It is a mess ! How many species are in Rivudiva trichobasis Lugo-Ortiz & McCa ff erty , 1998 ( Ephemeroptera : Baetidae ) ?

The original description of Rivudiva trichobasis Lugo-Ortiz & McCaff erty, 1998 is short, with few illustrations. The lack of information resulted in a broad specifi c diagnosis, with emphasis on the spine-like setae on the antenna. Our hypothesis is that the lack of information resulted in many species being hidden behind R. trichobasis name. We evaluated the speci es R. coveloae (Traver, 1971) and R. venezuelensis (Traver, 1943) considering the new evidence. After analyzing the paratype of R. trichobasis and records of the species in Brazil, the hidden-species hypothesis was corroborated. Five new species were identifi ed among the published records of R. trichobasis of which four are described here: R. amazona sp. nov. (Roraima State), R. oxum sp. nov. (Rondônia State), R. uiara sp. nov. (Amazonas State), R. naia sp. nov. (Roraima State). The fi fth species, Rivudiva sp. X from Maranhão State, could not be described due to the poor conservation of the specimen and is therefore left in open nomenclature. Records from Espírito Santo State (Brazil) and from Paraguay are treated as putative and must be evaluated considering the new evidence. Rivudiva venezuelensis and Rivudiva coveloae are diagnosed and illustrated based on type material. After analyzing these two species, we hypothesize that only R. coveloae likely belongs to the genus Rivudiva. However, information on the nymphal stage is needed to corroborate this hypothesis.


