Chemical information from the fungus Amylostereum areolatum and host-foraging behaviour in the parasitoid Ibalia leucospoides

Abstract.  Parasitoids locate hosts using reliable and predictable cues such as smells derived from host plants or from the hosts themselves. For host species that live with mutualistic organisms, such as several wood boring insects, cues derived from the symbionts are likely to be exploited by specific parasitoids. Through a set of bioassays, the behaviour of the parasitoid Ibalia leucospoides Hochenwarth (Hymenoptera: Ibaliidae) is studied in response to the fungus Amylostereum areolatum Boidin (Basidiomycotina: Corticiaceae), a symbiont of its host, the wood wasp Sirex noctilio Fabricius (Hymenoptera: Siricidae). The results show that parasitoids are attracted to the fungus when growing naturally within pine logs, and also when growing on an artificial medium. Fungal volatiles also elicit increased parasitoid activity and may provide information on relative densities of hosts available for parasitization. It is speculated that the the chemical information derived from the host fungal symbiont comprises reliable and detectable host-locating cues used by parasitoids to search for concealed hosts.