The biology of four allied species of the genusCotesiaCameron is reviewed. All these species were reared from larvae of pest insects mainly belonging to the families Lymantriidae, Noctuidae, Pieridae and Plutellidae. They are larval endoparasitoids and considered as important agents for biological control of pest insects infesting different vegetable crops in Vietnam, such as cabbage, kohlrabi, small colza, cauliflower, peanut, soybeans, and various other legumes. Of those four species,Cotesia clethrogynaeLong sp. n., is described as new and illustrated; the biology and distribution of the other three allied species are given, they are illustrated and compared, and a key to four species is provided.This paper resulted from the identification of a new species ofCotesiareared from limantrid larvae ofClethrogynae turbataButler and the necessity to compare related species. The host is an important pest infestant on soybean, different beans, peas and peanut in Vietnam.