Resource competition affects developmental outcomes of the acoustic parasitoid fly <i>Ormia ochracea</i>

Abstract In parasitoid systems, resource competition can significantly impact developmental outcomes. This study investigates how larval competition and host characteristics influence development in the acoustic parasitoid fly Ormia ochracea, using the house cricket Acheta domesticus as a host. We experimentally manipulated larval load (1 vs. 2 larvae per host) and recorded host sex and size to assess their effects on pupation and eclosion (adult hatching) success, as well as pupal and adult fly size. While double infestations increased total yield (0.78 vs. 0.54 flies per host), larvae developing without competition exhibited higher relative pupation and eclosion success and produced larger pupae and adult flies, indicating greater individual fitness. Although female host crickets yielded larger pupae, resource competition was the dominant factor shaping developmental outcomes. These results highlight the trade-offs between reproductive yield and offspring fitness driven by resource competition and validate the commercially available A. domesticus as a viable host.