1. Department of Biology, University of California, Santa Cruz, California 95064, USA
2. Present address: Department of Wildlife Ecology, University of Wisconsin, Madison, Wisconsin 53706, USA
3. P.O. Box 73842, Davis, California 95617, USA
4. Department of Biology, University of California, San Diego, California 92093-0116, USA
5. John Muir Institute of the Environment, University of California, Davis, California 95616, USA
6. Department of Entomology, University of California, Davis, California 95616, USA
7. Department of Wildlife, Fish, and Conservation Biology, University of California, Davis, California 95616, USA