Butterflies of the Pacific Northwest. Neill, William. (2007, Mountain Press Publishing Company).
This is a good introduction to the common Northwest species. This is a good book to start with and to carry in the field for those of us living in Oregon or Washington. An added bonus is that the author includes photos of the caterpillars of most species. Bill leads a couple field trips with Portland Audubon each year -- I highly recommend these for those living in the area.
The Butterflies of Cascadia. Pyle, R.M. (2002, Seattle Audubon Society).
The ultimate reference to all the butterflies of Oregon and Washington. Includes considerable information, including a description of subspecies, for each species. The book has some very useful comparison plates not found elsewhere and the range maps are much more detailed than you would find in guidebooks for the entire west or US. This is an essential reference for tough identification problems and regional variation, but it is not intended as a field guide. It is a bit sparse on photos and may be a bit detailed for the beginner, but this an essential reference and a good read.
Butterflies of Lane County. Makarushka, M. (2004, Eugene-Springfield NABA).
A nice little pocket guide oriented to Lane County but would be useful throughout the Willamette valley and elsewhere in the region. You can order it from the Eugene-Springfield NABA web site or get it from the Audubon House in Portland.
Butterflies of North America. Brock, J.P. & Kaufman, K. (2003, Houghton Mifflin Company).
A good guide to butterflies throughout North America and a convenient size to carry in the field. This is often the guide used during July 4th Census efforts. However, because the guide covers the entire continent, the beginner has to filter out those that occur in their area.
A Swift Guide to Butterflies of North America. Glassberg, J. (2012, Sunstreak Books).
This is a visual guide to the butterflies of North America. It provides large photos, down to subspecies of common species, but includes only a few cryptic annotations and no text. It serves as a good complement to other guides when you are trying to identify a new specimen want multiple sources.
Butterflies Through Binoculars: The West. Glassberg, J. (2001, Oxford University Press).
Good visual guide to western butterflies. This guide is very convenient to use in the field, especially for beginners. The photos are good, but small, and nicely arranged. Because the guide covers the whole west, though, you have to filter out the species that do not occur in your area and the range maps are not very detailed. Glassberg is more conservative about splitting species than Pyle so you will see some differences in scientifc names.
Butterflies of British Columbia. Guppy & Shepard. (2003).
Although focusing on British Columbia, this comprehensive hardbound book also covers Washington, northern Oregon and Idaho, and western Montana. The introductory section covers the natural history of butterflies. The remainder of the book provides considerable detail for each species found in the region. There are usually several photos of each species, including the many of the subspecies. Two unique features are the histograms showing the actual distribution of flight times and the use colored dots to indicate actual locations of subspecies sightings rather than the typical interpolated range maps.
Butterflies of America website.
Dr. Andy Warren, formerly at Oregon State, is the curator of this massive collection of 8,300 butterfly species. This website provides online images of adults, immatures, foodplants, and prepared specimens.
Butterflies and Moths of North America website.
This website, hosted by the USGS Northern Prairie Wildlife Research Center (NPWRC), provides another source of butterfly images. The hosts the site. You can select a state list that provides a menu for viewing photos, maps, and information about local species for the area of interest (but the maps map be dated).
North American Butterfly Association (NABA) checklist and English names of North American butterflies.
Cassey, Glassberg, Swengel, & Tudor (2001).
Describes the results of a NABA effort to standardize the common names for North American species. The list has both common and scientific names and includes notes about the committee's reasoning and supporting research. In general, they were purposefully conservative about recognizing new splits until more research can be published. Glassberg was a committee members, so as you might expect, his Butterflies through binoculars follows this scheme.
Standardized Common North American Butterfly Names (SC-NABN).
International Lepidoptera Survey.
Describes the results of an effort to standardize the common names for North American butterflies down to the subspecies level. List includes both common and scientific names.
Scientific names list for butterfly species of North America, north of Mexico.
Paul Opler & Andy Warren (2003).
Documents the authors most current thinking about scientific names for North American species with notes about the supporting research. List includes only scientific names. Note that Andy uses these names in maintaining the county records for Oregon.
An Atlas of Oregon Butterflies. Hinchliff, J. (1994, Oregon State University Bookstore).
A compilation of full page range maps by a team of experts. Useful for determining the range of subspecies (though obviously does not include county records added over the last 10 years). Unfortunately, this is out of print (as is a companion volume for Washington) though a handful of copies are still in circulation.
Butterflies of British Columbia. See the description above. The introductory chapter covers the general natural history of butterflies with some unique content I have not seen elsewhere (e.g., a study of bird predation for various species).
Butterflies of North America: A Natural History and Field Guide. Scott, J. (1986, Stanford University Press).
Despite the title I cannot imagine using this large volume as a field guide. The first section gives a detailed account of the biology and natural history of butterflies. The bound volume is more convenient for reading but the CD-ROM version provides easier access to some information.
Lepidoptera of the Pacific Northwest: Caterpillars and Adults. Miller, JC & Hammond, P.C.
(2003, USDA Forest Service).
A guide to selected butterfly and moth caterpillars of the Northwest. Check their website to see if copies are still available.
Caterpillars in the Field and Garden: A field guide to the butterfly caterpillars of North America.
Allen, T.J., Brock, J.P., & Glassberg, J. (2005, Oxford University Press).
This recent book has caterpillar photos for several hundred butterfly species. Includes range maps and information on host plants and where to find them. The style is similar to other books in the "Butterfly through Binoculars" series.
Lepidoptera of the Pacific Northwest: Caterpillars and Adults. Bjorkland, N.
(2004, Eugene-Springfield NABA).
A guide to places to find butterflies in Lane County, OR. Includes maps, directions, and recommended time of year. I understand he is working on a similar guide for the whole state.
100 Hikes of ... Sullivan, W.L.
This series describes many trails that also happen to be good butterfly habitat. Sullivan provides instructions on how to get there as well as the condition of the trail.
Wildflowers of the Columbia Gorge Jolley, R..
(1988, Oregon Historical Society Press).
Jolley suggests a number of field trips and the peak time to visit them. Also, if you want to target a particular species, check the description of its host plant to determine when and where it flowers.
Plants of the Pacific Northwest Pojar & Mackinnon.
(1994, Lone Pine).
Fairly comprehensive guide to wildflowers, shrubs, and other plants west of the Cascades. Organized by plant family.
Field Guide to Pacific States Wildflowers Niehaus, T.F., and Ripper, C.L.
(1976, Houghton Mifflin).
Covers common plants of the Northwest. Organized by color but includes a useful key to plant families.
Sagebrush Country: A Wildlflower Sanctuary. Taylor, R.J.
(1992, Mountain Press).
Descibes common plants of the Great Basin that may not be covered by other guides.