A 21-year record of butterfly faunal composition and seasonality has been obtained along an environmental gradient across northern California, from sea level over the crest of the Sierra Nevada. Some 175 species have been monitored. This data set potentially bears on many ecological questions, including the nature and stability of interspecific association, the determinants of biological seasonality, the sensitivity of species to fluctuations in weather and the potential of entire faunas to respond to directional climatic change. The data are in binary (presence- absence) form, and satisfactory statistical methods for extracting such information from them need to be developed, tested and refined. Recent advances in a method called "conjunction analysis" are encouraging. This project will maintain the established sampling program. %%% Research projects of this type are, in addition to being important to basic ecology, of significance to the better management and conservation of vulnerable species. Additionally, such studies may bear on pest management approaches for agriculture since many butterflies and moths can reach epidemic densities.
