An integrated taxonomic revision of Ctonoxylon (Coleoptera, Curculionidae, Scolytinae) reveals new Malagasy species originating from multiple recent colonisations of the island.

Ctonoxylon is a strictly Afrotropical genus of bark beetles breeding under bark of rainforest trees and lianas. A taxonomic revision of the genus included a molecular phylogenetic analysis of ten species based on three gene fragments and was compared to a morphology-based tree topology for all 24 currently recognised species. Four species are described as new to science: Ctonoxylontorquatum , sp. nov. , Ctonoxylontuberculatum , sp. nov. , Ctonoxylonquadrispinum , sp. nov. , all from Madagascar, and Ctonoxylonpilosum , sp. nov. from Cameroon. Ctonoxylonhirsutum Hagedorn, 1910, stat. rev . is resurrected from synonymy with C.flavescens Hagedorn, 1910, and C.atrum Browne, 1965 stat. rev. from its synonymy with C.methneri Eggers, 1922 (as C.hamatum Schedl, 1941). The following species have new synonymies suggested: Ctonoxylonfestivum Schedl, 1941 (= C.dentigerum Schedl, 1941, syn. nov. ), C.methneri Eggers, 1922 (= C.hamatum Schedl, 1941, syn. nov. , = C.griseum Schedl, 1941, syn. nov. ), C.montanum Eggers, 1922 (= C.longipilum Eggers, 1935, syn. nov. , = C.nodosum Eggers, 1940, syn. nov. ), C.camerunum Hagedorn, 1910 (= C.conradti Schedl, 1939, syn. nov. ), and C.spinifer Eggers, 1920 (= C.setifer Eggers, 1920, syn. nov. ). New country records are noted for C.festivum (Tanzania), C.flavescens (Uganda), C.camerunum (Liberia), C.crenatum Hagedorn, 1910 (Democratic Republic of the Congo), C.spathifer Schedl, 1941 (Ghana), C.atrum (Cameroon), and C.spinifer (Madagascar), with patterns in distribution and colonisation of Madagascar discussed. An identification key with pictures of all species is provided.