A robust procedure for visual stabilisation of hovering flight position in guard bees of Trigona (Tetragonisca) angustula (Apidae, Meliponinae)

Summary

• 1. In the stingless bee, Trigona (Tetragonisca) angustula, hovering guard bees keep their position relative to a moving stripe pattern mounted on the front face of the nest box constant by flying forwards and backwards parallel to the pattern movement (Fig. 2).

• 2. The response is guided by two cues: (1) image position and motion of the pattern and (2) the retinal position of the nest entrance (Figs. 2–5).

• 3. Guard bees react to an expanding and contracting pattern by moving away from and towards the nest box (Figs. 6, 7). Bees always fly away from an expanding pattern in a direction that is defined by a line connecting the centre of expansion with the bee's position at the time the movement starts (Fig. 8).

• 4. A procedure based on Collett's 2nd optomotor rule can explain the ability of the bees to determine visually the direction of compensatory thrust (Fig. 10). The procedure is robust in 3 respects: (1) there will be no thrust generated in response to animal rotations as long as a scene contains contrast elements throughout the visual field; (2) errors in the direction of compensatory thrust are small even if the local direction of image motion alone is taken into account and not its magnitude; (3) only very few pattern elements are needed for the procedure to work.