The study of the attack and displacement activities in the search for blood repast of several tabanid species is being carried out. The experiments were conducted in open areas located in the Research Campus of the Goeldi Museum, Belém, PA, and in the farm Morelândia, municipality of Santa Barbara, PA, from February 1998 to June 1999. The present work aims to study the potential of these insects in the transmission of diseases related to their ability to move among their hosts. Three horses were used as bait, 10, 30, 50, 70 and 110m away from two defined release points, (S1 and S2). The tabanids were marked with non-toxic ink and then released at the determined points. The data were recorded in spreadsheets, recording the species, release point, and horse where it was recaptured. A total of 1,999 tabanids were marked and released at point S1 and 1,278 at S2, and 564 (28.3%) and 180 (14.1%) were recaptured, respectively. The most abundant species collected, followed by the number of individuals and percentage of recapture are presented below: (S 1): T. occidentalis 315 (55.8%), T. sorbillans 65 (11.8%), D. bifascies 34 (6.0%), L. exaestuans 30 (5.4%), T. trivittatus 25 (4.5%), T. olivaceiventris 23 (4.0%) and others 70 (12.5%); (S2): T. occidentalis 167 (92.7%), T. trivittatus 7 (3.9%) and T. sorbillans 6 (3.4%). The recapture results show us that the species with the greatest importance in insisting on repasting were: T. discus (50%), T. occidentalis (38.6%), L. exaestuans (35.7%), T. importunus (29.1%), C. unicolor (25.0%), T. antarcticus (24.3%), T. glaucus (22.7%), T. olivaceiventris (22.3%) and T. discifer (21.0%). The species with the highest displacement capacity were: T.occidentalis (19.2% at 10m, 8.2% at 30m, 11.1% at 50m, 10.6% at 70m, 47% at 90m and 2.0% at 110m), T. trivittatus (6.3% at 10m, 3.6% at 30m, 1.3% at 50m, 2.0% at 70m, 0.4% at 90m and 0.4% at 110m) and T. sorbillans (12.1% at 10m, 3.3% at 30m, 4.3% at 50m, 8.3% at 70m). These results present new and useful information for livestock management, suggesting that a 200m distance between herds is sufficient as a barrier to prevent attacks of tabanids among their hosts
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