The Xerces Society
Although it's still under development, the Web site for The Xerces Society contains some intriguing essays, such as "Why conserve invertebrates, anyway?" and a discussion of trangenic crops in "The Threat posed by Bt." Though the site contains some specific information about butterfly gardening, much of it is devoted to conservation efforts and the philosophy of maintaining biological diversity.
Butterfly Gardening: Creating Summer Magic in Your Garden
This book consists of 14 chapters, each written by a different author, on a variety of topics relating to butterflies. Topics range from choosing plants for a butterfly garden, to an exploration of butterfly eyesight, to methods for enticing pollinators into the garden. The works were compiled by the Xerces Society, a nonprofit organization dedicated to the prevention of human-caused extinctions of rare invertebrate populations.
Butterfly Gardening: Creating Summer Magic in Your Garden, The Xerces Society and The Smithsonian Institution, Sierra Club Books, 1998.