Acerpenna

Abstract: Considerable nomenclatural revision of the North and Middle American Baetidae has resulted from comprehensive research aimed at formulating a phylogenetic classification. The 17 Nearctic species in Pseudocloeon not previously assigned to Acentrella or Apobaetis are newly placed in Baetis or Barbaetis. Cloeon in the area is restricted to C. cognatum, while two species previously in Cloeon are placed in Centroptilum and nine in Procloeon, a genus considered for the first time in the Nearctic. Definitions of Centroptilum and Procloeon are modified, both now incorporate species with hindwings and species without hindwings, and 19 species are transferred from Centroptilum to Procloeon. Pseudocentroptilum s. auctt. in North America is synonymized with Procloeon. Neocloeon is recognized as a synonym of Centroptilum s. str. and removed from synonymy with Cloeon. Dactylo baetis is placed in synonymy with Camelobaetidius, and all species, including those from South America, are newly combined. Two species of Baetis are transferred to Acerpenna, and two to Fallceon. A checklist includes 154 currently recognized species among 19 genera in the area, and incorporates 21 new species synonyms and 57 new combinations. The names Baetis armillatus and Baetis cinctutus are substituted for Pseudocloeon parvulum and Pseudocloeon cingulatum, repec tively, which otherwise attain homonymie status. Regional distributions for each species and abbreviated synonymies since 1976 are annotated to the checklist. Brief discussions of each genus include information on species diagnosis, revisionary bases, status, and needs. A guide to all nomenclatural changes and added taxa since 1976 provides the bibliographic sources of all such information and serves as a ready index to name equivalencies resulting from extensive recent and present revisions.

Abstract: Americabaetis (Insecta: Ephemeroptera: Baetidae), previously considered synonymous with Acerpenna, is reinstated and given generic rank. The genus differs from Acerpenna in lacking hindwings, gills on abdominal segment 1, and a conical process between the male genital forceps, and in possessing apically rounded gills on abdominal segment 7. The genus has a general Neotropical distribution with a northern limit in east-central Mexico. Five new species of Americabaetis are described from South America: A. alphus, new species, from Argentina, Bolivia, Brazil, Chile, and Paraguay; A. labiosus, new species, from Brazil, Paraguay, and Uruguay; A. longetron, new species, from Brazil, Paraguay, and Uruguay; A. maxifolium, new species, from Paraguay; and A. titthion, new species, from Brazil. Americabaetis boriquensis, new combination; A. intermedius, new combination; A. naranjoi, new combination; A. pleturus, new combination; and A. robacki, new combination, are reviewed.

Abstract: 1. Streams in the seasonal wet and dry tropics have highly dynamic discharge regimes. Our study stream, located in mid-western Brazil, drains into the Pantanal, South America’s largest wetlands, and is characterized by frequent spates in the rainy season and several weeks of interrupted flow in the dry season. 2. In order to understand how these seasonal flow patterns influence the aquatic fauna, floating litter was studied because: (i) this habitat is exposed to the current, and thus is likely to be most affected abiotically and biotically by changes in flow; and (ii) this habitat is abundant in unaltered tropical streams. Studies were conducted in a thirdand a fourth-order reach. Mayflies were chosen as study organisms because they were frequent and species-rich on floating litter, and because they should to be responsive to changes in current velocity. 3. In the course of 15 months, covering one rainy and two dry seasons, mayflies showed pronounced seasonal patterns at family and genus level, which were evidently driven by discharge. Two periods of high mayfly densities were observed in the course of one year. One maximum coincided with the peak of the rainy season, the other with the peak of the dry season, and both were distinct in faunistic composition. At high current velocities the leptophlebiid Farrodes sp. was dominant and Leptohyphes sp., Acerpenna sp. and Paracloeodes sp. were frequent. In the dry season, when the river was reduced to isolated standing waters, 86‐93% of all mayflies were Caenis sp. 4. Altogether sixteen mayfly genera from the families Baetidae, Caenidae, Leptohyphidae, Leptophlebiidae and Oligoneuriidae were recorded. Two genera are new to science, the baetid Aturbina was recently described (among others, from material from our study river), Acerpenna and Paracloeodes are new records for South America, and Miroculis and Terpides are recorded for the first time south of the Amazon.

Abstract: The genus Acerpenna (Ephemeroptera: Baetidae), previously known from North America north of Mexico, is shown to occur extensively in Latin America, where it demonstrates considerable variability. The genus includes species with or without hindwings, with or without gills on abdominal segment 1, and with gills on abdominal segment 7 either rounded or pointed apically. Americabaetis, originally considered a subgenus of Baetis s. 1. and having one nominal species described from Cuba, is synonymized with Acerpenna. Besides A. naranjoi (Kluge), n. comb., four new species of Acerpenna are described from Latin America: A. boriquensis, n. sp., from the Greater Antilles, A. intermedia, n. sp., from Central America, A. pletura, n. sp., from Central America and Mexico, and A. robacki, n.sp., from South America.

Abstract: siilfurosiis (Day), comb, n.], not Baetis Leach. Among North American Baetidae fauna only the species of Acerpenna possess the following combination of features: forewings with double marginal intercalaries; relatively narrow hindwings, with an undulate costal border and often three longitudinal veins; a male subgenital plate roughly in the form of a conical process (difficult to see in older specimens); and elongate apical segment of the male forceps (Waltz and McCafferty 1987). Acerpenna siilfurosiis is consistent in all features outlined above and is therefore transferred from Baetis to Acer-