Lymantria dispar; EMERGENCE-; PARASITES-; Parasitism of pupae stung by Coccygomimus disparis (Hymenoptera), USA; HYMENOPTERAN-PARASITES; Coccygomimus disparis; Stinging behaviour & pupal fate; MORTALITY-; SURVIVAL-; Pupae stung by Coccygomimus disparis (Hymenoptera); FOREST-AND-WOODLAND; Forest; DELAWARE-; Kent, Hartly; Stinging behaviour of hymenopteran parasite & pupal fate, forest habitat Coccygomimus disparis; FEEDING-BEHAVIOUR; LEPIDOPTERAN-HOSTS; Lymantria dispar; Stinging behaviour & pupal fate; FOREST-AND-WOODLAND; Forest; DELAWARE-; Kent, Hartly; Stinging behaviour & lepidopteran pupal fate, forest habitat Observations on stinging behavior of Coccygomimus disparis (Viereck), an introduced pupal parasite of the gypsy moth, Lymantria dispar (L.), and its impact on host fate were made in a field study at 3 sites in a forested community near Hartly, DE. Incidence of ichneumonid parasitism and other mortality sources were compared in hosts known and not known to have been stung by C. disparis. Both parasitism and other mortality were higher in stung pupae. Survival of pupae, as evidenced by emergence of adult moths known to have been stung by C. disparis, was significantly lower than those not known to have been stung at 2 of the 3 study sites, and at all 3 sites when only female pupae were considered. The only site where no difference was noted had sustained heavy mortality (>80%), induced by other factors, especially Calosoma sycophanta (L.) and Brachymeria intermedia (Nees). Parasitization by ichneumonids and B. intermedia, as well as incidence of disease and desiccation, were higher in pupae of L. dispar experimentally stung by C. disparis than in those which were not. Attacks by C. disparis ranged from 10 s to approximately 17 min in duration, but averaged <4 min. Host feeding by C. disparis females did not affect survival in stung hosts but did prolong attack duration. Attack duration differed among sites. none