This archive contains the raw data from a series of experiments with Trissolcus basalis and Trissolcus oenone to better understand the chemical basis mediating differences in host-specificity between these parasitoids. First, we compared the searching behaviour of T. basalis and T. oenone in open arena arrestment bioassays contaminated with footprint compounds from Nezara viridula and Cuspicona simplex. Trissolcus basalis spent four times longer searching for N. viridula than C. simplex, while T. oenone spent four times longer searching for C. simplex than N. viridula. We then conducted competition experiments to assess factors important to determining the outcomes of extrinsic and intrinsic contests between these parasitoids when they are simultaneously exposed to C. simplex egg masses. Trissolcus oenone, was the superior competitor in extrinsic and intrinsic contests. Finally, we recorded the antennal responses of T. basalis to egg extracts of N. viridula to tentatively identify potential contact kairomones used by this parasitoid to recognise and accept hosts.