Trapping Flies

The middle of Massachusetts is in a drought, and our pastures have turned brittle and brown. We’ve stopped grazing, and now have all three groups of ruminants off pasture. There isn’t really anything to eat, and we need to keep our grazers from doing long-term damage to the pasture plants. The beef herd, our flock of sheep, and our little dairy herd, are in three different locations around the farm, but all three locations share similar characteristics. These ‘yards’ have to have good shade so that every animal can stay out of the sun comfortably throughout the day. We need easy access with water so that we can ensure there is a constant supply for thirsty livestock on a hot day. Finally, we need a close and ample hay supply, since all of animals are now eating purchased hay in place of pasture grazing.

Another concern that these events have raised for me is flies. One of the great side benefits of rotational grazing is the fact that the moving animals get to leave many of the flies behind every time they change pastures. Although this does not eliminate flies on the animals, it does enough to keep the situation somewhat reasonable. However, now that these groups of animals are stationary, the flies have the potential to get out of control. Our animals experience regular face-flies as well as the wide variety of biting flies. We have purchased several different types of flytraps to address this issue, all with varying degrees of effectiveness. However, last week we built a large biting-fly trap that is really interesting.IMG_3245

After some internet research, I found the Horse-Pal Biting Fly Trap, as well as several similar products both commercially made and built at home. I asked students in the Livestock Track to do some thinking and planning of their own as well, and last Friday we set to work trying to build one of these things ourselves. Taking inspiration and design elements from several different ideas, we came up with a trap that, so far, has proved to be effective. It cost us less than $100, we built it in four hours, and it is trapping flies.

This design is based on the observation that flies always fly up when leaving an animal that they have landed on. They can certainly fly down, but only go up and away when leaving their host, or when trying to escape. This trap takes advantage of this trait by enticing them to land on an object that mimics a potential host, and trapping them from above and funneling them into a space they cannot get out of. As they continue their attempts to fly up and away, they are funneled further and further up, and finally into the container on top, where they are trapped to die.

The black ball hanging beneath the trap is a painted horse-ball (sold as a toy for bored horses) which we have painted black. It warms in the sun to attract flies which, looking for a live animal, are drawn to warm dark objects. Once the flies have landed on the ball, they realize it is not what they were looking for, and fly up to leave. The screen pyramid-shaped section funnels them up toward the peak, which finally emerges inside a large re-purposed water-jug. Once they are in the jug, again they won’t fly down to get out, and just head up and away to be trapped against the side and eventually die.

We found a lot of innovative and creative designs out there for trapping flies, but this seemed like something we could figure out and build. So far it has been effective, and the jug is filling with flies. Yum!


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