Multi-Species Host Use by the Parasitoid Fly .

Antagonistic species relationships such as parasitoid/host interactions lead to evolutionary arms races between species. Many parasitoids use more than one host species, requiring the parasitoid to adapt to multiple hosts, sometimes being the leader or the follower in the evolutionary back-and-forth between species. Thus, multi-species interactions are dynamic and show temporary evolutionary outcomes at a given point in time. We investigated the interactions of the multivoltine parasitoid fly that uses different katydid hosts for each of its fly generations sequentially over time. We hypothesized that this fly is adapted to utilizing all hosts equally well for the population to persist. We quantified and compared the fly's development in each of the four hosts. Cumulative parasitism rates ranged between ~14% and 73%, but parasitoid load and development time did not differ across host species. Yet, pupal size was lowest for flies using as a host compared to and other host species. Successful development from pupa to adult fly differed across host species, with flies emerging from displaying a significantly lower development success rate than those emerging from and the other two hosts. Interestingly, and did not differ in size and were smaller than and hosts. Thus, utilized all hosts but displayed especially low ability to develop in , potentially due to differences in the nutritional status of the host. In the multi-species interactions between the fly and its hosts, the poor use of may currently affect the fly's evolution the most. Similarities and differences across host utilization and their evolutionary background are discussed.