A new pyrrolizidine alkaloid, 14-deoxyparsonsianidine N-oxide, was isolated from adults of a danaine butterfly, Idea leuconoe. The compound appears to have been incorporated directly from the host plant, Parsonsia laevigata, together with other major analogs, during the larval stage. © 1994, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.