Insect Population Ecology

Expressing propulation changes; density dependent processes affecting cultures of single species; composititions between species for a limited resouce; parasites and predatrs; climate and weather; life tables and their use in population chages of some forest insects; biological control.

Dr. Timothy Schowalter has succeeded in creating a unique, updated treatment of insect ecology. This revised and expanded text looks at how insects adapt to environmental conditions while maintaining the ability to substantially alter their environment. It covers a range of topics- from individual insects that respond to local changes in the environment and affect resource distribution, to entire insect communities that have the capacity to modify ecosystem conditions.Insect Ecology, Second Edition, synthesizes the latest research in the field and has been produced in full color throughout. It is ideal for students in both entomology and ecology-focused programs. NEW TO THIS EDITION:* New topics such as elemental defense by plants, chaotic models, molecular methods to measure disperson, food web relationships, and more* Expanded sections on plant defenses, insect learning, evolutionary tradeoffs, conservation biology and more* Includes more than 350 new references* More than 40 new full-color figures

Combining breadth of coverage with detail, this logical and cohesive introduction to insect ecology couples concepts with a broad range of examples and practical applications. It explores cutting-edge topics in the field, drawing on and highlighting the links between theory and the latest empirical studies. The sections are structured around a series of key topics, including behavioral ecology; species interactions; population ecology; food webs, communities and ecosystems; and broad patterns in nature. Chapters progress logically from the small scale to the large; from individual species through to species interactions, populations and communities. Application sections at the end of each chapter outline the practicality of ecological concepts and show how ecological information and concepts can be useful in agriculture, horticulture and forestry. Each chapter ends with a summary, providing a brief recap, followed by a set of questions and discussion topics designed to encourage independent and creative thinking.

Insects are far and away the largest group of animals on earth, with over a million described species, and they occupy a wide range of ecological niches - they may be herbivores, predators, parasites or decomposers. Some are of particular economic importance as pests of agriculture and forestry, as vectors of animal and human disease, or as species of interest to wildlife conservation, so an understanding of the processes determining their numbers is of considerable practical value.

Population and environment; Numerical change in insect populations; Current theories to explain insect numbers; The study of natural populations; The further development of research on insect populations.

The virtual impossibility of extracting the many different species from a habitat with equal efficiency by a single method (e.g. Nef, 1960). 1.1 Population estimates Population estimates can be classified into a number of different types; the most convenient classification is that adopted by Morris (1955), although he used the terms somewhat differently in a later paper (1960). 1.1.1 Absolute and related estimates The animal numbers may be expressed as a density per unit area of the ground of the habitat. Such estimates are given by nearest neighbour and related techniques (Chapter 2), marking and recapture (Chapter 3), by sampling a known fraction of the habitat (Chapter 4-6) and by removal sampling and random walk techniques (Chapter 7). Absolute population The number of animals per unit area (e.g. hectare, acre). It is almost impossible to construct a budget or to study mortality factors without the conversion of population estimates to absolute figures, for not only do insects often move from the plant to the soil at different developmental stages, but the amount of plant material is itself always changing. The importance of obtaining absolute estimates cannot be overemphasized.

Insects multiply. Destruction reigns. There is dismay, followed by outcry, and demands to Authority. Authority remembers its experts or appoints some: they ought to know. The experts advise a Cure. The Cure can be almost anything: holy water from Mecca, a Government Commis sion, a culture of bacteria, poison, prayers denunciatory or tactful, a new god, a trap, a Pied Piper. The Cures have only one thing in common: with a little patience they always work. They have never been known entirely to fail. Likewise they have never been known to prevent the next outbreak. For the cycle of abundance and scarcity has a rhythm of its own, and the Cures are applied just when the plague of insects is going to abate through its own loss of momentum. -Abridged, with insects in place of voles, from C. Elton, 1924, Voles, Mice and Lemmings, with permission of Oxford University Press This book is an enquiry into the "natural rhythms" of insect abundance in forested ecosystems and into the forces that give rise to these rhythms. Forests form unique environ ments for such studies because one can find them growing under relatively natural (pri meval) conditions as well as under the domination of human actions. Also, the slow growth and turnover rates of forested ecosystems enable us to investigate insect popula tion dynamics in a plant environment that remains relatively constant or changes only slowly, this in contrast to agricultural systems, where change is often drastic and frequent.

In this book I have tried to bring together the major developments in the study of insect populations in tropical environments. In some ways, this task has been a difficult one because conceptually it is virtually impossible to limit a discussion of insect ecology to the tropics, since the same concepts, theories, and hypoth eses concerning the mechanisms by which habitats support insect populations often apply both to temperate and to tropical regions. Thus one might argue effectively that a book such as Peter Price's Insect Ecology represents a more comprehensive treatment of insect ecology, including the tropical aspects. Yet because there has been a tremendous amount of new study on insects in the tropics in recent years, and because there has also been a strong historical interest in tropical insects, judging from early museum expeditions and medically and agriculturally oriented studies of insects in the New and Old World tropics, I believe there is a place for a book dealing almost exclusively with tropical insects. But logically so, such a book by necessity incorporates data and informa tion from Temperate Zone studies, if for no other reason than because insights into the properties of tropical environments often emerge from compariso'ns of species, communities, or faunas between temperate and tropical regions. An understanding of insect populations in the tropics cannot be divorced from a consideration of Temperate Zone populations.

The papers in this volume were presented at a symposium/workshop on "The Estimation and Analysis of Insect Populations" that was held at the University of Wyoming, Laramie, in January, 1988. The meeting was organized with financial support from the United States - New Zealand Cooperative Science Program and the University of Wyoming. The purpose was to bring together approximately equal numbers of quantitative biologists and biometricians in order to (1) provide a synthesis and evaluation of currently available methods for modeling and estimating parameters of insect population, and to (2) stimulate research into new methods where this is appropriate. The symposium/workshop attracted 46 participants. There were 35 papers presented in four subject areas: analysis of stage-frequency data, modeling of population dynamiCS, analysis of spatial data, and general sampling and estimation methods. New results were presented in all these areas. All except one of the papers is included in the present volume.