Identification, Images, & Information
For Insects, Spiders & Their Kin
For the United States & Canada
Butterflies Through Binoculars: The East
By Jeffrey Glassberg
Oxford University Press, 1999
ISBN: 0-19-510668-7
Cite: 2460 with citation markup [cite:2460]
I grab this book first when I'm looking to identify a butterfly.

Florida has its own edition
which I find extremely useful here in Gainesville, FL. I see on Amazon there is also a regional edition for the West.