Pholetesor ornigis(Weed) is capable of parasitizing tissue-feeding larvae (fourth and fifth instars) as well as sap-feeding larvae (first, second, and third instars) ofPhyllonorycter blancardella(F). In no-choice tests, similar numbers of offspring were produced on first-fourth instars hut fewer on fifth instars. In choice testsP. ornigisproduced similar numbers of offspring on first, second, and third instars, but fewer on fourth instars and none on fifth instars. In the field primarily sap-feeding larvae were available during the first threeP. ornigisflight periods. However, tissue feeders were predominant during the partial fourth-generation flight period.