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The solitary endoparasitoid,Microplitis rufiventris, attacks and can develop in earlier instars ofSpodoptera littoralislarvae with preference to third-instar larvae. We used the last stadium (sixth instar), a stage which is not naturally parasitized. The newly moulted larvae (0–3 h old) of this stadium were more acceptable for parasitization by the wasp females than the older ones (24 h old). Parasitization byM. rufiventriswasp of last instarS. littoralislarvae leads to dose (no. of eggs + parasitoid factors)-dependent effects which were more pronounced at 20°C than at 27°C. A single oviposition into a sixth instar host larva resulted in normal development of the host. However, superparasitization increased the proportions of developmentally arrested hosts and number of live wasp larvae. Development of supernumerary individuals of the parasitoid in the host larva leads to dose-related adverse effects on host growth and development. The present study may provide interesting opportunities for studying the physiological bases of host–parasitoid interactions and parasitoid intra-specific competition in the biological system considered. [ABSTRACT FROM AUTHOR]

The influence of sublethal dietary levels (0.4 p.p.m.) of a chitin synthesis inhibitor lefenuron {N-[2,5dichloro-4-(1,1,2,3,3,3,-hexafluoropropoxy)-phenylaminocarbonyl]-2 ,6-difluorobenzamide} on the development of Microplitis rufiventris teratocytes was investigated. Observations and data were taken on maturing teratocytes, i.e. at the end of parasitoid development. When embryogenesis of the parasitoid eggs was initiated in treated hosts, the dissociated cells of the embryonic membrane of some of the parasitoid larvae did not liberate in the haemolymph of the host, whereas in the other hosts, the released ones as individual cells scored the largest mean number per host larva. When young teratocytes were exposed to the treatment they were found in some cases clumping in masses or clustered around the parasitoid larvae. In treated hosts, different size classes of teratocytes co-existed. Larger and morphological abnormal cells were more common in hosts which contained older teratocytes at the time of treatments. Abnormal teratocytes were associated with developmental abnormalities of parasitoid larvae, possibly due to deterioration of the host environment. This observation was common in treated hosts and in few cases of untreated ones. A significant decrease in teratocyte size occurred 24 h after parasitoid emergence. Observations and results obtained in the present work suggested that: (1) teratocyte may function in controlling the growth and successful development of parasitoid larvae; (2) they might have a protective function through sequestering abnormal materials issuing in the haemolymph of the host either during the course of parasitoid development or due to external stress; and (3) number of teratocyte cells liberated from the embryonic membrane of parasitoid egg is not constant. [ABSTRACT FROM AUTHOR]

Presents information on a study which examined mature teratocytes in the body cavity of Spodoptera littoralis that was attacked by Microplitis rufiventris Kok. wasp. Methodology; Results and discussion.

Precocenes I & II (PI & PII) and juvenile hormone I (JHI) were topically tested on unparasitized and Microplitis rufiventris parasitized Spodoptera littoralis larvae. Parasitism interferes with normal host response to these compounds, decreasing their effectiveness. In all cases, the effect was dose-dependent. In contrast to PII or JHI, the lower dose of PI was more effective than the higher one. Application of JHI to S. littoralis larvae was less harmful to parasitoid development than either PI or PII. It is therefore emphasized that the commercial utilization of insect growth regulators should be undertaken carefully to minimize possible disruptive effects on developing parasitoids. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined the effects of superparasitism on the size and number of teratocytes found in the host Spodoptera littoralis at the completion of development of the solitary endoparasitoid Microplitis rufiventris. Major functions of teratocytes; Materials and methods; Results and discussion.

Provides information on a study which examined the effect of Precocene II, an anti-juvenile hormone, to the different development ages of Microplitis rufiventris Kok. teratocytes. Information on Microplitis rufiventris Kok; Materials and methods used in the study; Results and discussion.

1 IntroductionMicroplitis rufiventris Kok. (Hym., Braconidae) is an internal solitary parasitoid of many noctuid caterpillars including the cotton leafworm Spodoptera littoralis (Boisd.) (Kokujev 1914; Hammad et al. 1965; Gerling 1969), the lesser cotton worm S. exigua Hbn. (Meier 1929; Thompson 1946; El-Minshawy 1963); S. latebrosa Lederer (Hammad et al. 1965) and American bollworm Heliothis armigera Hbn. (Meier 1929; Ibrahim & Tawfik 1975). When the egg of M. rufiventris hatches in its host, S. littoralis, spherical cells from the serosa that envelope the parasitoid embryo are released into the host’s haemolymph. Approximately 400 cells are liberated from an egg of the parasitoid. These cells increase in size, reaching a maximum average diameter of 137 μm at the completion of parasitoid development (Khafagi 1997). These cells are most frequently called ‘teratocytes’ (— 1968, 1971; Vinson 1970). It is reported that the presence of large numbers of the teratocytes is indicative of superparasitism but their number does not give an indication to the exact number of parasitoid eggs from which the cells have been derived (—, — Khafagi et al. 1998). Therefore, it was of interest to initiate prediction studies on egg and teratocyte numbers in superparasitized host larvae. [ABSTRACT FROM AUTHOR]