A wide earthen pan is filled with fresh sand which has been passed through a sieve.

With the aid of a stick the thickness of a finger I make six vertical holes in the sand: they are conveniently far apart, and are eight inches in depth.

A _Hydnocystis_ is placed at the bottom of each; a fine straw is then inserted, to show me the precise position later.

Finally the six holes are filled with sand which is beaten down so that all is firm.

When the surface is perfectly level, and everywhere the same, except for the six straws, which mean nothing to the insect, I release my beetles, covering them with a wire-gauze cover.