Green Head Trap
Friday, August 11, 2006
“Life is like a box of chocolates”
Living out on the marsh at the mouth of the bay has it’s drawbacks.  Every summer the green heads attack.  I decided to do something about it and below I have included the Rutgers Plan for a green-head trap as well as the modifications and observations I have noticed in our trap.
Rutgers Design:  (My Changes below)
Building the Box Trap: The basic box trap design is shown above and at the bottom of the page.
Essentially the trap is a four-sided box having a screen top and open bottom. This box stands on legs so that its bottom is about 2 feet above the marsh surface. Flies enter the trap from below and move into secondary traps on the top of the box. The design is simple. The sides of the box can be made of a number of materials including plywood, cardboard, or plastic sheeting tacked to wooden framing. The trap dimensions have been developed experimentally and we urge the wise builder to pay strict attention to the following points:
1. Build a box 15 x 32 inches on a side fastened to corner posts. We use 1/4 plywood and 1 x 2 inch furring strips, but other materials can be used. Also nail a strip to the top of each side for later attachment of the screen top. The bottom of the box remains open. The optimal size for each side of the box is about 16 x 32 inches. In our tests, larger and smaller box traps were less efficient. Furthermore, these dimensions allow nine sides to be cut from a standard 4 x 8 foot panel. This means that the sides for nine traps can be cut from four 4 x 8 sheets of material.
2. We use separate legs 40 inches long which are attached to the trap when it is placed for catching flies. The box is fastened so that its lower leg is 24 inches above the ground surfaces. This is important because the greenhead fly usually flies at about this altitude.
3. The trap should be painted a glossy black to contrast with its surroundings and to absorb heat from the sun. Either shiny or dull black plastic sheeting attached securely to a frame is also satisfactory.
4. The top of the trap should be made of a metal insect screen. Plastic screening or sheeting will be damaged readily by birds seeking to get at the trapped flies and should not be used.
5. Take care in building the box and attaching the screen. Be sure there are no holes for escape of trapped flies. Once inside the box, most flies move to the top of the trap, through the screen cones and into collectors, described in Step 8.
6. Cut two holes in the screen roof of the box at diagonal corners. These holes should be 2 to 3 inches from the sides of the trap and 2 ½ inches in diameter. Make a cone of insect screen with a base of 2 ½ inches in diameter and 2 to 2 ½ inches high and with a hole ½ inch in diameter at the top.. After the piece of screen is cut, roll it into a cone and securely cement, staple or sew it with wire.
7. Cement the cones around the holes in the screen roof, using an all purpose or epoxy cement.
8. The two collectors can be any type of clear plastic container such as a shoe box or cake box. We have found that plastic bags are unsatisfactory because crows and other birds tear them open to feed on the trapped flies. We use round containers 10 inches in diameter and 3 to 4 inches high but square or rectangular boxes of similar size can also be used. Smaller collectors may require frequent emptying of flies and, therefore, are inconvenient.
9. Cut a 2 ½ inch diameter hole in the bottom of the collector so it will fit easily over the screen cones attached to the top of the trap. Then make two more cones as described Step 6 and cement them around the holes in each plastic container. The collectors will then have a cone which will fit over the one on the trap and prevent loss of flies. (See Figures 1 and 1b).
10. Place the screen cones in the collectors over the matching cones on the corners of the trap so that flies have a clear path through matching ½ inch holes from the inside of the box into the inside of the collector. Install a wire or cord across each collector to hold it securely in place.
11. The trap is now ready for placing in a suitable collecting site on the marsh or along a "fly path". After attaching the legs, drive stakes beside two of them and attach the legs to the stakes. This will prevent wind from upsetting the trap.
12. Trap effectiveness can be increased by hanging a decoy beneath the trap. A beach ball 14 to 16 inches in diameter and painted shiny black helps attract flies when suspended beneath the trap. The decoy should clear the ground by four to six inches so it moves with the breeze.
13. The cost of materials for a box trap is reasonable. Even without the use of salvaged or less durable materials, a trap can be built for a few dollars.
My Modifications:
1. I used the single cone method.  After putting the screen on the top of the trap I only used one cone to force he green-heads into the top container.
2. Also in the picture you can see I used a cake box from the local Shop-Rite so that I could empty it out easily after it fills up.
3. In order to keep the boxes on in the wind around here I used two bungy cords that were strung across the box to hold it down.  They hold it down perfectly and don’t move even in the strongest breeze.
4.) Lastly, in order to keep the trap working efficiently the box should be emptied as soon as it starts to fill with dead green-heads.
5.) I have also noticed that if the box is on a decline make sure there is a collector on the low side of the decline as the bugs will tend to fly toward the lower corner.
email me with any suggestions: reservedparking(at)gmail(dot)com
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