin´s organ consisting of about 20 slender finger-shaped processes forming a distally converging crown. Genae devoid of oblique carina, antennal bases large, subcircular, lamina mandibularis not defined by sutures, distally filiformous. Thorax. Pronotum broad and short, about 5.4 times wider than long in middle line, medially slightly shorter than vertex (0.8–0.9: 1); posterior margin straight transverse; medially a membraneous cleft, no ridged carina; dorsolateral carinae oblique, ridged, reaching from anteromedian corner of disc towards lateral posterior margin, dorsal area of disc along carina with 4 sensory pits; lateral lobes at posterior and ventral margin with a total of 4 sensory pits; surface of disc very shallowly concave, nearly plane, surface of lateral lobes slightly convex. Meso- and metanotum medially divided by a longitudinal membraneous furrow, no median carina. Mesonotum approximately 3.8–4 times wider than medially long, medially about twice as long as pronotum; posterior margin shallowly concave, at lateral discal carina almost rectangularly bent inwards; disc narrow, lateral discal carina diverging laterocaudad, attaining posterior margin; mesonotum with a total of 16 sensory pits; mediad along discal carina 2 sensory pits, laterad of carina close to posterior margin another sensory pit; forewing pads large, slightly surpassing midlength of hindwing pads; pads sublaterally at posterior margin with a short ridge and a long subcostal carina; forewing pads with a single pit laterad of sublateral ridge, 2 pits at distal margin and 2 pits between subcostal and costal margin. Metanotum about 3.5 times wider than medially long, medially about as long as mesonotum, posterior margin oblique with pads rounded, attaining anterior margin of first abdominal tergite; disc plane, narrow, lateral discal carina straight, slightly diverging caudad, laterad along carina 2 sensory pits. Legs moderately long, slender, normally shaped, without significant dilation or flattening of particular limbs. Pro- and meso-femora at outer distal margin with a short tooth-like protuberance; pro- and mesotarsomeres 2 - jointed with 1 st tarsomere rather short, scale-like; post-tarsomeres 3 - jointed. Post-trochanters medially with a narrow row of 10 parallel ribs forming a cog-wheel structure. Post-femora anteriorly at outer side with a small knob-like protuberance. Post-tibiae about twice as long as post-tarsomeres combined, laterally with 2 small spines, one near base, the other distinctly basad of midlength; distally with 5 coarse spines and a short post-tibial spur. Postbasitarsi only little longer than 2 nd and 3 rd post-tarsomeres together, about 3 times longer than post-tibial spur; postbasitarsi distally with 4, 2 nd post-tarsomeres with 3 stout spines in a transverse row, 2 nd post-tarsomeres relatively short. Pretarsi with aroliae very large, pillow-like with several longitudinal ribs, lateral claws short. Post-tibial spur subconical, terete, with a few irregularly ordered bristles. Abdomen. Tergites mediodorsally incised, distal tergites with sharply ridged crest, no wax-plates on tergites; tergites I – III devoid of sensory pits; tergite IV with a single sublateral pit, extralateral area devoid of pit; tergite V with a sublateral and a lateral pit, tergites VI – VIII with a subdorsal, a sublateral and a lateral pit, extralateral areas V – VIII anteriorly with a single pit; an intermediate or sublateral carina of tergites missing, only on tergite VIII a short sublateral ridge; 9 th abdominal segment with a single dorsal and 2 ventrocaudal sensory pits; in the late 5 th instar males the outline of the pygofer and lateral anal combs, and in the females the developing of paired gonapophyses of the ovipositor are visible. In the individuals examined the dicision for a particular sex appears difficult as there are on one hand clearly recognizable paired structures which may be interpreted as gonapophyses, on the other hand mediolateral protuberances which may be interpreted as anal combs. Stigmata are present in the intersegmental fold between extralateral parts of tergites and sternites, mostly located anteriorly. Nymph 4 th instar. Body length. 1.25 mm (n = 2). Habitus, coloration and equipment with sensory pits as in 5 th instar nymphs; rostrum relatively longer, attaining anterior margin of 5 th sternite; pedicel with surface smooth, distally as in 5 th instar with about 10 sensory-plaques; 3 rd antennal joints relatively larger, with 2 distinct transverse wrinkles with serrate margin; Bourgoin´s organ large, consisting of about 20 long finger-shaped processes arising from a common plate. In mesonotum forewing pads shorter, attaining anterior margin of metanotal hindwing pads, posterior margin shallowly concave. Legs in shape, proportions and spine-configuration of hindlegs as in 5 th instar, cog-wheel structure of post-trochanters with about 10 parallel ribs. Anlagen of male and female genitalia as in 5 th instar. Nymph 3 rd instar. Body length. 0.98 mm (n = 1). Habitus, coloration, proportions, number and arrangement of sensory pits as in 5 th and 4 th instar nymphs; rostrum long as in 4 th instar; pedicel 3.4 times longer than scape (in 4 th and 5 th instar about 4 times longer), distally with about 6 sensory-plaques (10 in 4 th and 5 th instar); 3 rd antennal joint relatively large with surface finely sculptured, Bourgoin´s organ distinct, shaped as in 4 th and 5 th instar. Legs with cog-wheel structure of post-trochanters as in 5 th and 4 th instar with 10 parallel ribs; all tarsi 2 segmented, in second post-tarsomeres limitation of later separation marked by 2 small spines on ventral side; lateral margins of post-tibiae without spines, or spines vestigial; post-tibial spur rather small, developed as rigid cone. Anlage for genital structures faint. Etymology. The species epithet is a noun in apposition treated as indeclinable. It is derived from the 1994 movie « Star Trek: Generations », in which Nexus refers to a place of bliss that connects different points in