1. Department of Entomology, National Museum Natural History, Smithsonian Institution, Washington, D.C. 20560, National Institute of Standards and Technology (NIST), 100 Bureau Drive, Stop 8541, Gaithersburg, Maryland 20899, Centre de Recherches sur les Macromolécules Végétales, CNRS-CERMAV, affiliated with the Joseph Fourier University of Grenoble, BP 53, 38041 Grenoble Cedex 9 France, and DuPont Central Research & Development Department, Experimental Station, P.O. Box 80302, Wilmington, Delaware 19880-0302