We report on a five-year investigation of the complex of parasitoids associated with coexisting populations of Euphydryas aurinia and Euphydryas desfontainii at a Spanish site. A sample of over 7000 eggs, 1000 larvae and 200 pupae (the last of these in part having been experimentally placed) revealed the existence of no egg parasitoids, of three primary larval parasitoids and of five primary pupal parasitoids, plus 13 secondary and facultatively tertiary parasitoids associated with the cocoons of the main larval parasitoid, the specialist Cotesia sp. D. The most abundant secondary parasitoid, Neochrysocharis albiscapus, entirely escaped tertiary parasitism by being gregarious. The mortality induced by parasitoids on the butterfly populations, although heavy, was clearly partially minimized by secondary parasitoids acting on Cotesia sp. D. The striking coincidence of the parasitoid complexes attacking the two Euphydryas species suggests a good system for investigating apparent competition between hosts sharing common natural enemies.
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