Dissections of larvae from a routine collection of European pine shoot moth (Rhyacionia buoliana (Schiffermüller)) made on 12 October 1965 in a small red pine plantation in Con. VII, Mills Twp., Manitoulin Island, Ont., revealed the presence of larvae of an unrecognized parasite in approximately 44% of the 103 living shoot moth larvae obtained. This compares favourably with rates of approximately 40% found by the author for Orgilus obscurator Nees, the most effective internal parasite of shoot moth in southern Ontario. No adults of the unrecognized parasite were obtained at that time, and because of severe winter kill of the shoot moth, none were obtained in a sample made in the following spring from the same plantation. However, shoot moth larvae obtained in a sample taken on 4 October 1966 yielded similar larvae on dissection, and rearings produced adult parasites which were identified by Dr. W. R. M. Mason, Entomology Research Institute, Canada Department of Agriculture, Ottawa, Ont., as Agathis binominata Muesebeck. According to Muesebeck et al. (1951), Krombein et al. (1967), and Yates (1967), the following species are hosts of this parasite: Coleophora laricella (Hübner), Epiblema desertana (Zeller) , Epinotia nanana (Treitschke) , Petrova comstockiana (Fernald), Phalonia rutilana (Hübner) , Pulicalvaria coniferella (Kearfott) , P. piceaella (Kearfott) , and Rhyacionia frustrana (Comstock). Its association with Rhyacionia buoliana apparently has not been recorded previously.