This all-new edition includes more than 590 species, illustrated in lifelike positions on beautiful new color plates. With descriptions of all the butterflies that occur west of the 100th meridian in the United States and Canada, this guide has accurate information on ranges, habitats, flight seasons, food plants, and more. Brand-new color range maps and more than 100 color photographs accompany the species descriptions. Paul Opler is the author of several books, including the Peterson Field Guide to Eastern Butterflies. He is a professor and senior research scientist at Colorado State University and a vice president of the North American Butterfly Association. Amy Bartlett Wright wrote and illustrated the Peterson First Guide to Caterpillars and illustrated the Peterson First Guide to Butterflies and Moths.