The relative contributions of time and eggs to the cost of reproduction

Whether the trade-off between current and future reproduction in insect par asitoids is mediated by the costs of time or eggs remains an issue of conte ntion. Life-history models predict that parasitoids have some risk of exhau sting their lifetime supply of oocytes. I develop a simple conceptual model that assesses the relative contributions of time and eggs to the cost of r eproduction by placing them in a common currency: foregone future fitness r eturns. Although rates of egg limitation observed in nature are modest, egg s still often make the dominant contribution to the overall cost of oviposi tion. Therefore, models of parasitoid reproduction must recognize the costl iness of both time and eggs.