It is a mess! How many species are in Rivudiva trichobasis Lugo- Ortiz & McCafferty, 1998 (Ephemeroptera: Baetidae)? Author Cruz, Paulo Vilela 34F85F41-2743-4248-813F-0CEEE63FE649 Universidade Federal de Rondônia (UNIR), Programa de Pós-Graduação em Ciências Ambientais, Programa de Pós-Graduação em Conservação e Uso de Recursos Naturais, Laboratório de Biodiversidade e Conservação, CEP 76940 - 000, Rolim de Moura, Rondônia, Brazil. & Instituto Nacional de Pesquisas da Amazônia (INPA), Coordenação de Pós-Graduação (COPOG), Divisão do Curso em Entomologia (DiEnt), Coordenação de Biodiversidade (CoBio), Laboratório de Citotaxonomia e Insetos Aquáticos, CEP 69067 - 375, Manaus, Amazonas, Brazil. pvilelacruz@gmail.com Author Boldrini, Rafael FDC9283D-2B03-4BA9-8631-FB7A57F4D875 Universidade Federal de Roraima (UFRR), Campus Paricarana, Centro de Estudos da Biodiversidade (CBio), CEP 69310 - 000, Boa Vista, Roraima, Brazil. rafaelboldrini.2@gmail.com Author De Lima, Cláudia R. T. 18795D2E-427D-4A26-B112-70C929CA5B95 Instituto Nacional de Pesquisas da Amazônia (INPA), Coordenação de Pós-Graduação (COPOG), Divisão do Curso em Entomologia (DiEnt), Coordenação de Biodiversidade (CoBio), Laboratório de Citotaxonomia e Insetos Aquáticos, CEP 69067 - 375, Manaus, Amazonas, Brazil. claudia.tavares.lab@gmail.com Author Hamada, Neusa 0D02F36C-6B09-423C-95A6-6179E9808CD5 Instituto Nacional de Pesquisas da Amazônia (INPA), Coordenação de Pós-Graduação (COPOG), Divisão do Curso em Entomologia (DiEnt), Coordenação de Biodiversidade (CoBio), Laboratório de Citotaxonomia e Insetos Aquáticos, CEP 69067 - 375, Manaus, Amazonas, Brazil. neusaha@gmail.com text European Journal of Taxonomy 2022 2022-02-03 789 1 153 191 http://zoobank.org/370ed343-0f14-4776-9ef0-086f0fed62c7 journal article 20809 10.5852/ejt.2022.789.1639 f4ad0566-349b-4936-a5dc-b3e36d2b5ead 2118-9773 5965407 370ED343-0F14-4776-9EF0-086F0FED62C7 Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998 Figs 1–3 Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998: 64 ( type material). Rivudiva trichobasis – Cruz et al. 2018: 10 , figs 23, 29. — Lugo-Ortiz & McCafferty 1998: 64 (with some doubt, partim). — Salles et al. 2020: 49 (with some doubt). not Rivudiva trichobasis – Cruz et al. 2011: 60 . — Falcão et al. 2011: 539 . — Boldrini et al. 2012: 93 . — Boldrini & Cruz 2014: 5 . Diagnosis (adapted from Salles et al. 2020 ) NYMPH. The combination of the characters: 1) labrum with medial emargination ( Fig. 1B ); 2) labrum ventral surface with simple robust row of setae on distal margin ( Fig. 1B ); 3) left mandible with incisors fused at middle length ( Fig. 1C ); 4) maxillary palp segment II with robust apical lobe ( Fig. 1E ); 5) ventral canine expanded, laterally folded over canines; 6) hypopharynx with small distomedial projection ( Fig. 1F ); 7) outer arc of setae on glossa with apical half not sinuous, far from distal margin ( Fig. 1G–H ); 8) labial palp segment III narrow and conical ( Fig. 1G ); 9) dorsal margin of forefemur with one row of long spine-like setae from base to apex ( Fig. 2A ); 10) forefemur on anterior surface with medial row of elongate blunt setae ( Fig. 2A ); 11) patella-tibial suture absent; 12) distal margin of terga with wide marginal spines ( Fig. 3A ). Material examined Paratype BRAZIL • 1 nymph ; Rio Grande do Sul State , Arroio dos Vargas ; 30°50′ S , 53°10′ W ; 120 m a.s.l. ; Nov. 1964 ; F. Plaumann leg; IBN slide #270 . Redescription Nymph HEAD. Antenna ( Fig. 1A ). Flagellum with minute spines on apex of each segment. Labrum ( Fig. 1B ). Rectangular, length about 0.7× maximum width; distal margin with medial emargination, one row of robust, eventually pectinated, setae from lateral to middle; one row of thin bifid setae on distal margin not reaching distolateral margin; dorsal surface, near distal margin, with many thin setae over surface. Left mandible ( Fig. 1C ). Incisors partially cleft in two sets (fused at middle length); outer and inner set of incisors respectively with 4 + 3 denticles, outer incisor without spine-like process; prostheca robust and apically pectinate; margin between prostheca and mola straight; tuft of spine-like setae at base of mola absent; subtriangular process wide; denticles of mola not constricted; mola with one large denticle; outer margin convex. Right mandible ( Fig. 1D ). Incisors fused at base; outer and inner set of incisors respectively with 3 + 3 