Eumerus purpurariae, described from the Canary Islands (Atlantic), has been reared from the stems (platyclades) of the cactus Opuntia maxima (the first known host) on Nueva Tabarca, a Mediterranean island close to the Iberian coast. The egg, larva and puparium of E. purpurariae, as well as its life cycle on the above host-plant are described. The feeding behaviour of the larva in relation to the cephalopharyngeal skeleton morphology is analysed. Based on the present data, comparative table containing the main morphological characteristics of the injurious Eumerus species of the Palaearctic region is presented.