Melitaea cinxia; FOOD-PLANTS; Plantago lanceolata & Veronica spicata; Plant use patterns, hymenopteran parasitoid occupancy implications; FOOD-AVAILABILITY; Food plant aggregations, distribution relationships; HYMENOPTERAN-PARASITES; Cotesia melitaearum; Parasite colonization & extinction, effects of host diet & range; TROPHIC-STRUCTURE; Tritrophic system; Plant host use effects on hymenopteran parasitoid occupancy; POPULATION-SIZE; Group size, isolation & dietary relationships; DISTRIBUTION-WITHIN-HABITAT; Isolation, group size & dietary relationships; Implications for hymenopteran parasitoid colonization & extinction; FINLAND-; Aland Islands; Range & diet, effects on hymenopteran parasite extinction & colonization Cotesia melitaearum; LEPIDOPTERAN-HOSTS; Melitaea cinxia; Parasite colonization & extinction, impact of host diet & range; TROPHIC-STRUCTURE; Tritrophic system, effects of lepidopteran host diet & range; POPULATION-DYNAMICS; Local extinction & colonization patterns; Effects of lepidopteran host population size, isolation & diet; HABITAT-COLONIZATION; Effects of host diet & range; FINLAND-; Aland Islands; Extinction & colonization, effect of lepidopteran host diet & range, larvae