Providing a particularly timely survey of invertebrate peptide hormones, this book closely examines the recent explosion of interest in this subject, and focuses on two important and related aspects. First, many of the peptides are neurohormones with chemical characteristics resembling, sometimes closely, established vertebrate neurohormonal peptides. In this way these findings have had considerable impact on our understanding of the origin and evolution of peptide regulators. Second, with the availability of techniques such as HPLC and cDNA probes that have allowed detailed study of vertebrate peptides, significant advances have been made recently in our understanding of the physiology and biochemistry of native invertebrate peptides. This volume provides a synthesis between these two aspects of current investigative activity.