1. Natural Products Utilization Research Unit, Agricultural Research Service, U.S. Department of Agriculture, University, Mississippi 38677, Chemicals Affecting Insect Behavior Laboratory, Beltsville Agricultural Research Center, Agricultural Research Service, U.S. Department of Agriculture, Beltsville, Maryland 20705, and Southern Weed Science Research Unit, Agricultural Research Service, U.S. Department of Agriculture, Stoneville, Mississippi 38776