I found this open source for plans to a fly trap. One of the pictures shows it packed full of flies. Think of what a great source of food this could be for your chickens. I haven't tried it yet, but I thought I'd share.
Basswood (Chap. III., Par. 31).
8 pcs. 3/8"xl"xl2 1/2" S 2 S Sides. 8 pcs. 3/8"xl"x 7 1/2" S 2 S Cross pieces. 5 pcs. 1/2"x3/4"x9" S 2 S Top pes.
Recent investigation has proven that the common housefly is a very dangerous enemy to human life. The fact that it spreads disease and is in every way undesirable is sufficient reason why everybody should be as careful as possible to prevent its increase. One of the most successful ways to wage war on flies is to screen our homes so as to shut them out, and then leave no uncovered garbage pails or any other feeding places for them.
In cities where everybody has been interested in disposing of flies the results have been very encouraging. School children have helped wonderfully by engaging in fly-catching contests.
You can do a great practical good for your own home and community by making this flytrap carefully and using it throughout the fly season.
The House Fly as Disease Carrier, L. O. Howard. Published by F. A.
Stokes Pub. Co., New York. U. S. Bulletin No. 459, and U. S. Bulletin No. 679, House Flies. Insects and Disease, Doane. Henry Holt & Co. Our Household Insects, Butler. Longmans, Green Co. Household Insects and Methods of Control, Bulletin No. 3, Ithaca, N. Y. U. S. Bulletin No. 155, How Insects Affect Health. Fly Traps and Literature. International Harvester Co., Chicago. Winter War on Flies, Willard Price, Technical World, February, 1915. Our Insect Friends and Enemies, John Smith. J. B. Lippincott Pub. Co.
You will probably have to rip your material from stock; select the best surface of your stock for a working face (Chapter II., Paragraph 2); plane one edge for a working edge (Chapter II., Paragraph 4). With the marking gauge, gauge the width of the strips on both surfaces of the stock (Chapter II., Paragraph 6). Rip just outside the line; plane to the gauge lines. Prepare all the side strips in like manner. Saw them the required length. Notice that on two sides of the fly trap, the side strips are narrower than on the other two sides. This is done so the four sides will be equal when assembled. Miter the lower end of each strip, as shown in the drawing.