Ideally, the tunnel-like trap should be placed where animals can pass through it several times a day. Flies are brushed off of the animals while they are in the device. The trap functions somewhat like a minnow trap. The flies move through the angled side slats to light and are trapped between the slats and the outer screened sides of the trap. It is easy to move into the collecting area but very difficult to get out.
Horn flies die naturally after a short time off of the animal.
Dead flies that accumulate in the trap can be removed but scavenger insects will do an effective cleanup job if the trap is not cleaned. Effectiveness Cattle passed freely through the trap, leaving behind many of the horn flies that were on them. While the trap caught some face flies, it did not result in any effective reduction in fly numbers per head. Very small numbers of stable flies and horse flies were caught in the traps but the traps do not provide effective control of these species. Placement As with dust bags and back rubbers, placement of fly traps is important.