Introduction
The genus Rivudiva Lugo-Ortiz & McCaff erty, 1998, although recently established (compared to other genera in the family), already has a rich history. The genus was erected in 1998 to include two species, R. minantenna Lugo-Ortiz & McCaff erty, 1998 (Brazil) and R. trichobasis Lugo-Ortiz & McCaff erty, 1998 (Brazil and Paraguay). Two years later, Orth et al. (2000) reported the genus from French Guyana without specifi c identifi cation and Salles et al. (2004) reported R. minantenna from Rio de Janeiro State, Brazil, considerably extending its known distributional range. Domínguez et al. (2006) examined the type material, adding some important characteristics to the original description of both described species. The genus was treated as rare until Salles & Nascimento (2009), during a mayfl y survey in the Southeastern Region of Brazil, found a good series of nymphs of R. minantenna and reared a few of them in the fi eld. This study brought to light that species of the genus are psammophilous, allowing subsequent fi eldwork sampling to be directed so that a series of discoveries could be made. In the same paper, the authors described the male imago of the genus for the fi rst time (R. minantenna) and, mainly based on a pointed projection on the posterior margin of the subgenital plate, transferred two species only known by their adults to the genus Rivudiva: R. coveloae (Traver, 1971) and R. venezuelensis (Traver, 1943). Cruz et al. (2011) described the male imago of R. trichobasis from Amazonas State (Brazil), emending the generic diagnosis and showing that the singular projection on the subgenital plate was absent. Meanwhile, Falcão et al. (2011) reported R. trichobasis in Roraima State as well as an atypical species that should be placed in a new genus but that was not described at that time. Soon afterwards, Boldrini et al. (2012) recorded R. trichobasis in northeastern Brazil, and Boldrini & Cruz (2014) recorded R. trichobasis in Rondônia State (Brazil). Lima et al. (2013) described the same singular projection on the subgenital plate of the adult male of Paracloeodes charrua Emmerich & Nieto, 2009, stating that it is diffi cult to ascertain whether this projection represents a convergence or an indication that some species of Rivudiva would be better placed in Paracloeodes Day, 1955. The same doubt was suggested by Gutiérrez et al. (2013) in the case of Varipes singuil Nieto, 2004. Considering the discussion of supra-specifi c relationships between genera, Cruz et al. (2018) tested their monophyly using a cladistic approach. As results, Rivudiva, Paracloeodes and Varipes Lugo-Ortiz & McCaff erty, 1998 were delimited, one new genus was erected (Rhopyscelis Cruz, Salles & Hamada, 2018), and one new genus was fl agged, later described as Macuxi Cruz, Salles, Hamada & Falcão, 2020, with no resolution on species known only by their adults .
Two decades of advances in studies of the systematics and taxonomy of the genus has opened the way for further research. The new evidence has allowed understanding why making correct specifi c assignments was a diffi cult task. In order to elucidate the identities of old and new specimens, Salles et al. (2020) reevaluated the types and the specimens studied in Salles & Nascimento (2009), concluding that some of the nymphs of R. minantenna collected in Espírito Santo were actually a new species (R. inma Salles & Nieto in Salles et al., 2020).
The last historical species in the genus to be investigated is R. trichobasis, which is the most recorded and has a wide and disjunct distribution. This species is easily distinguishable from others in the genus by the presence of spine-like setae on the scape and pedicel. However, excluding the spine-like setae on the antenna, the recently collected specimens could be either R. trichobasis or a new species (PVC pers. obs.).
Two synergistic factors hamper the identifi cation of specimens with spine-like setae on the scape and pedicel. First is the lack of suffi cient characteristics and illustrations in the original description; these characteristics are now known to be relevant (as in Apobaetis Day, 1995, see Cruz 2020). The second factor is the paucity of specimens, which makes it diffi cult to understand the morphological variation and challenges species delimitation, resulting in a broad diagnosis of the species focused on one or a few common characteristics (e.g., spine-like setae of antenna).
Furthermore, based on Rivudiva's biology, suspicions about the identity of records were reinforced (PVC pers. obs.). The psammophilous mayfl ies are considered to have low population densities and dispersion abilities, making each population unique (McCaff erty 1991;Lillie 1995;Glazaczow 1997;Jacobus 2013). Thus, the probability is low that R. trichobasis has such a wide distribution, ranging across four Brazilian biomes and in Paraguay.
In order to circumscribe R. trichobasis, R. coveloae and R. venezuelensis, their type material was reevaluated, as well as four of the six records of R. trichobasis in Brazil. Our hypothesis is that the lack of information results in a broad diagnosis for species, with many species hidden behind an easily recognizable one.
The descriptions and measurements were based on the standardized protocol proposed by Hubbard (1995). The photographs of R. trichobasis were taken using a cellphone adapted for use with a microscope.
Digital photographs of R. amazona sp. nov., R. oxum sp. nov., R. naia sp. nov. and R. uiara sp. nov. were taken using a Leica (M165C) stereo microscope with a DFC420 digital camera, and Leica Application Suite ver. 3.8.0 software, photographs of slides were taken using a cellphone; digital photographs of R. venezuelensis and R. coveloae were taken using a cellphone. Final illustrations were prepared according to Coleman (2006).
Nymphs were mounted on slides with Euparal® as the mounting medium. Specimens were preserved in ethanol 80%.

H
. 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 bifi d 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; fi rst 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 . 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, fi rst 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.

T
. Foreleg . 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 . 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.

A
. Terga III and VI with large medium brown mark. Posterior margin of terga with small triangular spines (

Distribution
Brazil (Rio Grande do Sul). Paraguay (Paraguarí) is treated here as putative; records from Espírito Santo (Brazil) ) are treated here as putative and must be evaluated.

