Visually controlled station-keeping by hovering guard bees ofTrigona (Tetragonisca) angustula (Apidae, Meliponinae)

Summary

• 1. Guard bees of the stingless beeTrigona (Tetragonisca) angustula typically hover in very stable positions on both sides of and close to the nest entrance; for most of the time they face the flight corridor or the nest entrance (Fig. 2). Individual bees occupy a distinct airspace which they can leave for short excursions but return to afterwards (Fig. 3). When they change their position, they adjust their body-axis orientation to keep the nest entrance within their frontal visual field (Fig. 4). The accuracy of station-keeping decreases with the distance from the nest (Fig. 5).

• 2. Guard bees stay tightly coupled to the nest when the whole nestbox is oscillated through 20 cm forward and sideways with respect to the direction in which the nest entrance is pointing. They hold their position and distance relative to the nest entrance by flying forward, backward and sideways while keeping the angular orientation of their body long axis constant for most of the time (Figs. 6, 7). They temporarily lag behind the nest movement when they actively change their angular orientation or when the nest moves away from them. After the movement of the nest stops, bees which have lagged behind regain hovering stations close to the nest (Fig. 8).