On two unjustified rankings of Pacific Odonata (Insecta)

Modifications of nomina proposed for two Pacific Odonata taxa are found to be unsubstantiated. Each has been proposed without the support of taxonomic studies. Herein, it is demonstrated that the raising of the subgenus Adversaeschna Watson, 1992 to genus rank and subsuming the genus Amorphostigma Fraser, 1925 to Ischnura Charpentier, 1840 are not justified. The first, Adversaeschna, was a mistake introduced and multiplied widely in nomenclature lists adopted by online databases and other studies. The second, Amorphostigma, was based on premature information to propose a plausible taxonomy of a diverse Pacific clade which most likely consists of several taxa deserving of separate generic ranks, supported by preliminary phylogenetic work. Therefore, these nomina should be reverted to reflect current taxonomic revisions. Adversaeschna should be considered as a subgenus of Aeshna Fabricius, 1775 and Amorphostigma as a nomen of generic rank.