1. Department of Biological Sciences, University of Durham, South Road, Durham, U.K.,
2. Danish Bilharziasis Laboratory, Jægersborg Allé 1D, Charlottenlund, Denmark,
3. Faculty of Tropical Medicine, Department of Medical Entomology, Mahidol University, Bangkok, Thailand,
4. Shoklo Malaria Research Unit, Mae Sod, Thailand,
5. Centre for Tropical Medicine, Nuffield Department of Medicine, John Radcliffe Hospital, Headington, Oxford, U.K.