We assessed the adaptiveness of refraining from infanticidal probing at the third attack under triple parasitism in the parasitoid Echthrodelphaxfairchildii Perkins, by comparing fitness retus from the third attack with and without probing. Fitness retus were assessed in terms of the survival rate, mean developmental time, and mean adult head width of the progenies. Not probing was maladaptive under triple parasitism with oviposition intervals of 1/24 and 24/24 hours (where the numbers before and after the slash refer to the first-to-second and second-to-third oviposition intervals, respectively), although no significant difference was detected in fitness retus for oviposition intervals of 24/1 hours. We suggest that the cost of probing (especially the decrease in the chance of future ovipositions) is a reason for the seemingly maladaptive absence of probing.