Soldiers in a stingless bee: work rate and task repertoire suggest they are an elite force

The differentiation of workers into different morphological sub-castes (e.g. soldiers) represents an important evolutionary transition and is thought to improve division of labor in social insects. Soldiers occur in many ant and termite species where they make up a small proportion of the workforce. A common assumption of worker caste evolution is that soldiers are behavioral specialists. Here, we report the first test of the “rare specialist” hypothesis in a eusocial bee. Colonies of the stingless bee Tetragonisca angustula are defended by a small group of morphologically differentiated soldiers. Contrary to the “rare-specialist” hypothesis, we found that soldiers worked more (+34-41%) and performed a greater variety of tasks (+23-34%) than other workers, particularly early in life. Our results suggest a “rare elite” function of soldiers in T. angustula, i.e. they perform a disproportionately large amount of the work. Division of labor was based on a combination of temporal and physica...