Generic revision of Argiolestidae (Odonata), with four new genera

The subfamily Argiolestinae is raised to family level to include all zygopteran genera in which the gills of the larvae are flat and held in a horizontal plane. A diagnosis of the family is given and characters for both adults and larvae are presented. The family is divided into two subfamilies based on characters in the genital ligula, with the subfamily Argiolestinae found in Australasia east of Huxley's Line and the subfamily Podolestinae found in Africa and Asia west of Huxley's Line. Four genera are newly described: Eoargiolestes (New Caledonia, type species Sympecma ochracea Montrouzier, 1864), Luzonargiolestes (Philippines, type species Argiolestes realensis Gapud & Recuenco, 1993), Solomonargiolestes (Bougainville, Papua New Guinea and Malaita, Solomon Islands, type species Argiolestes bougainville Kalkman, 2008) and Pyrrhargiolestes (Papua New Guinea, type species Argiolestes sidonia Martin, 1909). In addition Metagrion (type species Argiolestes postnodalis Selys, 1878) and Wahnesia (type species Argiolestes kirbyi Forster, 1900), two genera not in use for over 70 years, are reinstated. Based on molecular data the African genera Neurolestes and Nesolestes have been shown to be good genera and are here treated as such, Nesolestes nigeriensis is transferred to Neurolestes. All 20 genera included in Argiolestidae are discussed, with type species, key characters of adults, distribution and habitat being given. In addition a diagnosis is presented for each genus and information is given on their identification together with a map of the distribution of the genus and scanning electron microscope images of the genital ligula of most genera. A key to the genera of the Australasian region is presented and keys to the species of Caledargiolestes, Caledopteryx and Podopteryx are given. New distributional records of Caledargiolestes, Caledopteryx, Luzonargiolestes, Solomonargiolestes and Podopteryx are provided.