Etymology
The name ʻAmazonasʼ was given to native South American women after they attacked a conquest expedition. This species is named in honor of these brave native women. Name in apposition. H . Antenna. Scape and pedicel with spine-like setae; fl agellum with minute spines on apex of each segment. Labrum (Fig. 4A). Rectangular, length about 0.6 × maximum width; distal margin straight, one row of robust, distally bifi d, eventually pectinated, setae from lateral to middle of distal margin; one row of thin bifi d setae on distal margin not reaching distolateral margin; dorsal surface, near distal margin, with one row of thin setae, and many thin setae over surface (not illustrated). Left mandible (Fig. 4B). Incisors partially cleft in two sets (fused at basal third); outer and inner sets of incisors respectively with 4 + 3 denticles, outer incisor with spine-like process; prostheca robust and pectinated; margin between prostheca and mola straight; tuft of spine-like setae at base of mola present; subtriangular process wide; denticles of mola constricted; mola with one large denticle; outer margin convex. Right mandible (Fig. 4C). Incisors fused at base; outer and inner sets of incisors respectively with 3 + 3 denticles, outer incisor with spinelike process; prostheca stout, bifurcated at apex, inner lobe longer; margin between prostheca and mola almost straight; tuft of spine-like setae at base of mola present; denticles of mola not constricted; apex of mola with one simple setae; fi rst process of mola rounded, second expanded and straight; outer margin convex. Maxilla (Fig. 4D-E). Maxillary palp 1.7 × length of galea-lacinia; segment II 1.1 × length of segment I; segment II inner margin straight, outer margin on apex straight, reduced apical lobe; ventral canine enlarged, not laterally expanded; set of distal setae of inner-ventral row rounded. Hypopharynx (Fig. 4F). Lingua longer than superlingua, sub-quadrangular without 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. 4G-H). Glossa oval, slightly broad at base, distally rounded, shorter than paraglossa; inner margin without row of setae; ventral surface covered by thin setae; dorsal surface with inner arc close to inner margin, and outer arc not sinuous and close to outer margin; one small robust blunt seta on apex. Paraglossa curved inward; apex with one row of robust and long spine-like setae; outer margin without setae; dorsal surface with two longitudinal rows of setae, one near to inner margin, one near to outer margin, distally with long robust setae; ventral surface with one row of fi ve 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, with almost straight distal margin, covered with thin setae; segment III robust, conical, and apically pointed; outer margin with short thin setae, dorsal surface with one row of short spine-like setae near inner margin, ventral surface with one row of setae.

Material examined
T . Foreleg (Fig. 5A-C). Femur length about 2.6 × maximum width; dorsal row of setae from distal half to apex; anterior surface with one medial row of long blunt setae, one row of short blunt setae near dorsal margin; posterior surface with one row of long spine-like setae near ventral margin from base to apex, and one medial row of long spine-like setae. Tibia. Dorsally bare; ventral margin with one row of long spine-like setae, patella-tibial suture present. Tarsus. Ventral margin with one row of spine-like setae. Tarsal claws 0.4 × length of tarsus, with two rows of conical denticles not reaching apex. Hind leg . Femur anterior surface with one row of spine-like setae near dorsal margin reaching apex, one row of long spine-like setae near ventral margin reaching apex, one row of spine-like setae near middle; posterior surface with one row of spine-like setae near ventral margin from base to apical third. 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 0.4 × length of tarsus, with two rows of small conical denticles not reaching apex.

A
. Terga (Fig. 7) with all segments white (color lost in alcohol), terga I-IX with two small medial dots, sometimes dots absent; tergum I with one large dot on disto-lateral margin (rare); eventually tergum II, III and IX darker or with large brown pigmentation; terga III and VI with one large medial mark near distal margin; terga VI and VII with disto-lateral transversal brown mark (rare). Posterior margin of terga with elongated triangular spines (Fig. 6A). Gills oblong, longer than next segment, with one medial trachea pigmented. Paraproct (Fig. 6B) with nine to eleven marginal spines, posterolateral extension with spines (broken in holotype and illustrated). Cerci (Fig. 6C) with lateral spines on every segment. Paracercus (Fig. 6D) without spines.

Comments
The diff erences in deepness of the curvature of the distal lobe on the maxillary palp segment II is related to the slide artifact (Fig. 4E).

