Spelaeometra ybykoara Serafim & Ferreira 2026, sp. nov.
Authors: Serafim, Ingrid R., Santos, Júlio C. C. V., Ferreira, Rodrigo L.
Type: Taxonomic treatment
Published: 2026-07-20
Keywords: Biodiversity, Taxonomy, Animalia, Arthropoda, Insecta, Hemiptera, Hydrometridae, Spelaeometra, Spelaeometra ybykoara

<p><b><i>Spelaeometra ybykoara</i> Serafim & Ferreira sp. nov.</b></p><p>urn:lsid:zoobank.org:act: 42112360-0489-4016-AE9B-D77716E84C70</p><p>Figs 1D, 2–7, 15C</p><p><b>Diagnosis</b></p><p><i>Spelaeometra ybykoara</i> sp. nov. can be distinguished from all other species of the genus by the following combination of characters: antennae not exceeding body length, compound eyes with 16 ommatidia; and parameres tripartite, with well-developed subtriangular apical process ventrad, almost reaching the middle of the distal arm.</p><p><b>Etymology</b></p><p>The specific epithet is a noun in apposition derived from the Tupi word <i>yby-koara</i>, meaning “cave inhabitant.” This term originates from the Tupi language, spoken by indigenous peoples of Brazil, and is used here to honor the region’s cultural heritage and its deep connection to the land. As a noun in apposition, the epithet is indeclinable and does not change to agree in gender with the genus name.</p><p><b>Type material</b></p><p><b>Holotype</b></p><p>BRAZIL • <b>♂</b>; Bahia state, Carinhanha municipality, Lapa dos Peixes I cave; 13°50′16.750″ S, 43°58′29.060″ W; 4 Jun. 2024; Ferreira R.L. leg.; preserved; ISLA 126339.</p><p><b>Paratypes</b></p><p>BRAZIL • 1 <b>♂</b>; same collection data as for holotype; dissected; ISLA 126340 • 2 <b>♀♀</b>; same collection data as for holotype; ISLA 126342–43 • 2 juvs; same collection data as for holotype; ISLA 126345 • 1 ♂, 2 <b>♀♀</b>; same collection data as for holotype; 17 Jul. 2024; ISLA 126346–48 • 2 <b>♀♀</b>; same collection data as for holotype; 7 May 2023; ISLA 126349–50.</p><p><b>Description</b></p><p><b>Male apterous</b></p><p>BODY LENGTH. 2.48–2.60 mm (n = 3; including one small, one medium, and one large specimen), maximum width (at abdomen) 1.19–1.26 mm (n = 3).</p><p><b>Structural characters holotype</b></p><p>HEAD. Length 0.77, width 0.26; length interocular 0.25, transocular 0.33, ocular width 0.06, ocular length 0.09; eyes with 16 ommatidia present. Antennal segments I–IV= 0.27, 0.24, 0.93, 1.09. Rostrum length 1.67, lip segment length I–IV = 0.10, 0.06, 1.11, 0.40, respectively.</p><p>THORAX. Length 0.43, width 0.47, with only the pronotum visible, covering the mesonotum and metanotum.</p><p>LEGS. Segment lengths: anterior femur, tibia, tarsus I, tarsus II, tarsus III = 0.74, 0.88, 0.04, 0.16, 0.11; middle femur, tibia, tarsus I, tarsus II, tarsus III = 0.83, 1.04, 0.03, 0.19, 0.10; posterior femur, tibia, tarsus I, tarsus II, tarsus III = 1.12, 1.67, 0.03, 0.3, 0.12.</p><p>ABDOMEN. Length 1.23, maximum width 0.68, minimum width 0.48. Length of abdominal tergites I–VII = 0.14, 0.17, 0.15, 0.19, 0.18, 0.19, 0.19; maximum width of abdominal tergites I–VII = 0.41, 0.37, 0.32, 0.31, 0.29, 0.27, 0.22. (Table 1).</p><p><b>General description</b> (paratype, ♂, ISLA 126340)</p><p>COLORATION (preserved specimen) (Figs 2A–C, 3A–C). head and thorax, brilliant orange-yellow (67, sRGB Centroids for ISCC-NBS Level 3 Categories), basally on the thorax and apically on the abdomen, strong orange-brownish (68). Appendage insertions light yellow (86), bringing dark to moderate yellow (87) along their length. Abdomen and male genitalia strong yellowish-brown (74).</p><p>HEAD. In dorsal view (Fig. 3A), lateral margin slightly concave, carinae behind the eyes totally elevated. In lateral view (Fig. 3C), dorsal margin convex, ventral margin sinuous with two small convexities and two small concavities. In ventral view (Fig. 3B), longitudinal carinae weakly elevated. Rostrum (Fig. 2B), long and slender, surpassing the third abdominal segment. Cephalic trichobothria (Figs 3A, C, 4F) present, as described for the genus. Compound eyes (Fig. 4C–D) reduced, bearing 16 ommatidia with ocular setae present; ocelli absent. Antennae (Fig. 2A–C), not exceeding body length; antennal segments as described for the genus.