The developmental stages of a solitary parasitoid, Lysiphlebus japonicus Ashmead, of the black bean aphid, Aphis craccivora Koch, were described by using light and scanning electron microscopy. Lysiphlebus japonicus has four larval instars. The first instar is mandibulate, caudate and has sclerotized spines. Supernumerary neonates are eliminated by powerful mandibles of the first hatched larva. The second instar has degenerative mandibles and is covered with small sclerotized bristles on abdominal segments; the cauda is short and blunt. The third instar is mandibulate; its cuticle is smooth and the caudal segment retrogresses to a short salient. The fourth instar is strong and hymenopteriform; their mandibles are smaller than those of the third instar, and various sensory organs are well developed, especially for the mouthpart. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Lysiphlebus japonicus (Aphidiidae); Development; Hemipteran hosts; Aphis craccivora; Developmental stages Aphis craccivora (Aphidoidea); Hymenopteran parasites; Lysiphlebus japonicus; Parasite developmental stages none