User This is the Bible. If you're into tying your own flies; especially nymphs and other insects that spend most (but not all) of their lives under water, this is the book to reach for. It's not about tying. It's about what your efforts at tying try to replicate. And it's not limited in usefulness to California. These critters are more or less the same throughout the world. The book is over 50 years old. It will be equally current and valuable in the next millenium. Bugs are forever. Perhaps nomenclature will change. Classes come and classes go. But I have yet to meet a trout who spoke Latin. Sure, it's fun learning how to pronounce all the wonderfully descriptive names of each subject. However, it's much more important to know what each one looks like at various stages in its life. And it's critical to find out if they occur in your home waters. And if your local fishies like 'em. This is the book. It tells all.