New species of Rivudiva Lugo-Ortiz & McCafferty (Ephemeroptera: Baetidae) with comments on R. minantenna Lugo-Ortiz & McCafferty and R. trichobasis Lugo-Ortiz & McCafferty Author Salles, F. F. Museu de Entomologia, Depto. de Entomologia, Universidade Federal de Viçosa, CEP 36.570 - 900, Viçosa, MG, Brazil. frederico. salles @ ufv. br; https: // orcid. org / 0000 - 0001 - 8331 - 5929 Author Nieto, C. Instituto de Biodiversidad Neotropical (IBN), CONICET-U. N. T. & Facultad de Ciencias Naturales, Universidad Nacional de Tucumán, San Miguel de Tucumán, 4.000 Tucumán, Argentina. Author Cruz, P. V. Universidade Federal de Rondônia - UNIR, Programa de Pós-Graduação em Ciências Ambientais, Laboratório de Biodiversidade e Conservação - LABICON, CEP: 76940 - 000, Rolim de Moura, Rondônia, Brazil. text Zootaxa 2020 2020-05-29 4786 1 37 52 journal article 21269 10.11646/zootaxa.4786.1.3 70d743db-654b-4050-a05f-a5c71b54e14e 1175-5326 3990784 625F197D-9D26-4B00-AF3E-3045586ECB07 Rivudiva oonirikoperi Cruz , sp. nov. Material examined . Holotype (male nymph on slide): BRAZIL , Amazonas state, São Gabriel da Cachoeira , stream on BR 307 Km 13, 00 o 04’44.6”S/067 o 00’15.9”W, 26.viii.2011 , P. V . Cruz , A.S. Fernandes and E. Reis cols. ( INPA ) . Paratype : one nymph, same data as holotype ( INPA ). Diagnosis Nymph . 1) antenna without spine-like setae on scape and pedicel; 2) distal margin of labrum without medial emargination ( Fig. 11 ); 3) outer margin of mandibular incisors with spine-like process ( Figs 12–13 ); 4) tuft on apex of lingua formed by short simple setae ( Fig. 14 ); 5) maxillary palp long, 2.1× the length of galea-lacinia ( Fig. 15 ); 6) glossa subelliptical, not expanded at base ( Fig. 16 ); 7) medial protuberance of labial palp segment II strongly projected medially ( Fig. 16 ); 8) hind wing pads absent; 9) inner margin and anterior surface of fore tarsus with robust long spinelike setae ( Fig. 17 ); 10) paraproct with three marginal spines, posterolateral extension without spines ( Fig. 20 ). Imago . Unknown. Description Nymph. Lengths: body, 3.2 mm ; cercus, 1.6 mm . Head. Coloration: Pale yellow. Antenna white. Compound eyes light orange. Antenna. Scape and pedicel without spine-like setae; flagellum with minute spines and thin setae on apex of each segment. Labrum ( Fig. 11 ). Rectangular, length about 0.5x maximum width; distal margin without medial emargination, anterolateral and distal margin with robust bifid setae; dorsal surface near distal margin with two rows of thin simple setae; ventral surface with anterolateral robust bifid setae. Left mandible ( Fig. 12 ). Incisors cleft in two sets; outer and inner set of incisors respectively with 3 + 3 denticles, outer incisor with spine-like process; prostheca robust and bifid at base, internal lobe slender, external lobe robust; margin between prostheca and mola straight; tuft of spine-like setae at base of mola absent; subtriangular process wide; denticles of mola not constricted; lateral margins convex. Right mandible ( Fig. 13 ). Incisors cleft in two sets; outer and inner set of incisors respectively with 2 + 2 denticles and an outer spine-like process; prostheca stout, bifurcated at apex, inner lobe longer and pectinate; margin between prostheca and mola straight; tuft of spine-like setae at base of mola present; denticles of mola not constricted; apex of mola with two simple setae; lateral margins convex. Hypopharynx ( Fig. 14 ). Lingua longer than superlingua, sub-quadrangular with a distomedial pointed projection covered by tuft of simple setae; superlingua with rounded outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Maxilla ( Fig. 15 ). Maxillary palp long, 2.1× length of galea-lacinia; segment II 0.8× the length of segment I, apex with inner lobe; maxillary palp with thin simple setae scattered over surface; canines slender, dentisetae similar to canines. Labium ( Fig. 16 ). Glossa sub-elliptical, basally broad, narrowing apically and shorter than paraglossa; inner margin with row of spine-like setae on apical half; ventral surface covered by thin setae. Paraglossa curved inward; apex with two rows of robust and long spine-like setae; outer margin bare; dorsal surface with many long spine-like setae. Labial palp with segment I 0.9× the length of segments II and III combined; medial protuberance of segment II strongly projected medially, outer margin and distomedial protuberance covered by thin, long simple setae; segment III conical, length 1.1× width, covered by thin simple setae on outer margin, ventral surface with robust spine-like setae near outer margin. Thorax. Mesothorax with two large brown marks ( Fig. 21 ). Hind wing pads absent. Foreleg ( Fig. 17 ). Femur, tibia and tarsus light yellow. Ratio of foreleg 1.1:(1):0.6:0.17. Forefemur. Length about 2.6× maximum width; dorsal margin, anterior and posterior surface covered by robust long spine-like setae. Tibia. Dorsally bare; inner margin and anterior surface with few robust long spine-like setae. Tarsus. Ventral margin and anterior surface with robust long spine-like setae. Tarsal claws ( Fig. 18 ) 0.3× the length of tarsus, with two rows of conical denticles. Mid and hind leg ( Fig. 19 ). Anterior surface of tibiae and tarsi without robust long setae; ventral margin of tibiae and tarsi with one row of short blunt setae. Abdomen. Terga pale yellow, I and II with two large brown marks ( Fig. 21 ); surface covered by pores and short spine-like setae as in fig. 37; posterior margin smooth. Sterna white. Gills missing. Paraproct ( Fig. 20 ) with three marginal spines, posterolateral extension without spines. Cerci with lateral spines on every segment. Terminal filament without spines. Etymology . Õonirikoperi is a word in Baniwa language, from Baniwa indigenous ethnicity, a group of Native American inhabiting the area where the species was collected. This word is attributed to any specimen of Ephemeroptera . However, its literal meaning is “a being [malevolent] that walk inside the water”. The name is in apposition. Comments . Rivudiva venezuelensis ( Traver, 1943 ) was described based solely on male and female imagos from Venezuela and since then no other material has been assigned to it. Given the absence of hind wings in this species and in R. oonirikoperi , sp. nov. , there is a possibility that this new species is in fact the nymphal stage, and thus represents a junior synonym of R. venezuelensis . Obtaining additional material from both species, including nymphs and reared adults, would be the best solution to solve this doubt. Distribution . Brazil , Amazonas, São Gabriel da Cachoeira ( Fig. 41 ). Biology . Nymphs were collected on sand in a small ( 90 cm width) and well preserved stream with low water flow.