A recent reference:
Zeil, J. & Wittmann, D. Visually controlled Station-Keeping by
Hovering Guard Bees of Trigona (Tetragonisca) Angustula (Apidae,
Meliponae). Journal of Comparative Physiology A 165:711-718. 1989.
Author Address: J. Zeil
Univ Tubingen, Lehrstuhl Biokybernet
Morgenstelle 28
D-7400 Tubingen 1 Fed Rep Ger