Does parasitoid attack strategy influence host specificity? A test with New World braconids

Abstract. 1. Parasitoid attack strategy has been divided into two broad categories, koinobiosis and idiobiosis, based on the arrest of host development and the intimacy of larval contact. Koinobionts allow the host to continue developing and larvae usually feed within the host body, whereas idiobionts stop host development and larvae usually feed externally. 2. Comparisons of host ranges from rearings of parasitoids from specific host communities have shown that koinobionts are more host specific than idiobionts. These tests suggested that parasitoid attack strategy influenced specialisation in parasitoid–host interactions within certain host communities. 3. To determine whether this pattern was consistent within a single parasitoid lineage that utilises hosts from many different communities, the host ranges of koinobiont and idiobiont braconid genera of the New World were compared. Koinobiont genera utilised fewer host families than idiobionts, suggesting that parasitoid attack strategy may direct the evolution of host specificity throughout the evolutionary history of parasitoid lineages.