DISPERSAL, DENSITY AND HABITAT PREFERENCE OF THE BLOW-FLIES

phosphate and released in the northern Kruger National Park, South Africa. After a 1-weekilispersal period 69 baited blow-fly traps were placed in different habitat!}'pes and at varying distances around the release point. C. a/biceps were subsequently found to have covered up to 37,5 km ~ alld c: marginaliso3,5 km, suggesting dispersal rates per day of 2,20 km and 2,35 km for the 2 species, respectively. Calculation of density using the Lincoln Index yielded estimates per hectare of 7,56 C. a/biceps and 29,03 C. margina/is. Both species were trapped more numerously in forested environments than in open scrub, and both avoided arid scrubland. iNTRODUCTION Blow-flies have been considered important in the maintenance and spread of anthrax (Bacillus anthracis) during periodic epizootics in the northern Kruger Natio-nal Park (K.N.P.) (Pienaar, 1961; Braack, 1984). Flies arrive soon after the death of an animal to feed on blood at haemorrhaging body cavities, and deposit large num-bers of infective discard droplets on vegetation in the area, thus greatly increasing the probability of herbivo-rous mammals ingesting the pathogen in fatal doses (Braack, 1984). Chrysomyia a/biceps and C. marginalis are by far the most abundant blow-flies in the northern K.N.P. and are widespread throughout southern Afric