Cost of parasite exposure depends on host ontogeny

Abstract Parasite exposure can lead to non‐consumptive effects (NCEs) in hosts and research in this area has thus far focused primarily on exposure at the developmental stage known to be infected. Using the Drosophila nigrospiracula‐Macrocheles subbadius system, we investigated the impact of parasite exposure at two stages undergoing major developmental changes and/or metamorphosis but not known to be infected (i.e., egg and pupae). Drosophila eggs were exposed to parasites indirectly (caged mites) or directly (free‐roaming mites) to test the effects of exposure on egg hatching success and larval development. We then investigated whether M. subbadius can utilize the fly pupae as a resource by measuring host emergence success and mite survival when provisioned with a pre‐pharate or post‐pharate pupa. We found that eggs in direct contact with mites had an 87% decrease in hatching success compared to unexposed eggs. However, indirect exposure had no effect on hatching success. We also found direct exposure to mites resulted in a 43% reduction in emergence among pre‐pharate pupae compared to post‐pharate pupae. On average, there was a 69% reduction in mite longevity when offered pupae or water compared to a fly host, suggesting mites cannot parasitize pupae. These results highlight the importance of accounting for host ontogeny as non‐consumptive effects may be stage‐specific; otherwise, we may be mischaracterizing the total impact of parasite exposure.