What do they look like?
Why are they dangerous?
Female horseflies have sharp cutting parts which can even saw through the skin of an ox, enabling them to drink their blood. Only the females bite, as they need protein to produce their eggs: the males feed solely on plants. The photograph above of a horsefly beneath a leaf is a female laying her eggs on its underside.
The females’ bites are extremely painful. In some countries, they spread a variety of serious and potentially fatal diseases. Luckily in Britain they do not spread any dangerous diseases, but their bites can still become infected and cause very nasty reactions.
Symptoms of a horsefly bite:
- a large red, raised rash (called hives or urticaria)
More serious symptoms:
- part of your body becoming puffy and swollen, including around the eyes or lips.
- Some people are allergic to horsefly bites which can cause painful hives and in some cases, people can experience anaphylactic shock.
There can also be complications:
- Horseflies can transmit bacterial infections.
- If the skin continues to stay red and swollen or if moisture seeps out, keep an extra eye on it.
- Wash the area thoroughly twice a day with water and soap or disinfect it with alcohol.
- Horsefly bites can take a while to heal and can become infected. See your GP if your wound does not begin to subside after a few hours, or if you have symptoms of an infection, such as pus or increasing pain, redness, heat or swelling.
DID YOU KNOW? Since ancient Greek times, horseflies have featured in literature as way of tormenting people to the point of insanity. In ancient Greek mythology, the gods would sometimes send them after their enemies as a punishment.
How can I avoid them?
Horseflies are often found near water, so be alert. Do not pitch tents near ponds or large bodies of water, especially stagnant water.
Horseflies are active in sunlight but they avoid shady places and do not fly at night.
What to do if one bites me?
- Cool the area of the horsefly bite with a wet cold washcloth, a coolpack or some ice cubes in a flannel or a plastic bag.
- Disinfect the bitten area by washing thoroughly with water and soap or treat it with (for example) alcohol. Disinfecting with vinegar is also an option.
- Keep an eye on the bitten area for a few days. There’s a small chance a bacterial infection might occur. If the area stays red or you see yellow crustiness, then consult your GP.
- Treat the area with medication. Pharmacies sell several treatments for insect stings and horsefly bites.
- Take an antihistamine tablet (e.g. one you use for hay fever) to reduce the itching and allergic reactions.