Eggs and larvae of the braconid parasite,Dacnusa dryas(Nixon), were encapsulated by third instars of the alfalfa blotch leafminer,Agromyza frontella(Rondani). Capsule formation was followed by death of the parasites and melanization and size reduction of the cadaver. The incidence of encapsulation of solitary parasites was consistently low, decreasing the effective rate of parasitism by an average of 10%. Supernumeraries were encapsulated without exceptions. The importance of encapsulation to the stability of the host-parasite association is discussed.