Meeting Abstract
All animals have to find resources in their environments. For insect parasitoids, this problem is challenging because they must not only find food and mates but also suitable hosts. Like all animals, hosts emit olfactory cues into the environment. Additionally, because hosts are often herbivorous insects, the olfactory cues of the host plant can also be used parasitoids for tracking hosts. In many systems, it is unclear which (if any) type of olfactory cues parasitoids use, and whether or not scent use is a learned or innate behavior. Here, we examine a tri-trophic interaction between the broad-leafed desert perennial Datura wrightii, its main herbivore in southeastern Arizona (caterpillars of Manduca sexta), and two groups of parasitoids that attack M. sexta (wasps that are egg parasitoids and flies that are larval parasitoids). In both groups of parasitoids, we tested whether insects found their hosts using olfactory cues emitted by the host or olfactory cues emitted by the plant on which the host is feeding. We show that tachinid flies were attracted to olfactory cues generated by M. sexta frass (a combination of both host and plant olfactory cues), and that Trichogramma wasps preferentially moved towards Datura plants that were attacked by M. sexta. Furthermore, Trichogramma were capable of learning olfactory cues as adults. Finally, we show that parasitized caterpillars ate less, grew slower, and left the plant at lower body mass, indicating that parasitization benefits the plant.
