Chrysophtharta bimaculata (Olivier) is a chrysomelid folivore of several Eucalyptus species, including E. (Monocalyptus) regnans, E. (M) delegatensis and E. (Symphyomyrtus) nitens. Both adults and larvae feed on the same tree species and eggs are laid directly onto host foliage. Adults feed and oviposit in aggregated swarms and, as a result, subsequent larval feeding may cause severe host tree defoliation and larval resource depletion. Further, previous research on a related chrysomelid has shown that factors associated with changing leaf age ( eg variation in toughness and nitrogen concentration) can seriously impact on larval survival.Because oviposition site selection is likely to be of fundamental importance to larval survival in C. bimaculata, the factors affecting oviposition site selection and the impact that the selected site had on subsequent larval establishment were chosen as the primary foci of this thesis.Research followed three main thrusts. In the first (Chapters 2-6), I documented exactly where C. bimaculata placed its eggs, both under natural and controlled conditions, from the individual leaf up to the level of tree species. Manipulative and correlative studies were used to determine what factors might affect site selection. C. bimaculata prefers to oviposit near the leaf tip and although there was no evidence that conspecific egg batches directly deter ovipositing beetles, leaves with egg batches on their tip are less preferred for oviposition. Other factors demonstrated to negatively influence oviposition site selection between leaves were increasing leaf toughness and conspecific beetle feeding damage. By altering leaf position it was demonstrated that leaf toughness, rather than leaf position, influenced C. bimaculata oviposition preference .. In chapter 5, I document the effects of egg batch placement on larval establishment. Wild, aggregated populations regularly deposit approximately one-third of egg batches on mature leaves unsuitable for neonate establishment. However, neonates had the ability to migrate to suitable leaves and establish with no increase in IV I would like to thank the following people and institutions for their contributions to my studies. Firstly, my supervisor Dr. Anthony Clarke for the great amount of time spent critically reviewing my experimental work and written material. His encouragement was very motivational and greatly appreciated. I would also like to thank my other supervisor Dr. John Madden for his suggestions, corrections and encouragement during my write up.I would like to thank the FFIC for the scholarship allowing me to conduct research into the interesting area of insect-plant interactions and the CRC for Sustainable Production Forestry for the use of office space and equipment, laboratory, glasshouse facilities and other equipment purchased for my research work. I would also like to thank Forestry Tasmania and ANM for providing information valuable to my work and for access to plantation and regeneration areas, North Forest Products for the use of clo...