Description
The horse fly is a large, sturdy fly measuring 2–3 cm. Only the females bite — they need blood for egg production. They're active in warm, humid weather near livestock and water.
Behavior
Horse flies are persistent and hard to scare off. A bite is sharply painful (the insect literally cuts into the skin). They're most active on warm, still afternoons.
What to do
Cover your arms and legs for activities in meadow areas. DEET spray offers moderate protection. If bitten: clean immediately, cooling helps. Allergic reactions are rare but possible.
Pro tip
Horse flies don't fly in winds above 15 km/h. On still, overcast afternoons near water they're at their most aggressive. Plan demanding hikes on windy days.
Interesting fact
Horse flies can drink 200 mg of blood in a single meal, more than their own body weight. They can smell people and animals from up to 500 meters away.