1. W. Hangartner andP. Masner, Experientia, in press (1973).
2. Stauffer compound No. R-20458.
3. All compounds were kindly provided by F. Hoffmann-La Roche, Ltd. Basel.
4. Results presented to members of the A.R.C. Unit of Invertebrate Chemistry and Physiology at Brighton (Prof.A. W. Johnson, Director) and Cambridge (Dr.J. E. Treherne, Deputy Director) on March 19 and 20, 1973.
5. W.E. Robbins, J.N. Kaplanis, M.J. Thompson, T.J. Shortino, C.F. Cohen andS.C. Joyner, Science161, 1158 (1968).