The problem of how population sizes are determined by regulatory mechanisms and/or various independent environmental factors has long provided a controversial and challenging issue in theoretical and applied population ecology. From a practical point of view the subject is increasingly involved in the understanding of environmental issues such as conservation of biodiversity and means of biological control. This work seeks to explain and provide an historical background to the controversies surrounding the various theoretical and mathematical standpoints on the regulation of animal numbers. The authors challenge the mechanistic approach which underpins many accepted 19th-century "top down" paradigms of population regulation and present the case for a less rigorously deterministic ecology and an approach to population regulation and stabilization which emphasizes life history characteristics, physiological and behavioural processes of animals. The authors are respected workers in the field and have combined their research experience to produce a stimulating volume of interest to advanced researchers in ecology, population biology and evolutionary biology. This book should be of interest to popultion ecologists, conservation biologists, entomologists.