Ask some of their victims how to kill a Greenhead and you are liable to get an answer akin to swat it with a swatter, then a sledgehammer, then pull their wings and head off and drive a tiny stake through their heart. Greenhead flies are a large species of horsefly known for their painful bites and hunting for blood meals in large numbers. They are common in the Northeast marshes. The only real way to kill Greenhead flies is to trap them before they develop fully enough to move away from the marshes where they were born.

Construct a box made from the plywood pieces. The top and bottom are both open at this point so you will only need the four sides. Glue the sides of the plywood pieces at the corners in the shape of a box. Let the glue dry before attempting to nail the box together.

Hammer three nails into each side of the plywood edges. Inspect the sides to make sure that there are no gaps between pieces that would allow a greenhead to escape. If there are any gaps, seal them up with epoxy glue and let it dry overnight.

Align the top of the furrowing strips with the top corners of the box. Secure one strip at each outside corner of the box using nails or small screws.

Paint the legs and the box a glossy black. This will let the box absorb heat and contrast with the environment to get the attention of the greenhead flies.

Measure and cut a piece of metal insect screen to fit over the top of the box trap. Set it over the top to make sure you have cut it the right size. Remove the screen and measure 3 inches from the left and right sides.

Cut a 2.5-inch round hole in the screen in both locations 3 inches from the sides. Take the circular screen pieces that you cut out and cut a one-half-inch hole in the center of these pieces.

Fold each of these pieces into a cone shape. Cement the sides to retain the cone shape and let the glue dry overnight. Another option is to use screen wire to sew the cones into shape if you don't want to wait for glue to dry. Use some remaining screen that is not part of the top of the box to make two more cones of the same size.

Secure the metal insect screen to the top of the box trap with epoxy cement or small nails. Invert the cones over the top of the holes you cut in the screen and sew or glue them in place, narrow side up.

Invert a clear plastic container over each of the cones. These containers can be small cake boxes or other similar container. They should be large enough that a large number of greenheads can be collected without having to empty the trap every day. If the plastic containers you choose do not have a natural opening for the Greenheads to fly into, cut a 2.5-inch hole and glue one of the other cones into the hole. Glue it in place and repeat for the other container.

Secure the containers to the metal screen so that they do not move. Stretch a single piece of duct tape over the top of the box to hold each container in place.

Set the trap close to the area where greenheads breed. This would be in marshes, or swampy areas. Drive two stakes into the ground beside two legs of the trap to keep it stable. You can use zip ties to secure the legs to the stakes.

Hang the black beach ball on a string in the space underneath the box trap. The movement of the ball in the wind will attract the greenheads to the trap. With the heat, a greenhead will only survive 24 hours once trapped. Clean out the containers when it appears they are full.