The "Field Guide to Western Butterflies" by Paul A. Opler, published in 1999 by Houghton Mifflin Harcourt Publishing Company, is a part of the Peterson Field Guides series. This trade paperback book, with a length of 7.2 inches and a height of 1.1 inch, features illustrations by Amy Bartlett Wright and contains 560 pages filled with information about various butterflies found in the west. It is a comprehensive guide for nature enthusiasts looking to identify and learn more about these fascinating creatures.