Basics: 2004, softcover, 372 pages, 300 species, 421 color photos, no range maps
Here is a great book on an area rich in butterfly species and uniqueness. Over 400 color photographs display 300 species of butterflies from the southern border of Texas. All butterflies of the area - common, vagrant, and accidental - are covered in this guide.
There is one species per page and most are illustrated with 2-3 photos. The more distinctive or rarer butterflies often have only one photo. All the photos are in color and do a good job of showing the field marks. My only minor critique about the photos is many appear to be overexposed or slightly hazy. This causes the colors to lack crispness.
It appears the photos are meant to mimic what you would encounter in the field. By this, I mean nearly all the hairstreaks, sulphurs, and satyrs are shown only with their wings closed (no dorsal views) while the duskywings, cloudywings, and flashers are shown only with their wings open (no ventral views), just as you would typically see in the field without collecting the butterfly.
The text starts with a paragraph on the description of the butterfly. This information is written well with very useful details. Another shorter paragraph offers comparisons to similar species. The "When and Where" paragraph gives general information on seasonal or monthly presence along with notes on the habitats in which the species is likely to be found.
I like the inclusion of "LRGV speciality" written at the beginning of the species account for the appropriate butterflies. Standing for "Lower Rio Grand Valley" and found on nearly half the species, it immediately informs the reader about the geographic uniqueness of the specimen for the US.
This is a great book to have when visiting far-south Texas and should help you identify nearly everything you encounter.
I've listed several related books below...
1) Butterflies: Northeastern Mexico by Garwood/Lehman
2) Butterflies of Arizona: A Photographic Guideby Stewart et al.
3) Butterflies of North America by Brock/Kaufman
4) The Butterflies of North America by Scott
5) Butterflies through Binoculars: The West by Glassberg
6) National Audubon Society Field Guide to North American Butterflies