Etymology
ʻOxumʼ is a female ʻorixáʼ (deity or goddess) from the Ijexá nation, adopted and worshipped in Afro-Brazilian religions. She is the fresh waters ʻorixáʼ (lakes, rivers and waterfalls), of wealth, love, prosperity and beauty. Name in apposition. H . Antenna. Flagellum with minute spines on apex of each segment. Labrum (Fig. 8A). Rectangular, length about 0.6 × maximum width; distal margin straight; one row of robust, distally bifi d, eventually pectinated, setae from lateral to middle of distal margin; one row of thin bifi d setae on distal margin not reaching distolateral margin; dorsal surface with many thin setae over surface. Left mandible (Fig. 8B). Incisors partially cleft in two sets (fused at middle); outer and inner sets of incisors respectively with 4 + 3 denticles, outer incisor with spine-like process; prostheca robust and pectinated; margin between prostheca and mola straight; tuft of spine-like setae at base of mola present; subtriangular process wide; denticles of mola constricted; mola with two large denticles, apex of mola with one simple seta; outer margin convex. Right mandible (Fig. 8C). Incisors fused at base; outer and inner sets of incisors respectively with 3 + 3 denticles, outer incisor with spine-like process; prostheca stout, bifurcated at apex, inner lobe longer; margin between prostheca and mola almost straight; tuft of spine-like setae at base of mola present; denticles of mola not constricted; apex of mola with one simple seta; fi rst process of mola rounded, second expanded and straight; outer margin convex. Maxilla (Fig. 8D-H). Maxillary palpi 1.7 × length of galea-lacinia; segment II 0.9 × length of segment I; segment II with inner distal protuberance, outer margin straight, with long distal lobe half of width of segment II apex; ventral canine enlarged, not laterally expanded; set of distal setae of the inner-ventral row rounded. Hypopharynx (Fig. 8I). Lingua longer than superlingua, sub-quadrangular, without distomedial projection, with medio-distal tuft of simple setae; superlingua with rounded outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Labium (Fig. 8J-K). Glossa slightly expanded at base, with parallel margins, distal margin slightly rounded, shorter than paraglossa; inner margin without row of setae; ventral surface covered by thin setae; dorsal surface with inner arc of robust pointed setae following the inner margin at base, curved at apex, outer arc of long robust setae following the inner margin at base, sinuous at apex; one small robust blunt seta on apex. Paraglossa curved inward; apex with one row of robust and long spine-like setae; outer margin without setae; dorsal surface with four longitudinal rows of setae, inner row longer than half of length of paraglossa, distally with long robust setae; ventral surface with one row of six setae near to inner margin, apex with one row of robust setae. Labial palp with segment I 0.8 × length of segments II and III combined; inner distal protuberance of segment II rounded, covered with thin setae; segment III robust, conical, and apically pointed; outer margin with short thin setae, dorsal surface covered with short spine-like setae, ventral surface with two short spine-like setae, and covered by long thin setae.

T
. Foreleg (Fig. 9A-C). Femur length about 3.3 × maximum width; dorsal margin with one row of long spine-like setae from base to apex; anterior surface with one medial row of blunt setae, one row of long spine-like setae near ventral margin reaching apex, one row of long spine-like setae near dorsal margin; posterior surface with one row of long spine-like setae near ventral margin from base to apex, and one medial row of long spine-like setae from base to apical third. Tibia. Dorsally bare; ventral margin with one row of long spine-like setae at apical half, patella-tibial suture absent. Tarsus. Ventral margin with one row of spine-like setae. Tarsal claws 0.5 × length of tarsus, with two rows of small conical denticles not reaching apex. Hind leg (Fig. 9D-E). Femur dorsal margin with one row of long spine-like setae; anterior surface with one row of spine-like setae near dorsal margin, one row of long spine-like setae near ventral margin, one row of spine-like setae near middle; posterior surface with one row of spine-like setae near ventral margin. Tibia. Dorsally bare; ventral margin with two small blunt setae base, patella-tibial suture present. Tarsus. Ventral margin with one row of small blunt setae. Tarsal claws 0.6 × length of tarsus, with two rows of small conical denticles reaching apex.

A
. Terga (Fig. 11) with all segments yellowish or white (color lost in alcohol), terga I-VIII with two small medial dots, sometimes dots absent; terga III and VIII with one large dot on distal margin (eventually absent); tergum IX darker. Posterior margin of terga with triangular spines (Fig. 10A). Gills oblong, longer than next segment, with one medial trachea pigmented. Paraproct (Fig. 10B) with seven to nine marginal spines, posterolateral extension with spines. Cerci (Fig. 10C) with lateral spines on every segment. Paracercus (Fig. 10D) without spines.