space-time, acting as a link between distinct realities. The gender is masculine. Distribution. The species newly described herein was collected in a cave located in the Serra do Ramalho, a vast karstic province situated in southwestern Bahia, Brazil. This region lies within the São Francisco Carbonate Supergroup, particularly the Bambuí Group, and is renowned for its thick limestone deposits and complex subterranean networks (Auler et al. 2001). The karst extends over roughly 12,000 km ², framed by the Carinhanha and Corrente rivers, which are important tributaries of the São Francisco River, forming one of the largest continuous carbonate outcrops in eastern South America. The lithostratigraphy of Serra do Ramalho is dominated by the Sete Lagoas and Lagoa do Jacaré formations, which are composed mainly of calcilutites, calcarenites, calcirudites, and dolomitic facies (Ferreira et al. 2023). These rock assemblages have given rise to an impressive array of geomorphological features, including extensive cave systems, dolines, sinkholes, and subterranean drainage networks. Further details on the geological framework and hydrogeological dynamics of the region are available in Ferreira et al. (2023). Climatically, the area is classified as tropical savanna (Aw, Köppen system). The local regime is characterized by a pronounced dry season extending from March to October, followed by a shorter wet season. Annual precipitation averages approximately 640 mm, while mean temperatures hover near 26 ° C (Alvares et al. 2013; INMET 2018). This seasonal variability strongly influences the ecological processes of the karst, shaping both the surface vegetation and the subterranean communities. Ecological associations, habitat characteristics, and potential threats concerning the new species are discussed in the section “ Ecological Remarks ” below. Ecological remarks. Spelaeodelphax nexus sp. nov. is currently restricted to a single site within the Água Clara Cave System (ACCS), a large and linear subterranean complex developed in calcarenitic strata of the Sete Lagoas Formation (Fig. 1 C). The system comprises four major caves arranged along a hydrological continuum: Gruna da Água Clara (13,880 m), Gruna dos Índios (510 m), Lapa dos Peixes I (9,320 m; Fig. 1 C, D), and Lapa dos Peixes II (2,100 m). Recognized as the richest tropical subterranean system in terms of obligate cave fauna, the ACCS harbors at least 52 troglobitic and stygobitic species (Ferreira and Souza-Silva 2023; Vaz et al. 2025). The new species was discovered exclusively in Lapa dos Peixes I (Fig. 2 A – C), where airflow between two distant entrances creates a pronounced seasonal microclimatic gradient. While much of the conduit experiences severe desiccation during the austral winter, the sector where the population occurs remains permanently humid owing to a permanent water body. This microhabitat is among the most environmentally stable zones of the entire system and sustains the highest concentration of troglobitic taxa within the ACCS (Ferreira and Souza-Silva 2023). Within this humid conduit, S. nexus was consistently found in association with root mats that penetrate the cave through fissures in the rock, descending from a small upper conduit connected to the main passage where the water body occurs (Fig. 2 C). All individuals were observed either directly on the roots lying along the cave floor or in their immediate vicinity, occasionally sheltered beneath rocks. In contrast, root tufts hanging from the ceiling or walls did not harbor specimens. This apparent preference for floor-level roots may be related to the higher moisture content of substrates in this area, compared with the relatively drier walls and ceiling. Both adults and nymphs were documented in successive surveys (Fig. 2 D – F), suggesting continuous reproduction throughout the year. Although the host plant species remains unidentified, precluding an evaluation of trophic specialization, it is clear that the species depends on these roots as a food resource. The apparent confinement of S. nexus to a single, permanently humid conduit suggests extreme micro-endemism and high vulnerability to environmental fluctuations or disturbance. Although this species likely occurs in inaccessible crevices (mesocaverns), we currently lack precise data on the permeability of the Karst in this locality. In addition, the exact distance between the surface and the conduit where the samples were collected near the roots cannot be precisely determined but was estimated to be at least 50 meters. Surrounding landscapes exert considerable pressure on the ACCS and are threatened. Widespread deforestation (Fig. 13 A) driven by agriculture and charcoal production (Fig. 13 B) has already altered surface processes near cave entrances, reducing organic inputs, increasing erosion, and accelerating sediment deposition within caves. Such changes homogenize substrates and degrade aquatic and terrestrial microhabitats, disproportionately impacting highly specialized subterranean fauna (Pellegrini et al. 2016; Cardoso et al. 2022). Given both the exceptional biodiversity of the ACCS and the restricted distribution of S. nexus, the implementation of urgent conservation measures is imperative. We strongly recommend the creation of a legally protected conservation unit that encompasses not only the subterranean network but also the surrounding karst landscape and its contributing catchments. Protection of this broader system under strict environmental regulations is essential to preserve ecosystem integrity and to ensure the persistence of this newly described species along with the remarkable cave-restricted assemblages of the Água Clara Cave System.

Published as part of Santos, Júlio C. C. V., Asche, Manfred, Hoch, Hannelore & Ferreira, Rodrigo L., 2026, First record of a troglobitic Delphacidae in the Neotropics: Spelaeodelphax nexus Santos & Asche gen. nov. et sp. nov. from Brazil (Hemiptera, Fulgoromorpha), pp. 1-25 in Subterranean Biology 55 on pages 1-25, DOI: 10.3897/subtbiol.55.175661