The forest microhabitat distribution of overwinteringApanteles melanoscelus(Ratzeburg) was assessed by sampling live and dead trees and small ground plots. The logarithm of the average number of cocoons per lowest 2 m of dead tree or stump was used to predict cocoon population densities. Extensive sampling during fall and winter, laboratory rearing and dissection of collected cocoons, and partial correlation analysis showed that mortalities caused by some hyperparasites were negatively correlated with each other, suggesting competition between them. Multiple regression analysis demonstrated that the mortality caused by someA. melanoscelushyperparasites [Eurytoma appendigaster(Swederus) (Hymenoptera: Eurytomidae) and Eulophidae spp.] varied in a positive, density-dependent manner with differences inA. melanosceluscocoon numbers. Such information is useful in suggesting which hyperparasites are important so that research on decreasing their impact onA. melanosceluspopulations can be done.