This volume is the result of a symposium entitled "Variation in Life Histories: Genetics and Evolutionary Processes" sponsored by the Program in Evolutionary Ecology and Behavior of the University of Iowa and held in Iowa City on October 13 and 14, 1980. Prompted by a recent upsurge of interest in the evolution of life histories, we chose this topic because of the obvious association between life history traits and Darwinian fit ness. If such an association were to be fruitfully investigated, it would require the closer cooperation of population and evolutionary ecologists and quantitative and population geneticists. To encourage such an association, our symposium had four major aims: first, to facilitate intellectual exchange across disciplines among an array of biologists studying life histories; second, to encourage exploration of genetic variance and covari ance for life history traits; third, to consider the ecological background for genetic vari ability; and finally, to facilitate a comparative overview both within and among species. Obviously such broad aims cannot be met totally in a single volume, but we think we have succeeded reasonably well in providing a representative and nourishing intel lectual feast. We see this book as a stimulus to the coordination of future efforts in an important and expanding area of inquiry. We have divided the book into six sections."

This volume results from a symposium entitled "Species and Ufe History Patterns: Geographic and Habitat Variation," held during the National Meeting of the Entomo logical Society of America in Denver, Colorado, USA in November, 1979. The stimu lus to assemble papers on this theme emerged from continuing discussions with col leagues concerning controversies in ecology and evolutionary biology, namely those associated with plant-herbivore interactions, life history theory, and the equilibrium status of communities. The study organisms used in this series of reports are all either herbivorous insects or those intimately associated with plants. In this volume we stress the variation found in life history traits and address some of the problems inherent in current life history theory. We include as life history traits not only traditional variables such as fecundity, size of young, and age to first and peak reproduction, but also diapause and migration, traits that synchronize reproduction with favorable plant resources. Because life history traits of phytophagous insects are influenced in part by spatial and temporal variation in the quality and availability of their host plants, we also consider the role that dis continuities in plant quality play in reducing insect fitness. Lastly, much of the tra ditional life history theory concerns itself with differences between the evolution of traits or constellations of traits when populations incur primarily density-independent, compared to density-dependent, mortality. Consequently, we address this issue and attempt to shed light on the equilibrium status of several phytophagous insect com munities."

This volume is an outgrowth of a Symposium entitled "Evolution of Escape in Space and Time" held at the XV International Congress of Entomology in Washington, D. C., USA in August, 1976. The choice of topic was prompted by recent advances in evolutionary ecology and the apparent suitability of insect migration and dia pause as appropriate material for evolutionary studies. In the event, that choice seems amply justified as I hope a perusal of these papers will show. These Sympos ium papers hardly cover the topic of the evolution of escape mechanisms exhaustively, and I am sure everyone will have his favorite lacuna. Some of the more obvious ones are indicated by Professor Southwood in his Concluding Remarks at the end of the book. The purpose of the Symposium, however, was not complete coverage, but rather to indicate the potential inherent in insect migration and diapause for the study of evolutionary problems. In that I think we have succeeded reasonably well. These papers are expanded and in some cases somewhat altered versions of the papers delivered in Washington. This has allowed greater coverage of the topics in question. I suggested a format of a general overview of a topic emphasizing the author's own research con tributions. In general the papers follow this outline although emphases vary. Two of the authors, Dr. Rainey and Dr. Lumme, were unable to attend the Symposium. Dr. Rainey's paper was read by Mr. Frank Walsh, but Dr."

This volume results from a symposium entitled "Species and Ufe History Patterns: Geographic and Habitat Variation", held during the National Meeting of the Entomo- logical Society of America in Denver, Colorado, USA in November, 1979. The stimu- lus to assemble papers on this theme emerged from continuing discussions with col- leagues concerning controversies in ecology and evolutionary biology, namely those associated with plant-herbivore interactions, life history theory, and the equilibrium status of communities. The study organisms used in this series of reports are all either herbivorous insects or those intimately associated with plants. In this volume we stress the variation found in life history traits and address some of the problems inherent in current life history theory. We include as life history traits not only traditional variables such as fecundity, size of young, and age to first and peak reproduction, but also diapause and migration, traits that synchronize reproduction with favorable plant resources. Because life history traits of phytophagous insects are influenced in part by spatial and temporal variation in the quality and availability of their host plants, we also consider the role that dis- continuities in plant quality play in reducing insect fitness. Lastly, much of the tra- ditional life history theory concerns itself with differences between the evolution of traits or constellations of traits when populations incur primarily density-independent, compared to density-dependent, mortality. Consequently, we address this issue and attempt to shed light on the equilibrium status of several phytophagous insect com- munities.