We present a taxonomic and biological study of the genus Eurytoma Illiger, 1807 (Hymenoptera, Eurytomidae), based on the morphology and biology of the terminal-instar larvae of 13 species living as parasitoids in the galls of European species of cynipid gall wasps. We provide the first detailed descriptions of the terminal-instar larvae of the studied species, illustrating diagnostic characters for the family and the studied genera with SEM pictures. We also provide a species key for the identification of Eurytoma larvae associated with cynipid galls, based on particular characters associated with the head, mouthparts and mandibles. Although we find only limited informative variation in body shape, the head and mandibles provide many characters of potential taxonomic and phylogenetic value. We summarise the larval biology of the 13 Eurytoma species inhabiting cynipid galls. Eurytoma larvae are usually solitary idiobiont ectoparasitoids of the host larva or of larvae of cynipid inquilines that also often feed on gall tissue.
Insecta, Hymenoptera, Chalcidoidea, Eurytomidae, Eurytoma, larva, parasitoids, cynipid galls, identification keys.