Until we began to use radar to study the flight of honey bee (Apis mellifera) drones observations of drone flight were non-recordable and based on observations made using a queen (or queen pheromone lure) tethered below a balloon. Zmarlicki and Morse, and Gary, were the first to publish studies in which a queen or the newly identified queen sex pheromone (9-oxodec-trans- 2-enoic acid) was used to attract drones flying in mid-air. They discovered that certain areas, usually beyond 60 m from an apiary, were 'hot spots' where many drones responded to the pheromone (6 to 30 m above ground) whereas in other seemingly similar areas either few or no drones would respond. They coined the term drone congregation area (DCA) for such a hot spot. Zmarlicki and Morse made the logical assumption that DCAs were mating areas, i.e. since the daily flights of drones from colonies begin before those of virgin queens, and since there are areas where drones congregate, then those areas must be where the virgin queens go and where mating occurs. In 1989, some 26 years after their discovery, 11 of the 12 DCAs located near Ithaca, New York, USA, in the 1960s were found to still have drone activity. Similar long-term observations of the remarkable locational constancy of DCAs were made by the Ruttners and their colleagues in Austria and Germany.