none Artificial and modified natural hosts were exposed to females of the gypsy moth (Lymantria dispar (L.)) hyperparasite, Eurytoma appendigaster (Swederus), to investigate its host recognition behavior on the primary host, which are cocooned larvae of the gypsy moth parasite, Cotesia melanoscela (Ratzeburg). material(s) which caused drilling behavior by the hyperparasite on host cocoons were extracted with both polar and non-polar solvents. However, cocoons washed with large volumes of solvent still caused substantial drilling activities by females, suggesting that additional cues may be important. Results suggest that host recognition in this hyperparasite involves a variety of host characteristics.