Parasitism and Host-Location Preference in Habrobracon hebetor (Hymenoptera: Braconidae): Role of Refuge, Choice, and Host Instar

International audiencePlodia interpunctella (Hü bner) (Lepidoptera: Pyralidae) is a cosmopolitan insect infesting a broad range of commodities, including raw or processed cereal. It has a high fecundity and short generation time, making it a useful tool in testing hostÐparasitoid hypotheses. The current study examined the interactions between trophic levels during parasitism and host location by Habrobracon hebetor Say (Hymenoptera: Braconidae) within a closed environment by carrying out multiple tests to evaluate the role of refuge and host instar, on the mortality of P. interpunctella and on the emergence of H. hebetor. Results showed that H. hebetor was able to parasitize all instars (Þrst through fourth) of P. interpunctella, but signiÞcantly fewer early instars (Þrst through fourth) were parasitized. Parasitized third and fourth instars were more proÞtable to H. hebetor, irrespective of refuge or choice factors, as signiÞcantly more adult parasitoids emerged from third and fourth instars. H. hebetor females consistently showed a preference for fourth instars of P. interpunctella when they were offered a choice between early and late host instars in arenas both with and without a refuge. Generally, parasitization of early instars was higher in no-choice than in choice tests. The behavior of H. hebetor in relation to host choice and its inßuence on the pest mortality are discussed