Puddling butterflies in Los Padres National Park, Monterey County, California. The center two are Pale Swallowtails (Papilio eurymedon) and the outer two are Western Swallowtails (Papilio rutulus). This behavior is seen in many butterfly species and is thought to be for the purpose of ingesting salts and amino acids. It is mostly performed by males, and the collected sodium and other materials are often transferred to the female with the spermatophore during mating.