The value of foliage as a food for herbivorous insect larvae depends upon the nutritive value of the plant tissue and the food processing capabilities of the insect years it has become increasingly clear that the characteristics that are most important in determining nutritive value of foliage are nitrogen, water, and toxin content, and possible also acidity. Much less is known about the factors that determine an insect's capability to process ingested materials to counter the characteristics of foliage that are potentially harmful. In very few cases have convincing mechanistic explanations been provided to explain why one insect species can grow will on a particular plant while another grows very poorly. It is the purpose of this research to assess the importance of various foliage characteristics that prevent effective food utilization by lepidopteran larvae, to identify biochemical characteristics of the insects that allow them to overcome these barriers, and to assess the metabolic costs of these adaptations. If this project achieves its objectives, the results and conclusions will be useful in explaining the relative susceptibilities of different types of plant species (both crop plants and wild plants) to different insect species (both pest species and non-pest species). This work may also explain the ability of some insects to switch food plants or adapt to new hosts. Thus, this research may help to clarify some of the biochemical factors that have fostered the evolution of diversity among insects, and to explain why some insects become pests and others do not.
