The ecological study of how populations are regulated in their numbers and abundance has moved from single-factor investigations to more complex analyses of multiple factors. Plants and their insect herbivores present a favorable system for experimental manipulation in order to tease apart these multiply interacting factors. Dr. Harrison in a planning grant is studying the western tussock moth that feeds upon lupines across a 1000 km north-south transect. Competition for lupine herbage as well as predation by ants and other insect predators upon the moth larvae are being studied through experimental enclosures and other manipulations. Parasitism and insect dispersal are also being monitored in order to construct an abstract model of population regulation, with identification of differing control points along the north-south climatic gradient. %%% The complexity of ecological factors affecting the numbers and abundance of organisms makes experimental manipulations challenging but necessary. Dr. Harrison in a research planning grant is beginning an ambitious investigation of the western tussock moth that feeds on native lupines in coastal California, along with the ant and other insect predators of the moth, along a 1000 km north- south transect. One goal is to identify controlling factors in the population regulation of moths that are likely to differ in different parts of its latitudinal range.
