Hogue, Charles L. Insects of the Los Angeles Basin. Natural History Museum of Los Angeles County, 1993. The only book a non-professional will ever need in southern California! This book thoroughly documents common and less than common insects of the region, with discussions of the life history and other lore of each one. Profusely illustrated with color photos and line drawings, and with references to technical literature for nearly all entries. Includes some arachnids as well.
Levi, Herbert W. and Lorna R. Levi. Spiders & Their Kin (a Golden Guide) . Golden Press, 1968. Small but loaded with information about arachnids of all kinds. Amply illustrated.
Insects & Spiders of North America (Audubon Series).
Checklist of Butterflies of San Diego County
Checklist of the Spiders of San Diego County
Checklist of the Spiders of Baja California
California beetles - information and photos
Millipedes and centipedes - similarities, differences and photos
Quino Checkerspot Up Close for USFWS Quino Test
Butterfly Identification Test