The comparative biology of the solitary endoparasitoid Meteorus gyrator (Thun.) was investigated in five noctuid pest species. Meteorus gyrator parasitized all larval stages of the noctuid pests Lacanobia oleracea, Mamestra brassicae, Spodoptera exigua, Spodoptera littoralis and Chrysodeixis chalcites. When female parasitoids were offered host larvae of all developmental stages, host larvae in their third stadium were parasitized most frequently in all species. When the parasitoid was offered a choice of third stadium larvae from each of the five lepidopteran host species, L. oleracea was the most frequently parasitized, followed by M. brassicae. The growth of L. oleracea and M. brassicae was markedly reduced when larvae were parasitized by M. gyrator, with the effect of parasitism on the remaining species being much less pronounced. In excess of 94% of parasitized hosts gave rise to live wasps in L. oleracea, whilst in M. brassicae only 52% of parasitized hosts gave rise to a live wasp, the remainder dying (44.6%) or pupating (3.1%). The larval development of the parasitoid was also strongly influenced by the host species. Thus, the development (egg to cocoon) of female wasps was most rapid in C. chalcites (9.7 [plus or minus] 0.09 days), and longest in M. brassicae (17.2 [plus or minus] 1.08 days). The cocoon weight of wasps, was also significantly affected by host species, with the heaviest female cocoons being derived from C. chalcites (10.4 [plus or minus] 0.16 mg) and the lightest female cocoons being derived from All. brassicae (7.0 [plus or minus] 0.14 mg). In all cases, the development times and cocoon weights of male parasitoids were less than those of female wasps. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts Noctuidae; Hymenopteran parasites; Meteorus gyrator; Parasite biology on different host species Meteorus gyrator (Braconidae); Life cycle and development; Lepidopteran hosts; Noctuidae; Parasite biology on different host species none