Faunistic and taxonomic investigations on the Odonata fauna of the Samoan archipelago with particular focus on taxonomic ambiguities in the “Ischnurine complex”

New faunistic data is provided on the Odonata inhabiting the three main islands within the Samoan archipelago, namely Savai’i, Upolu and Tutuila as well as the smaller islands of Aunu’u and the Manu’a group. The specimens collected or observed in the field were compared to samples from other nearby Pacific island groups such as Fiji and Tonga. This study makes important contributions towards resolving taxonomic issues regarding the Ischnura species described as endemic to Samoa and their relations to other Coenagrionidae genera. New diagnostic features for distinguishing between females of the endemic genera Amorphostigma and Pacificagrion, subspecies separation in the Pacific Tramea transmarina and distinguishing between Samoan Hemicordulia species are suggested. Anaciaeschna melanostoma is proposed as junior synonym of A. jaspidea. A possible new subspecies of Lathrecista asiatica, confined to the Samoan archipelago, is discussed. The validity of Agriocnemis interrupta as a separate species from A. exsudans is questioned. Pacific Pseudagrion is believed to be represented within the region by one species only, with separate subspecies in Fiji, Tonga and Samoa, although more specimens from Fiji are required to resolve this issue.