Horseflies with their sharp, painful bites and black flies with their intense, delayed itching: How to deal with mountain insects

Have you ever experienced a sharp, stinging pain or been plagued by intense itching later while enjoying hiking, stream climbing, or camping?
The culprit might be a horsefly or a black fly (also known as buffalo gnats or biting midges).
Both are blood-sucking insects encountered in mountains and along mountain streams, and their swelling and itching can last for two to three weeks.
Here, we explain the ecology of horseflies and black flies and how to deal with them before you head out to the mountains.
*For tick prevention, please refer to here and here.

The difference between horseflies and black flies. They are often mentioned together, but they are actually completely different.

Horseflies and black flies are both insects that often bite people in the mountains.
Both are members of the fly family, and since the adult females approach humans to suck blood, they are often talked about as a pair, but they are actually quite different.
Horseflies are about the size of a bee and are painful the moment they bite, while black flies are as small as fruit flies and you don't notice when they bite, but intense itching follows later..

What happens if you get bitten? (Individual differences apply)

There are significant individual differences depending on your constitution, but the following symptoms often occur.

In the case of horseflies

Because they cut the skin with knife-like mouthparts, you feel a sharp pain that makes you cry out 'Ouch!' the moment you are bitten (based on the author's experience). Bleeding may also occur. After about an hour to a day, the area becomes red and swollen, and the itching continues. For some people, symptoms can last for several days.

In the case of black flies

Many people do not notice while they are being bitten, but from half a day to the next day, intense itching and swelling appear. Depending on the person, the affected area may swell significantly, or rashes and blisters may form.
People who are bitten repeatedly tend to have more severe symptoms.

Both are more likely to cause more severe symptoms than mosquitoes, and scratching them can lead to bacterial infections. If you are concerned about your symptoms, please see a dermatologist.
If you feel you have been bitten, cool the affected area as soon as possible and use insect bite medication.

Measures to avoid being bitten by horseflies and black flies in the mountains: Choosing clothing and insect repellent

1 Wear clothing that does not expose skin

Both horseflies and black flies target exposed skin.
Clothing should basically be long sleeves and long pants, and you should wear socks. In particular, black flies often target the area around the ankles, so tuck your pant hems securely into your socks. It is important not to expose your skin.
Also, horseflies are easily attracted to dark colors, so light-colored clothing such as white or beige is recommended.
Wear a hat and try not to expose your neck as much as possible.

2 Be aware of the places and times where they are likely to occur

Horseflies are often found near streams and in forests during the day, so be mindful of your surroundings when choosing a place to rest.
Black flies are common along clear mountain streams and in damp grassy areas; they are most active in the morning and evening and may attack in swarms.
If there is a management office at your destination, checking the insect situation in advance is one way to prepare.

3. Apply an insect repellent such as the "Pre-Shower DF" series containing Icaridin

Insect repellent is essential for protection against horseflies and black flies.
Apply an Icaridin-based repellent evenly to both your skin and clothing. It is especially effective to carefully treat areas prone to bites, such as the neck, wrists, ankles, and calves.
With an Icaridin-based repellent, you can also treat over your clothes.

4. Utilize "Incense to keep bees and horseflies away from your home"

"Incense to keep bees and horseflies away from your home" is also effective at keeping horseflies and black flies away. Please place it upwind when resting or having lunch.
Contains "Transfluthrin," an active ingredient with excellent diffusion properties. The cross-sectional area is about twice that of standard "Kincho Uzumaki" incense. The effect spreads over a wide area.

Use insect repellent for a comfortable and fun outdoor experience!

Horseflies are characterized by "sharp pain at the moment of the bite," while black flies are known for "intense itching that comes later." Both are easy to encounter in mountains and near streams, and symptoms often linger.
To enjoy hiking and camping comfortably, be sure to take thorough measures by reducing skin exposure and utilizing insect repellent.

* In the mountains, be sure to also be very careful about ticks!