The contraption has received a huge response from the community and has been picked up by many mosquito-control districts. The trap, in its most basic form, is a beach ball spray-painted black, covered with the adhesive Tanglefoot and hung from a ceiling or tree branch in a yard. Cilek suggests the adhesive Tanglefoot can either be purchased separately and then applied to a beach ball or in a kit available at a hardware store. The yellow fly is a fairly robust insect, and if you have 10 or 20 trying to get at you, they're going to pester the daylights out of you until you run away or swat them. They are always aggressive because looking for a blood meal, that's just the nature of the beast.
Yellow fly is another name for deer fly.
There are about 12 to 15 species of the yellow fly and about 40 species of the deer fly, including the biting yellow flies, Cilek said. The female yellow flies are the only ones that feed on blood. They develop a pool of blood and then lap it up, but in order to keep the blood flowing they have to inject an anticoagulant, which is what causes the inflammation and ensuing irritation. Just make sure, though, use a meat tenderizer without salt. The yellow fly is seasonal and this is the height of its season.