1. L. Sundström, University of Lausanne, IZEA, Bâtiment de Biologie, CH-1015 Lausanne, Switzerland; University of Bern, Ethologische Station Hasli, CH-3032 Hinterkappelen, Switzerland; and University of Aarhus, Department of Genetics and Ecology, DK-8000 Aarhus C, Denmark.
2. M. Chapuisat, University of Lausanne, IZEA, Bâtiment de Biologie, CH-1015 Lausanne, Switzerland, and Museum of Zoology, Palais de Rumine, Case Postale 448, CH-1000 Lausanne 17, Switzerland.
3. L. Keller, University of Lausanne, IZEA, Bâtiment de Biologie, CH-1015 Lausanne, Switzerland, and University of Bern, Ethologische Station Hasli, CH-3032 Hinterkappelen, Switzerland.