No doubt many of your readers are aware that, in 1863, Sir John Lubbock gave an account of an extraordinary hymenopterous insect which he had observed swimming in a basin of water taken from a pond at Chislehurst. Another observer (Mr. Duchess, of Stepney) had also found a single specimen about the same time; then, in 1881, Mr. Bostock found one in some pond water at Stone, Staffordshire, since which time it does not appear to have been recorded by any one. I have searched many ponds for it year after year, but without success.