Thesis (M. Appl. Sc.) -- Lincoln University, 2008. / Also available via the World Wide Web.

Microplitis croceipes (Hymenoptera: Braconidae) is an endoparasitoid and potential biological control agent of the tobacco budworm, Heliothis virescens (Lepidoptera: Noctuidae), an agricultural pest. The first objective of the following research was to amend current larval life history descriptions of M. croceipes. Larval head capsule width measurements were used to distinguish instar, and exuvium in abdominal cavities of post-egression hosts were indicative of a molt during parasitoid egression. Data revealed the larvae of M. croceipes pass through five instars, rather than three, as is indicated in the literature. The second objective was to investigate the suitability of potential artificial diets to be used in in vitro rearing of M. croceipes larvae. Three concentrations each of glucose, trehalose, and protein, as well as a combination diet (derived from initial diet trials) were tested. Growth, molting, and death were noted for each diet, and data indicated that diet had a significant effect for each performance measure (p = 0.0000, p < 0.0001, p < 0.0001, respectively). Data also indicated that trehalose and protein were more vital to larval parasitoid development (growth and molting) than was glucose, but no larvae were reared passed the second instar on an artificial diet. The final goals of the research were to evaluate the plausibility of rearing M. croceipes larvae to adulthood in vitro and to investigate post-egression host defensive behavior. Larvae were dissected from their hosts just prior to egression and placed in a cell culture plate in previously collected host hemolymph. Larvae were able to initiate pre-egression behavior in an in vitro environment, and a small percentage (6.67%) exhibited ecdysial splitting of the cuticle, however, no larvae were able to make the final molt in vitro. Post-egression hosts exhibited defensive behavior that may suggest they play a role in protecting pupating parasitoids. When the parasitoid exuvium was pulled from the egression wound in the host, hemolymph loss occurred and duration of the defensive behavior significantly decreased (p < 0.0001), indicating the exuvium acted to plug the egression wound, which prevented the host from bleeding to death and made it possible for the host to exhibit defensive behavior.

Microplitis croceipes is a solitary endoparasitic wasp that oviposits in the hemocoel of Heleothis virescens larvae. Upon parasitization, the host larvaes physiology is altered; resulting in a compromised immune system and a decrease in the production of some vital proteins resulting in a terminal post-wandering prepupal state. Teratocytes, cells derived from the extraembryonic serosa of the parasitic wasp, mimic symptoms of parasitization when injected into host larvae, independent of other factors like polydnavirus and venom. Some of the inhibition of protein synthesis can be attributed to proteins secreted by the teratocytes (teratocyte secretory proteins or TSP). A fraction of TSP between 330 kDa inhibits protein synthesis in vivo, in the in vitro fat body and testes assays, and in the rabbit reticulocyte lysate and wheat germ extract assays. This fraction, however, has no effect on nucleic acid synthesis. Its effect on protein synthesis is dose dependent and exposure time sensitive. A 13.9 kDa protein isolated from TSP and expressed in a baculovirus system seems primarily responsible for the inhibition. Although TSP14 production was low, it did bind to the cell surface, enter the cell, and inhibit protein synthesis as the 330 kDa factor did.

Microplitis croceipes, one of the nectar feeding parasitoid wasps, has been found to associatively learn chemical cues through feeding. The experiments on M. croceipes are performed and recorded by a Sony camcorder in the USDA-ARS Biological Control Laboratory in Tifton, GA, USA. The experimental videos have shown that M. croceipes can respond to Coffee odour in this study. Their detection capabilities and the behaviour of M. croceipes with different levels of coffee odours were studied. First, the data that are related to trained M. croceipes behaviour was extracted from the experimental videos and stored in a Microsoft Excel database. The extracted data represent the behaviour of M. croceipes trained to 0.02g and then exposed to 0.001g, 0.005g, 0.01g, 0.02g and 0.04g of coffee. Secondly, indices were developed to uniquely characterise the behaviour of trained M. croceipes under different coffee concentrations. Thirdly, a preliminary model and its parameters were developed to classify the response of trained wasps when exposed to these five different coffee odours. In summary, the success of this thesis demonstrates the usefulness of data analysis for interpreting experimental data, developing indices, as well as understanding the design principles of a simple model based on trained wasps.