What they are: Greenheads, horseflies, and blackflies are all members of the Diptera, or fly, order. Like mosquitoes, they feed on blood, but they don’t transmit diseases to humans.

Where they are: Greenheads are found primarily near marshes, and horseflies near large animals, while blackflies tend to be near rapidly flowing water.

How to keep them away: Swatting is a time-honored method, but when these flies are particularly persistent or prone to swarming, a repellent can be necessary. DEET works on biting flies, but a better choice is a repellent that contains the chemicals R-326 and MGK-264 as well. Sawyer Broad Spectrum has all three. Most of the natural repellents also work on biting flies, but, again, for a shorter duration. Use fly traps (a popular brand is Arbico Organics) and fly strips (Hot Shot No-Pest Strips) in areas where flies breed, like stables and near swimming pools.

The best way to heal bites: Depending on the type of fly that got you, your bite may itch or sting. For itching, use a topical desensitizer (such as AfterBite). For inflammation, use hydrocortisone (try Cortaid). For stinging, try a topical anesthetic (such as LMX 4%).