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When two parasitoids exploit a common host simultaneously, competitive interactions between them usually occur, and are more complex among host-killing species. Diglyphus isaea (Walker) and Neochrysocharis formosa (Westwood) are larval parasitoids of agromyzid leafminers. They have widespread distributions and share the same host resources when sympatric. In this study, interactions between these two parasitoids and different parasitoid release modes were investigated. Parasitoids were exposed to leaves infested with late second to early third instar Liriomyza sativae at two different host densities in Petri dishes. The total death rate of N. formosa released alone was density-dependent. And release modes also impacted the total death rate of parasitoids at a high host density. However, the oviposition number of D. isaea was significantly greater than that of N. formosa when they coexisted. In addition, host-feeding proportions were greatest among three host-killing behaviors: parasitism, host feeding and host stinging. These results contribute to a further understanding of parasitoids’ host-killing strategies. [ABSTRACT FROM AUTHOR]