250 butterfly species studied (IMAGE) University of Nevada, Reno Caption Butterfly decline was estimated using data from 72 locations with at least 10 years of data per location and more than 250 butterfly species, including this Adelpha bredowii, or California Sister. The total time span encompassed by the study is 42 years, from 1977 to 2018, and the average length of time series from individual sites was 21 years. Credit Chris Halsch, University of Nevada, Reno Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.