Tolerance to thiarubrines from Ambrosia chamissonis by the rare moth Lasionycta wyatti

The larvae of a rare noctuid moth, Lasionycta wyatti, were found to be asso ciated with the stems and roots of Ambrosia chamissonis, a species found al ong sandy beaches in western North America. High-performance liquid chromat ographic (HPLC) analyses of L. wyatii larvae and their frass revealed signi ficant amounts of thiarubrines, secondary compounds characteristic of this host plant. Artificial diet studies showed that thiarubrines were well tole rated by these larvae. These same diets, however, were toxic to larvae of M anduca sexta and inhibited larval growth of Spodoptera litura. Even in the presence of simulated sunlight, artificial diets containing thiarubrines di d not affect larvae of L. wyatti. However, dietary incorporation of thiophe nes, natural UV-activated breakdown products of thiarubrines, was deleterio us to larvae of L. wyatti.