If bitten, the doctor recommends using a topical anesthetic such as benzocaine or lidocaine to reduce itching. And an antihistamine such as Benadryl or hydrocortisone such as Cortaid can reduce swelling. 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. We know yellow flies are attracted to movement and carbon dioxide because they think moving objects may be a possible blood meal, which it needs to survive. Cilek suggests the adhesive Tanglefoot can be purchased separately and then applied to a beach ball or in a kit available at hardware stores.
Yellow fly is really another name for deer fly.
There are about 12 to 15 species of the yellow biting 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. When they bite, the system is a sort of cut and slash sort of thing. 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, to use a meat tenderizer without salt.