Larval parasitoids of frugivorous Drosophila as well as related parasitoid species that attack Drosophila or Fannia species in mushrooms use water soluble larval kairomones in host location. Parasitoids of fungivorous flies allocate more searching time to patches containing a filtrate of mushrooms infested with host larvae compared to patches with a filtrate of uninfested mushrooms. Filtrates of mushrooms infested with a non-host species do not increase their searching time. Studies with parasitoids of frugivorous Drosophila showed that the ability to recognize kairomone is acquired through learning. Females without oviposition experience do not respond differently to patches with and without kairomone. Parasitoids that had learned the kairomone of one drosophilid host species also recognized the kairomone of another host species, which suggests that kairomones from Drosophilidae may be similar.