Comments
The variation presented in Fig. 8E-F is related to the slide mount artifact. In Fig. 8E, the maxillary palp is in outer margin view, while in Fig. 8G-H it is in lateral view. The palps presented in Fig. 8G-H are true variations of the segment II and its distal lobe.    Diagnosis I (adapted from Cruz et al. 2011). 1) dorsal portion of turbinate eyes with inner margins not parallel, divergent distally (Cruz et al. 2011: fi gs 1-2); 2) length of forewing about 3.7 × width (Cruz et al. 2011: fi g. 3); 3) hind wings absent; 4) terga III and VI of abdomen with one large medial red mark near distal margin (Cruz et al. 2011: fi gs 4-5); 5) unistyliger cylindrical (Cruz et al. 2011: fi g. 6); 6) fi rst segment of gonostylus short, length less than half of second segment, third segment clavate (Cruz et al. 2011: fi g. 6); 7) styliger plate concave, without spine (Cruz et al. 2011: fi g. 6); 8) gonovectis short, sinuous, not deep into segment IX.

Etymology
ʻUiaraʼ is the Rivers Queen in Amazonian folklore a divinity that protects waters and kills men. Name in apposition. H . Antenna. Flagellum with minute spines on apex of each segment. Labrum (Fig. 12A). Rectangular, length about 0.6 × maximum width; distal margin with small medial emargination, one row of robust, eventually pectinated, setae from lateral to middle of distal margin; one row of thin bifi d setae on distal margin not reaching distolateral margin; dorsal surface, near distal margin, with many thin setae over surface. Left mandible (Fig. 12B). Incisors partially cleft in two sets (fused at basal third); outer and inner set of incisors respectively with 4 + 3 denticles, outer incisor with a pectinated spine-like process; prostheca 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; mola with two large denticles,    inner larger than outer; outer margin convex. Right mandible (Fig. 12C). Incisors fused at base; outer and inner set of incisors respectively with 3 + 3 denticles and outer incisor with 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 seta; fi rst process of mola triangular, second expanded and straight; outer margin convex. Maxilla (Fig. 12D-E). Maxillary palp 1.6 × length of galea-lacinia; segment II 1.1 × length of segment I; segment II inner margin with small apical lobe; ventral canine enlarged, not laterally expanded; set of distal setae of inner-ventral row pointed. Hypopharynx (Fig. 12F). Lingua longer than superlingua, sub-quadrangular with small distomedial projection covered by tuft of simple setae, lateral area of distomedial projection excavated; superlingua with rounded outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Labium (Fig. 12G-I). Glossa slightly broad at base, distally rounded, shorter than paraglossa; inner margin with one row of spine-like setae starting at half length; ventral surface covered by thin setae; dorsal surface with inner arc with robust setae following inner-distal margin, outer arc at base following outer margin, at apex sinuous; one robust blunt seta on apex. Paraglossa curved inward; apex with two rows of robust and long spine-like setae; outer margin with three long thin setae; dorsal surface with three longitudinal rows of setae, fi rst near inner margin longer than half of length, distally with long robust setae and basally with long thinner setae; second with half of length of inner row, with robust long setae; and third with same length as second, distal setae long and robust, basal setae long and thin; ventral surface with one row of four setae near to ventral margin. Labial palp with segment I 0.6 × length of segments II and III combined; inner distal protuberance of segment II rounded, with almost straight distal margin, covered with thin setae; segment III conical, inner margin on basal half parallel to outer margin, distal half of inner margin slightly concave; outer margin with short thin setae, dorsal surface with one row of short spine-like setae near inner margin, ventral surface with one row of thin setae.

T
. Foreleg (Fig. 13A-C). Femur length about 3.7 × maximum width; dorsal and ventral margin with one row of long spine-like setae; anterior surface with one medial row of short blunt setae, one row of long spine-like setae near dorsal margin not reaching apex; posterior surface with one row of long spine-like setae near ventral margin reaching apex, and one medial row of long spine-like setae. Tibia. Dorsally bare; ventral margin with one row of long spine-like setae; patella-tibial suture absent. Tarsus. Ventral margin with one row of spine-like setae. Tarsal claws 0.4 × length of tarsus, with two rows of pointed denticles reaching apex. Hind leg (Fig. 13D-E). Femur dorsal and ventral margin with one row of long spine-like setae; anterior surface with one row of spine-like setae near dorsal margin, one row of long spine-like setae near ventral margin; posterior surface with one row of long 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 0.5 × length of tarsus, with two rows of pointed denticles reaching apex.

