Albert O. Bush is Professor and Chair of the Zoology Department, Brandon University, Brandon, Manitoba, Canada; he is a member on the editorial boards of several parasitology journals, is past-President of the Parasitology Section of the Canadian Society of Zoologists, and is an internationally known and respected ecological parasitologist. Jacqueline C. Fernàndez is a Research Associate in the Department of Biology, Wake Forest University, Winston-Salem, North Carolina, USA; she is a recognized expert on digenean-snail interactions and parasite biogeography. Gerald W. Esch is Editor of the journal of Parasitology and recipient of the 1999 Mentor Award from the American Society of Parasitologists; he is presently Charles M. Allen Professor of Biology at Wake Forest University. J. Richard Seed is a Ward Medallist and past-President of the American Society of Parasitologists; he is currently Professor of Parasitology in the Department of Epidemiology, School of Public Health, University of North Carolina at Chapel Hill, North Carolina, USA.