</p><p>THORAX. In dorsal view (Fig. 3A) with pronotum slightly bilobed laterally, almost linear distally. Wings (Fig. 3A) completely absent, with interior wing buds visible. In lateral view (Fig. 3C), thoracic pleurae as described for the genus. In ventral view (Fig. 3B), sternum bearing paired, sinuous, slightly raised longitudinal carinae.</p><p>ABDOMEN. In dorsal view, mediotergites almost equal in length (Fig. 4A, G). Scent orifice on mediotergite IV obscure (Fig. 4, g 1). In ventral view, some regions brownish.</p><p>LEGS (Fig. 2A–C). Anterior and posterior legs with few distinct setae. Femur slender proximally. Tibiae long and robust (Fig. 2A–C). Tarsi as in other species of the genus, except for tarsus II: long on the anterior and middle legs, short on the hind leg. Middle leg with one claw on tarsus III (Fig. 5A), fore and hind legs with two claws on the apex of tarsus III (Fig. 5B).</p><p>MALE GENITALIA (Fig. 6A–F). Parameres, bilaterally symmetrical, relatively large and broad, tripartite, with a short basal stem, distal arm with concave dorsal margin, convex ventral margin, with well-developed subtriangular apical process ventrad, almost reaching the middle of the distal arm.</p><p><b>Female apterous</b></p><p>BODY LENGTH. 2.53–2.68 (n = 3; including one small, one medium, and one large specimen), maximum width (at abdomen) 1.30–1.32 (n = 3). Structural characters as in males, elongated.</p><p><b>Habitat and threats</b></p><p><i>Spelaeometra ybykoara</i> sp. nov. is currently known only from a single locality within the Água Clara Cave System (ACCS), a complex linear network of four major subterranean conduits formed in calcarenitic strata of the Sete Lagoas Formation, which forms striking carbonate outcrops in the region. From upstream to downstream, these caves include Gruna da Água Clara (13 880 m), Gruna dos Índios (510 m), Lapa dos Peixes I (9320 m; Figs 6A–C. 13A, E), and Lapa dos Peixes II (2100 m). The species was recorded exclusively in Lapa dos Peixes I, a cave characterized by a pronounced seasonal microclimatic gradient created by airflow between entrances located at opposite ends of the conduit. While much of the main gallery becomes markedly dry during the austral winter, the section where specimens were collected retains consistently high humidity throughout the year due to the presence of a perennial water body.</p><p>This microhabitat, notable for its environmental stability, hosts the highest richness of troglobitic species in the ACCS (Souza-Silva & Ferreira 2016; Ferreira & Souza-Silva 2023). Despite extensive biological inventories across all caves of the system, <i>Spelaeometra ybykoara</i> sp. nov. (Fig. 7D–E) has not been found outside this discrete habitat, strongly suggesting a highly restricted distribution and microendemism. The species’ apparent confinement to a single, permanently humid conduit section underscores its potential vulnerability to environmental fluctuations and anthropogenic disturbance.</p><p>The broader ACCS is subject to severe external pressures, particularly from agricultural expansion and wood harvesting for charcoal production in the surrounding region (Fig. 7B; Ferreira <i>et al.</i> 2023; Ferreira & Souza-Silva 2023). Extensive deforestation near cave entrances (Fig. 8A–B) has reduced organic input, simplified habitat structure, and increased soil erosion. These changes accelerate the transport of fine sediments into the cave system, leading to substrate homogenization and the degradation of aquatic and terrestrial microhabitats, processes that disproportionately threaten highly specialized hypogean fauna (Pellegrini <i>et al.</i> 2016; Cardoso <i>et al.</i> 2022).</p><p>Given the exceptional biodiversity of the ACCS, including numerous troglobitic taxa, and the apparent micro-endemism of <i>S. ybykoara</i> sp. nov., conservation measures are urgently required. We recommend the establishment of a legally protected conservation unit that encompasses not only the subterranean system but also its contributing catchment microbasins and the surrounding karst landscape. Such a designation, supported by strict environmental regulations, would be essential to safeguard the ecological integrity of this unique subterranean ecosystem and ensure the long-term survival of its highly specialized fauna.</p>