Genus Rivudiva Lugo-Ortiz & McCafferty, 1998 Key to the species in the nymphal stage (adapted from Salles & Nascimento 2009) 1. Abdominal sterna with simple setae; hind wing pads present ........................ 2 (minantenna group) – Abdominal sterna with robust, apically pointed setae (Fig. 3B); hind wing pads absent ................. 3 2. Setae on dorsum of fore femur long (as long as maximum width of femur) and apically pointed (Salles & Nascimento 2009: fig. 32) ....................... R. minantenna Lugo-Ortiz & McCafferty, 1998 – Setae on dorsum of fore femur short (at most ⅓ maximum width of femur) and apically blunt (Salles & Nascimento 2009: figs 7, 30–31) ................................. R. inma Salles & Nieto in Salles et al., 2020 3. Scape and pedicel without apically pointed setae; fore tarsus with long setae (Salles & Nascimento 2009: fig. 17) .................................................................... R. oonirikoperi Cruz in Salles et al., 2020 – Scape and pedicel with apically pointed setae (Fig. 1A); fore tarsus without long setae ................... ........................................................................................................................... 4 (trichobasis group) 4. Labrum with medial emargination (Figs 1B, 12A), hypopharynx with distomedial projection (Figs 1F, 12F) ................................................................................................................................................... 5 – Labrum without medial emargination (Figs 4A, 8A, 16A), hypopharynx without distomedial projection (Figs 4F, 8I) ....................................................................................................................................... 6 5. Maxillary ventral canine not laterally folded over the canines (Fig. 12D); labial palp segment III wide (Fig. 12G) ................................................................................... R. uiara sp. nov. (Central Amazon) – Maxillary ventral canine laterally folded over the canines (Fig. 1E); labial palp segment III narrow (Fig. 1G) ........................................ R. trichobasis Lugo-Ortiz & McCafferty, 1998 (Pampa Biome) 6. Patella-tibial suture on foreleg absent (Fig. 9A); outer arc of setae on glossae sinuous (Fig. 8K); distal lobe of maxillary palp segment II with half of width of segment II apex (Fig. 8D) .......................... .......................................................................................... R. oxum sp. nov. (Southwestern Amazon) – Patella-tibial suture on foreleg present (17A); outer arc of setae on glossae not sinuous (Fig. 16G); distal lobe of maxillary palp segment II with the same width of segment II apex (Figs 4E, 16D) .... ........................................................................................................................................................... 7 7. Segment III of labial palp apically pointed (Fig. 4G); paraproct with nine to eleven marginal spines (Fig. 6B) ........................................................... R. amazona sp. nov. (Amazon in southern Roraima) – Segment III of labial palp broadly pointed (Fig. 16F); paraproct with two marginal spines (Fig. 18B) ......................... R. naia sp. nov. (ecotone between Amazon forest and Roraima savanna)

Published as part of Cruz, Paulo Vilela, Boldrini, Rafael, De Lima, Cláudia R. T. & Hamada, Neusa, 2022, It is a mess! How many species are in Rivudiva trichobasis Lugo- Ortiz & McCafferty, 1998 (Ephemeroptera: Baetidae)?, pp. 153-191 in European Journal of Taxonomy 789 (1) on page 156, DOI: 10.5852/ejt.2022.789.1639, http://zenodo.org/record/5965407