1. Institut National de la Recherche Scientifique, INRS-Institut Armand-Frappier, 531, Bd des prairies, Laval, Quebec, Canada H7V 1B7, Department of Zoology, University of Florida, Gainesville, Florida 32611-8525, and Institut Rosell-Lallemand Inc., 8480, boulevard Saint-Laurent, Montréal, Quebec, Canada H2P 2M5