Aerial defense of the nest by workers of the stingless bee Trigona (Tetragonisca) angustula (Latreille) (Hymenoptera: Apidae)

Summary The stingless bee Trigona (Tetragonisca) angustula has a sophisticated defense strategy against flying insect predators at the entrance of its nest. Groups of worker bees hover on both sides in front of the nest entrance tube, facing a flight corridor leading to the nest. Intruders which enter this corridor are attacked by these bees from the side and from behind and are forced to the ground by biting bees clinging to their wings. T. angustula is subject to predation by Lestrimelitta limao, a cleptobiotic stingless bee which performs organized raids on other nests to rob food supplies, larval provisions and nest constructing material. The presence of citral, released by L. limao during the raids, leads to a rapid increase in the number of hovering guard bees in front of T. angustula nests. This recruitment in response to citral suggests that the defense behavior in T. angustula has evolved under the pressure of L. limao raids and that citral functions in T. angustula as an alarm kairomone.