none The developmental times of both species were reduced under short-day photoperiod conditions. Photoperiod as well as parasitism markedly affected the number of moults of the host larvae and the developmental time of the parasite was correlated with its sex, the host's age and photoperiod. The haemolymph juvenile hormone titres of parasitized larvae were significantly higher than those of unparasitized larvae. The high levels of juvenile hormone were recorded prior and subsequent to parasite emergence. Importantly, parasitism interferes with the normal development of the host larvae. Biometrics; Circulatory system; Endocrinology; Reproduction; Life cycle and development; Life cycle; Developmental stages; Development; Parasites diseases and disorders; Parasites; Insect parasites; Hosts; Insect hosts; Host parasite relationships; Abiotic factors; Physical factors; Light Spodoptera littoralis (Noctuidae); Age, effect on developmental interactions with hymenopteran parasite; Haemolymph; Hormones; JH levels, larval haemolymph, effect of hymenopteran parasite; Larva, photoperiod relations; Ecdysis; Number of moults, relations with hymenopteran parasite; Hymenopteran parasites; Microplitis rufiventris; Parasitism effect on haemolymph JH levels; Host parasite developmental interactions, effect of photoperiod; Host parasite relationships; Developmental synchrony with hymenopteran parasite, photoperiod effects; Reaction of host to parasite; Larval JH titre response to Microplitis rufiventris (Hymenoptera); Photoperiod; Developmental interactions with hymenopteran parasite, relationship, larvae Microplitis rufiventris (Braconidae); Sexual dimorphism; Larval developmental time in lepidopteran host; Larva; Developmental interactions with lepidopteran host, photoperiod relations; Lepidopteran hosts; Spodoptera littoralis; Parasitism effect on host larval JH levels; Host parasite developmental interactions, effect of photoperiod; Host parasite relationships; Developmental synchrony with lepidopteran host, photoperiod effects; Reaction of host to parasite; Spodoptera littoralis (Lepidoptera) larval JH titre responses; Photoperiod; Larval developmental interactions with lepidopteran host, relationship