Checkerspot butterflies have been used as an extraordinarily successful model system for more than four decades. This volume presents the first synthesis of the broad range of studies of that system as conducted in Ehrlich's research group in Stanford, in Hanski's research group in Helsinki and elsewhere. Ehrlich's long - term research project on Edith's checkerspot helped establish an intergrated disipline of population biology in the 1960s and ever since has contributed many fundamental insights into the ecological and evolutionary dynamics of populations. Hanski's and his associates' work an the Glanville fritillary for the past 14 years has been instrumental in establishing the field of metapopulation biology and showing how theoretical and empirical work can be effectively combined in the same project.