The sawfly genus Heterarthrus is naturally distributed in the Palaearctic, with a single described Oriental species. Their larvae mine in the leaves of trees and shrubs of Salicaceae, Betulaceae, and Sapindaceae ( Acer). We here recognise twelve West Palaearctic species as valid, with the status of two additional nominal species group taxa in need of further study: fruticicolum Ermolenko, and smithi Ermolenko. A key to adults of the species occurring in the West Palaearctic is presented. Two new species are described: Heterarthus vikbergi Liston, Mutanen & Viitasaari, sp. nov. from females and males reared from leaf-mines in Populus balsamifera collected in eastern Finland, and Heterarthrus fiora Liston, sp. nov. from females reared from Acer pseudoplatanus. The latter is a widespread European species, previously misidentified as Heterarthrus aceris (Kaltenbach, 1856). New junior subjective synonyms are Phyllotoma aceris Kaltenbach, 1856 of Heterarthrus leucomela (Klug, 1818), H. aihinoensis Haris, 2006 of H. kamtchaticus (Malaise, 1931) sp. rev., and H. imbrosensis Schedl, 1981 of H. wuestneii (Konow, 1905). Lectotypes are designated for Phyllotoma flavicollis Gussakovskij, 1947, P. kamtchatica Malaise, 1931, and Tenthredo ochropoda Klug, 1818.