The development of the solitary endoparasitoid Meteorus gyrator was compared in the six larval stages of its host, the tomato moth Lacanobia oleracea, and at five constant temperatures. The host instar at the time of parasitism had a marked effect on the larval developmental period of the parasitoid, such that larvae derived from eggs oviposited in first instar hosts took approximately 18 days to egress, whilst those derived from eggs oviposited in sixth instar hosts took <10 days. The weight of cocoons was greatest when oviposition was into final instar hosts, where female cocoons averaged 12.8 mg, and lowest in those derived from eggs oviposited into first instars (9.2 mg). The parasitoid's larval development rate in third instar hosts increased with temperature increments in a linear fashion up to 25[degree]C, after which development times were only marginally increased. At 10[degree]C, the mean larval development time was approximately 90 days and pupal development 35-40 days, whilst at 25[degree]C development times were 10-11 days for larvae and 6-7 days for the pupae. In the majority of cases, overall development times were marginally longer (<1 day) in females than in males. Life cycle and development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Abiotic factors; Physical factors Lacanobia oleracea (Noctuidae); Development; Hymenopteran parasites; Meteorus gyrator; Parasite developmental duration, host stage of development & temperature effects; Temperature Meteorus gyrator (Braconidae); Development; Lepidopteran hosts; Lacanobia oleacea; Developmental duration, host stage of development & temperature effects; Temperature none