I know papers by W. Edrich, Erlangen University (Germany) that focused his study in the relationship between the gravity and the artificial light in observation hives. One of these papers was published in Anim. Behav. around of 1970. In a next e-mail I will sent the exact references. Good luck. Walter Farina, University of Buenos Aires. Walter Farina, University of Buenos Aires. Insectos Sociales inssoc