Queen Harems of Higher Termites are Regulated by Queen Pheromone

Colonies of higher termites (Termitidae) are usually headed by one king and one queen. Striking exceptions have recently been described in several species, whose founding queens prematurely die and are replaced by harems of up to hundreds of neotenic queens, arising from unfertilized eggs. This complex breeding system calls for the presence of a mechanism which would control the onset of the harem and its size. Here we show in one of such species, Embiratermes neotenicus, that the sesquiterpenoid (3R,6E)-nerolidol, emitted by queens and eggs, delays the development of new neotenic queens. We prove its effect as an airborne signal and demonstrate its olfactory detection. We conclude that (3R,6E)-nerolidol acts as a queen pheromone which may ensure the correct timing of the founding queen’s replacement and optimize the harem size according to colony population and fitness of reigning queen(s), being thus the key regulatory element of the harem breeding system.