Rivudiva naia
Etymology ʻNaiaʼ in Amazonian folklore is the name of the native woman that, after being drowned by the enchantment of the god Moon, was transformed into a water star -Victoria Regia (Victoria amazonica (Poepp.) J.C.Sowerby). For this reason, the fragrant whitish fl owers of this plant only open at night. Name in apposition. H . Antenna. Flagellum with minute spines on apex of each segment. Labrum (Fig. 16A). Rectangular, length about 0.6 × maximum width; distal margin straight, one row of robust, eventually pectinated, setae from lateral to middle of distal margin; one row of thin bifi d setae on distal margin not reaching distolateral margin; dorsal surface, near distal margin, with many thin setae over surface. Left mandible (Fig. 16B). Incisors partially cleft in two sets (fused at basal third); outer and inner set of incisors respectively with 4 + 3 denticles; prostheca 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; mola with two large denticles, inner larger than outer; outer margin convex. Right mandible (Fig. 16C). Incisors fused at base; outer and inner set of incisors respectively with 3 + 2 denticles and outer incisor with spine-like process; prostheca stout, bifurcated at base, inner lobe longer than outer; 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 seta; fi rst process of mola triangular, second expanded and straight; outer margin convex. Maxilla (Figs 16D). Maxillary palp 1.8 × length of galea-lacinia; segment II 1.2 × length of segment I; segment II inner margin with large apical lobe; ventral canine enlarged, not laterally expanded; set of distal setae of the inner-ventral row pointed. Hypopharynx (Fig. 16E). Lingua longer than superlingua, sub-quadrangular with a small distomedial projection covered by tuft of simple setae; superlingua with truncate outer margin; short, thin, simple setae scattered over distal margin of lingua and superlingua. Labium (Fig. 16F-G). Glossa slightly expanded at base, distally rounded, shorter than paraglossa; ventral surface covered by thin setae; dorsal surface with inner arc with setae following inner-distal margin, outer arc at base following outer margin, slightly far from distal margin. Paraglossa curved inward; apex with one row of robust and long spine-like setae; outer margin with four long thin setae; dorsal surface with four longitudinal rows of setae, fi rst near inner margin longer than two third of length, distally with long robust setae and basally with long thinner setae; second with third of length of inner row, with robust long setae; and third with same length as second, distal setae long and robust, basal setae long and thin;   ventral surface with one row of fi ve 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 and projected to apex, covered with thin setae; segment III conical, apex broad pointed; outer margin with short thin setae, dorsal surface with one row of short spine-like setae near inner margin, ventral surface with one row of thin setae.

T
. One mark on mesothorax. Foreleg (Fig. 17A-C). Femur length about 2.9 × maximum width; dorsal and ventral margin with one row of long spine-like setae; anterior surface with one medial row of short setae, one row of blunt setae near dorsal margin not reaching apex; posterior surface with one row of long spine-like setae near ventral margin reaching apex, and one medial row of long spine-like setae. Tibia. Dorsally bare; ventral margin with one row of long spine-like setae; patella-tibial suture present. Tarsus. Ventral margin with one row of spine-like setae. Tarsal claws 0.4 × length of tarsus, with two rows of rounded denticles at basal half. Hind leg (Fig. 17D-E). Femur dorsal and ventral margin with one row of long spine-like setae; anterior surface with one row of spine-like setae near dorsal margin, one row of long spine-like setae near ventral margin; posterior surface with one row of spine-like setae near ventral margin at basal half. Tibia. Dorsally bare; ventral margin with one row of small spine-like setae; patella-tibial suture present. Tarsus. Ventral margin with one row of small spine-like setae. Tarsal claws 0.5 × length of tarsus, with two rows of rounded and small denticles reaching apex.