denticles, outer incisor with one spine-like process; prostheca stout, bifurcated at middle, 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 one simple setae; first process of mola triangular, second expanded and straight; outer margin convex. Maxilla ( Fig. 1E ). Maxillary palp 1.6× length of galea-lacinia; segment II 1.0× length of segment I, apex with robust apical lobe; ventral canine expanded, laterally folded over canines; set of distal setae of inner-ventral row clavate, base of maxilla broken. Hypopharynx ( Fig. 1F ). Lingua longer than superlingua, sub-quadrangular with a small distomedial projection covered by tuft of simple setae; superlingua with rounded outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Labium ( Fig. 1G–H ). Glossa slightly broad at base, with parallel margins, distal margin slightly rounded with small concavity and shorter than paraglossa; inner margin with two short spine-like setae on half; ventral surface covered by thin setae; dorsal surface with inner arc close to inner margin, outer arc basal half of row close to outer margin, apical half of row not sinuous, far from distal margin; one long robust blunt seta on apex. Paraglossa curved inward; apex with two rows of robust and long spine-like setae; outer margin with two long setae; dorsal surface with three longitudinal rows of setae, first row near inner margin longer than half of length, with long robust setae; second with half of length of the inner row, with long robust setae; and third near to outer-distal margin, with long setae, ventral surface with one row of four setae near to ventral margin. Labial palp with segment I 0.8× length of segments II and III combined; inner distal protuberance of segment II rounded, covered with thin, long simple setae; segment III narrow and conical (folded in slide studied), covered by thin simple setae, dorsal surface with robust spine-like setae near inner margin. Fig. 1. Rivudiva trichobasis Lugo-Ortiz & McCafferty, 1998 , paratype (IBN slide #270). A . Scape and pedicel. B . Labrum (left v.v., right d.v.). C . Left mandible. D . Right mandible. E . Apex of maxilla (base was deformed in slide). F . Hypopharynx. G . Labium (left v.v., right d.v.). H . Shape of distal rows of setae of glossa. Not to scale. THORAX. Foreleg ( Fig. 2A–C ). Femur length about 3.2× maximum width; anterior surface with one medial row of elongate and blunt setae, one row of long spine-like setae near ventral margin not reaching apex; posterior surface with one row of long spine-like setae near dorsal margin not reaching apex, and one row of long spine-like setae near ventral margin reaching apex. Tibia. Dorsally bare; ventral margin with one row of long spine-like setae increasing in length to apex; patella-tibial suture absent. Tarsus. Ventral margin with one row of spine-like setae. Tarsal claws ( Fig. 2B ) 0.3× length of tarsus, with two rows of conical denticles not reaching apex. Hind leg ( Fig. 2D–E ). Femur anterior surface with one row of spine-like setae near dorsal margin on distal half, one row of long spine-like setae near ventral margin; posterior surface with one row of long spine-like setae near dorsal margin not reaching apex, one row of spine-like setae near ventral margin reaching apex. Tibia. Dorsally bare; ventral margin with one row of small blunt setae; patella-tibial suture present. Tarsus. Ventral margin with one row of small blunt setae. Tarsal claws ( Fig. 2D ) 0.5× length of tarsus, with two rows of small conical denticles reaching apex. ABDOMEN. Terga III and VI with large medium brown mark. Posterior margin of terga with small triangular spines ( Fig. 3A–B ). Gills missing. Paraproct ( Fig. 3C ) with nine to twelve wide marginal spines, posterolateral extension with spines. Cerci ( Fig. 3D ) with lateral spines on every segment. Paracercus ( Fig. 3E ) without spines. Comments Based on the study of type material, records from Brazil , Roraima ( Falcão et al. 2011 ), Rondônia ( Boldrini & Cruz 2012 ), Amazonas ( Cruz et al. 2011 ) and Maranhão ( R. sp. X) ( Boldrini et al. 2012 ), are not R. trichobasis . The specimens from Espírito Santo ( Brazil ) ( Salles et al. 2020 ) and Paraguay ( Paraguarí ) could not be evaluated. Distribution Brazil ( Rio Grande do Sul ). Paraguay ( Paraguarí ) is treated here as putative; records from Espírito Santo ( Brazil ) ( Salles et al. 2020 ) are treated here as putative and must be evaluated.