Abstract – A new species of Isocolus Förster (Hymenoptera, Cynipidae “Aylacini”) is described from
Spain: Isocolus leuzeae n. sp.The new species induces galls in flower heads of Leuzea conifera (Asteraceae)
and represents the first known aylacin species associated with this plant. The species is closely related
to Isocolus lichtensteini (Mayr) that induces galls on stems of Centaurea aspera. Biological data on its life
cycle, larva and gall are provided