Parasitoid lifespan is influenced by nutrient availability, thus the lifespan of parasitoids that rely on their hosts for nutritional resources (either via host feeding or by consuming honeydew) should vary with host density. We assessed the survival and reproduction of one such species, Aphelinus certus—a parasitoid of the soybean aphid, Aphis glycines—over a range of host densities using a laboratory assay. We found a positive, asymptotic relationship between host density and the lifespan and fecundity of A. certus that was supported by a traditional survivorship analysis as well as a logistic model. Parasitoids from this assay were also used to develop a wing wear index relating setae damage to parasitoid age. This index was used to estimate the life expectancy of field-collected parasitoids, which was shorter than the life expectancy of laboratory-reared female parasitoids. Finally, host-density-dependent parasitoid lifespan was incorporated into a coupled-equations matrix population model that revealed that decreasing the degree of host density dependence leads to higher equilibrium host densities and changes in the quality of equilibrium (e.g. stable limit cycles). These results detail the relatively unstudied phenomenon of host-density-dependent parasitoid lifespan and suggest that differences between laboratory- and field-determined parasitoid life expectancy have important implications for population dynamics and the biological control of insects.

寄生虫的寿命受养分供应量的影响，因此，依赖寄主获取营养资源（通过寄主喂养或食用蜜露）的寄生虫的寿命应随寄主密度的变化而变化。我们使用实验室测定法评估了一种这样的物种在不同的宿主密度范围内的存活和繁殖情况，即Aphelinus certus（大豆蚜虫的一种寄生虫），Aphis甘氨酸。我们发现寄主密度与A. certus的寿命和繁殖力之间呈正的渐近关系传统的生存分析和逻辑模型都支持这一点。来自该测定法的寄生物也被用于建立机翼磨损指数，其将刚毛损伤与寄生物年龄联系起来。该指数用于估计野外采集的寄生虫的预期寿命，该寿命比实验室饲养的雌性寄生虫的预期寿命短。最后，将依赖于宿主密度的寄生虫的寿命纳入耦合方程矩阵种群模型，该模型表明降低宿主密度依赖性的程度会导致较高的平衡宿主密度和平衡质量的变化（例如，稳定的极限环）。