All horse flies are aggressive and vicious biters, but the bigger ones are particularly menacing. Only the females bite; they require blood meals to be able to produce eggs. ... The flies are also able to track large moving objects, particularly dark colored objects, even while the flies are in fast flight.

Do horse flies follow you?

Besides determination to get blood, there are other reasons horseflies pursue people. For one, they are attracted to moving objects, especially dark moving objects that are warm. So if you start moving away, they follow you.

What happens when a horse fly bites you?

Unlike mosquitoes who release a mild anaesthetic, horseflies don't, which is one of the reasons their bites are so painful. Once the horsefly has locked into your skin, it will suck the blood, causing a sharp burning sensation. In most cases, this will lead to itchiness, inflammation, and swelling around the bite area.