We investigated the metapopulation genetic structure of two specialist parasitoids, Cotesia melitaearum and Hyposoter horticola, attacking the Glanville fritillary butterfly (Melitaea cinxia) in the Aland Islands south-western Finland. The host butterfly persists as a classic metapopulation in a network of 4,000 small habitat patches within an area of 50 by 70 km . The two parasitoids are known to differ greatly in their population dynamics and spatial pattern of occupancy in local host populations. Analysis of genetic population structure using FST and clustering of multilocus genotypes revealed a distinct large-scale spatial structure in C. melitaearum but a very weak pattern in H. horticola. This result is consistent with the known difference in the dispersal range (much longer in H. horticola) and population size (much greater in H. horticola) of the two parasitoids. Melitaea cinxia (Nymphalidae) : Host Cotesia melitaearum (Braconidae) : Parasite Hyposoter horticola (Ichneumonidae) : Parasite Genetics; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Ecology; Land zones; Palaearctic region; Eurasia; Europe Cotesia melitaearum; Hyposoter horticola; Population genetics; Metapopulation genetic structure; Lepidopteran hosts; Metapopulation genetic structure in coexisting parasitoid species; Melitaea cinxia; Distribution within habitat; Dispersal patterns; Finland; Aland Islands Melitaea cinxia; Hymenopteran parasites; Metapopulation genetic structure in coexisting parasitoid species; Cotesia melitaearum & Hyposoter horticola; Finland; Aland Islands none