1. Mechanical Engineering, Stanford University, 416 Escondido Mall, Stanford, CA 94305, USA
2. Experimental Zoology Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
3. Physics Department, Eindhoven University of Technology, PO Box 516, 5600 MB Eindhoven, The Netherlands
4. Department of Zoology, University of British Columbia, 4200-6270 University Boulevard, Vancouver, British Columbia, Canada V6T1Z4