1. Wilson, D. M., J. Exp. Biol. (in the press).
2. Ewer, D. W., Ann. Natal Mus., 12, 367 (1953).
3. Pringle, J. W. S., Insect Flight (The University Press, Cambridge, 1957).
4. Slifer, E. H., and Finlayson, L. H., Quart. J. Micro. Sci., 97, 617 (1956).
5. Finlayson, L. H., and Loewenstein, O., Proc. Roy. Soc., B, 148, 433 (1958).