It has been suggested (Wright, 1958) that attractants or repellents for insects which normally fly to their destination should be tested against insects that are in flight during the tests. Moreover, the conditions of the flight should be as nearly natural as possible. This requires that the observation chamber should be large (to minimize wall effects), the illumination should be controllable, and the air movement and the odorous or other signals should be presented in a natural way. Finally, the movements of the insects should be recorded in three dimensions, and in as much detail as possible.