A
. Terga (Fig. 18E) with all segments white (color lost in alcohol), tergum IV with one medialred mark; tergum V with one large medial red mark; tergum IX with one red mark near lateral margin. Posterior margin of terga with small triangular blunt spines (Fig. 18A). Gills oblong, longer than next segment, with one medial trachea red pigmented. Paraproct (Fig. 18B) with two marginal spines, posterolateral extension with spines. Cerci (Fig. 18C) with lateral spines on every segment. Paracercus (Fig. 18D) without spines.

Comments
In Boldrini et al. (2012), this unidentifi able specimen was named as R. trichobasis. The specimens studied are in bad condition, with essential structures broken and missing, such as head, labium, hypopharynx, part of maxilla and abdomen. However, based on the maxillary palp, it is probably a new species.

Discussion
Study of the paratype and four of the six offi cial records of R. trichobasis (Lugo-Ortiz & McCaff erty 1998;Cruz et al. 2011;Falcão et al. 2011;Boldrini et al. 2012;Boldrini & Cruz 2014), under the new perspective (Cruz et al. 2018;Salles et al. 2020), corroborated the initial hypothesis that the lack of information resulted in a broad diagnosis of the species, causing the assignment of diff erent species to a single name.
The change in species concept, from a single species with a wide distribution and morphological plasticity to a group of closely related species, is well grounded in morphology. The evidence here presented demonstrates clearly that 'R. trichobasis Lugo-Ortiz & McCaff erty, 1998ʼ is, in fact, a complex of species. In parallel to morphology, a molecular approach would have strengthened the status and validity of the diff erent species. We hope that this approach will be possible in the near future.
The change in species concept does not interfere with the inclusion of the genus in the subfamily Baetinae (sensu Cruz et al. 2021) [= Baetovectata Kluge & Novikova 2011, and in the generic delimitation proposed by Cruz et al. (2018) and Salles et al. (2020). However, amendments need to be made. All species present ventral canine of the maxilla expanded, laterally folded over canines only in R. inma Salles & Nieto in Salles et al., 2020 and R. trichobasis. In all species the distal dentiseta is canine-like, while the other dentisetae are seta-like; and the distal setae on the inner-ventral row of the maxilla bend over the canines.
The trichobasis group is mainly characterized by spine-like setae on the scape and pedicel. This group could be related to R. oonirikoperi based on the presence of spine-like processes on the outer margins of the mandibular incisors : fi gs 12-13), glossa not expanded at base and apically rounded (Salles et al. 2020: fi g. 16), hindwing pads absent, and the presence of robust apically pointed setae on abdominal sterna : fi gs 36-37). Additionally, R. oonirikoperi and the trichobasis group also share arcs of setae on glossa close to inner and outer margins, and groups of setae on the legs. The minantenna group (R. minantenna + R. inma) is characterized by glossa with base expanded and apex obliquely truncate : fi g. 6), hind wing pads present, and abdominal sterna with simple setae . Additionally, both species share outer arc of setae on glossa moved to inner margin. The hypothesis of groups has not yet been tested, Cruz et al. (2018Cruz et al. ( , 2021 included R. minantenna and R. trichobasis in the cladistic analyses, the two species known by their nymphal stage at that time. Salles et al. (2020), based on geographic distribution, discussed the possibility of R. oonirikoperi being, in fact, the nymphal stage of Rivudiva venezuelensis (Traver, 1943). However, in R. venezuelensis characteristics such as turbinate eyes circular, body pigmentation pattern without typical marks on segments II, III and VI, and gonovectis V-like, deep in segment IX, are similar to Paracloeodes, and not to Rivudiva. Using the proximity criteria, R. minantenna could also be the nymphal stage of R. coveloae (Traver, 1971). Rivudiva coveloae is likely to belong to Rivudiva due to its having hind wings, oval turbinate eyes and sinuous gonovectis not deep in segment IX; on the other hand, the pigmentation patterns of the abdomen are not the typical marks on segments II, III and VI. It is not possible to resolve these doubts based on the evidence presented here.
In conclusion, there were six species under the name 'trichobasis', fi ve of them properly redescribed or described here. We recommend the evaluation of unreviewed records using the new morphological evidence presented herein, as well molecular studies.