From the Cascadia Prairie-Oak Partnership a beautiful and useful guide to butterflies. Ann Potter and Rod Gilbert have put together a butterfly guide that is specific for South Puget Sound. It includes everything that you might see either in the prairies or elsewhere around the Sound, including some very uncommon species.
The guide includes local flight periods, habitat preference, larval host plants, and a few notes with key identifiable features and/or information. Flight periods are specific to SPS but species ID and ecology are transferrable to the South Coast. Several species are quite rare here in BC (Edith's Checkerspot, Dun skipper, Propertius Duskywing, Monarch). If you see these butterflies in BC please contact the provincial invertebrate specialist Jennifer Heron or Wild Research and make sure to document your sighting to the BC Conservation Data Centre.