Spiders are among the most diverse groups of terrestrial invertebrates, yet they are among the least studied and understood. This first comprehensive guide to all 68 spider families in North America beautifully illustrates 469 of the most commonly encountered species. Group keys enable identification by web type and other observable details, and species descriptions include identification tips, typical habitat, geographic distribution, and behavioral notes. A concise illustrated introduction to spider biology and anatomy explains spider relationships. This book is a critical resource for curious naturalists who want to understand this ubiquitous and ecologically critical component of our biosphere.