Coccygomimus disparis(Viereck) attacked most of the 16 novel hosts species offered in laboratory trials and produced viable adults in 7 of these species. The manner of host presentation significantly affected host recognition and acceptance; immobilized or concealed pupae were attacked more readily than writhing or exposed pupae. In a choice experiment,C. disparisused concealed greater wax moth pupae primarily for oviposition. Exposed wax moth pupae offered simultaneously were used byC. disparismore often for host feeding. Parasite preference for and improved efficiency with cocooned, concealed, or immobilized hosts suggests that butterflies and other lepidopteran species with exposed pupae will be used infrequently for reproduction. In contrast, it is predicted that several endemic defoliator pests are likely to become new host species, shouldC. disparisbecome established in Minnesota. Implications for sampling gypsy moth,Lymantria dispar(L.), are discussed. Attacks on gypsy moth should differ with the orientation and degree of concealment of pupae. Parasitism plus host feeding could cause more mortality to host populations than is disclosed by rearing.