Standing and hovering guards of the stingless bee Tetragonisca angustula complement each other in entrance guarding and intruder recognition.
Martin H. Kärcher and Francis L. W. Ratnieks
Previous research has shown that the colonies of the stingless bee Tetragonisca angustula have hovering guards that can detect allospecific intruder bees with volatile odours or different body colour. However, conspecific intruders were not detected. Here we show that T. angustula colony entrances are also defended by guards standing on the entrance tube. These standing guards made very few errors in recognition, accepting 100% of the nestmates and rejecting 92% of the conspecific non-nestmates presented to them at the nest entrance. In addition, 87% of the nestmates contaminated with odours from the stingless bee Scaptotrigona bipunctata were rejected. Standing guards also reacted to volatile odours from the stingless bees S. bipunctata and Melipona rufiventris by switching to hovering. However, the defence reaction, i.e. the increase in the number of hovering guards, was not comparable to the reaction previously reported to citral, the propaganda chemical used by the obligate robber bee Lestrimelitta limao when attacking other bee colonies.