Step 1: Disassemble Zapper
Any electronic bug zapper of any size will do. Zapper consists of two concentric cylinders made of coarse metal screen and fluroescent bulbs that attract some kinds of bugs. Mosquitos are attracted to warm-blooded mammals, however, and this project adds a sleeve of heavy black plastic to the outside of the inner zap screen. The bulbs heat the plastic sleeve, which attracts the mosquitos. Plastic sheet is an electrical insulator, but the machine will still zap with it in place.
Remove The protective plastic cage and remove the light bulbs. If these steps do not also remove the top electronic cover, leave it in place, no modifications to the electronics are necessary. Unsolder the wire that comes from out of the top of the unit and attaches to the top of the outer wire zap screen. Carefully remove the outer zap screen and any ceramic spacers. Cut heavy black plastic, such as 6 mil landscaping plastic, to a size and shape that will go around the inner zap screen once with a some overlap. Secure the plastic to the inner zap screen using an ordinary office stapler as far up as you can reach with it. If the top of the plastic needs securing, make a complete wrap of electrical tape around it, plus some overlap.