The addition of internal horizontal baffles to Malaise traps had no effect on numbers of Tabanidae collected or on species representation. The number of Tabanids collected in unbaited malaise traps with an opening that was 4 ft. high x 2 ft wide was statistically equivalent to the number collected in a standard 4 ft x 4 opening CO2 baited trap, but traps with an opening that was 2 ft high x 4 ft wide produced a mixed response depending on whether the top half or the bottom half of the standard opening was closed, the number of Tabanus subsimilis Bellardi collected in the standard CO2 baited trap. When the bottom half was closed, the number collected was usually significantly less than the number collected in the standard unbaited Malaise trap.