The Nerthra alaticollis species-group is defined as a monophyletic group on the basis of wing and genitalic characters. Two new species are described: Nerthra appha n. sp. and N. polhemi n.sp. Nerthra membranacea Nieser is recognized as a junior synonym of N. adspersa. Nerthra tuberculata (Montandon) and N. praecipua Todd are removed from the alaticollis species-group. Nine species are assigned to the species-group, and all species are described with illustrations. A phylogeny of species is provided.

A total of 173 species of mayflies, representing 15 families and 45 genera, are reported from the state of New York. First state records for 43 species and 891 new county reports for 129 species are included. Previously published reports are summarized, and pertinent remarks on species are annotated. The occurrence of Dannella provonshai, Heptagenia julia, and Plauditus gloveri in New York represent significant range extensions. The discovery of Epeorus frisoni in New York represents only the second report of the species. Species potentially of environmental concern are noted.

The genus Ptilomera is revised for New Guinea and nearby islands. Four previously described taxa are redescribed and discussed: P. aello Breddin, P. papuensis Hungerford & Matsuda, P. breddini Hungerford & Matsuda, and P. cheesmanae Hungerford & Matsuda, the latter newly elevated from subspecies to full species rank. Eighteen new species are described as follows: P. waigeo from Waigeo Island, P. misoolensis from Misool Island, P. yapenana from Yapen Island, P. arfak from the Vogelkop Peninsula of Irian Jaya, P. timika from southern Irian Jaya, P. etna from western central Irian Jaya, P. iriana from north central Irian Jaya, P. wapoga from north central Irian Jaya, P. kiunga from southwestern Papua New Guinea, P. omo from southern central Papua New Guinea, P. kutubu from the southern highlands of Papua New Guinea, P. jimi from the central highlands of Papua New Guinea, P. wewak from northern Papua New Guinea, P. morobe from northeastern Papua New Guinea, P. biroi from northeastern Papua New Guinea, P. insularis from Umboi Island, P. novabrittanica from New Britain, and P. bismarckensis from New Ireland. Keys to all species occurring in the New Guinea region are provided for both males and females, accompanied by range maps, and figures of the male genitalic complex, male parameres, male endosoma, and female terminal abdomen in lateral view.

A new Mexican species of Ceraspis Serville from Oaxaca state is described and illustrated. A key to the known Mexican species of this genus is included.

The genera Praocidia Fairmaire and Pilobaloderes Kulzer (Pimeliinae: Praocini), distributed in the Andes of northern Peru, are revised. Both genera are transferred from the Nycteliini to Praocini on the basis of new tribal level characters. Character states of Praocidia and Pilobaloderes shared with the other genera of Praocini and not shared with genera of Nycteliini are discussed. Redescriptions of the genera, their three species, keys, habitus photographs and illustrations of body and male genitalia are included.