Yes, horseflies do bite. Only female horseflies bite, and they do so to obtain a blood meal necessary for the development of their eggs. Their bites are notably painful compared to those of many other insects.
Why Horseflies Bite
Female horseflies require a blood meal to produce eggs. Male horseflies, in contrast, primarily feed on nectar and pollen from plants and do not bite. The female’s mouthparts are specialized for cutting rather than piercing, differentiating their bite from that of a mosquito.
They possess blade-like mandibles and maxillae that saw into the skin, creating an open wound from which they then lap up the pooling blood. Horseflies do not inject an anesthetic when they bite, contributing to the immediate pain felt. They are attracted to cues like movement, heat, and carbon dioxide, which warm-blooded animals, including humans, emit.
Recognizing a Horsefly
Horseflies are larger than common houseflies, measuring between 0.25 to 1.25 inches in length. They have robust bodies that can be gray or blackish in color. A distinguishing feature of horseflies is their large, iridescent compound eyes, which can appear green or purple and sometimes have horizontal stripes. Their wings are usually clear, though some species may have dark bands or patterns. When in flight, horseflies produce a loud, distinct buzzing sound.
Understanding a Horsefly Bite
A horsefly bite results in immediate and sharp pain due to the cutting action of their mouthparts. The bite site shows immediate redness, swelling, and may bleed. A raised welt or bump is a common reaction, similar to other insect bites.
For basic first aid, clean the wound thoroughly with soap and water to prevent infection. Applying a cold compress or ice pack can reduce pain and swelling. Over-the-counter anti-itch creams or oral antihistamines may also relieve discomfort.
Horsefly bites are generally not dangerous. However, increased redness, pus, or fever could signal an infection. Symptoms like widespread rash, dizziness, wheezing, or difficulty breathing warrant immediate medical attention, as these may indicate a severe allergic reaction.
Preventing Horsefly Bites
To minimize the risk of horsefly bites, wear light-colored, long-sleeved clothing and long pants, as horseflies are attracted to darker colors and moving objects. While horseflies can bite through fabric, loose-fitting clothes provide some protection. Using insect repellents containing active ingredients like DEET or picaridin can also deter them.
Horseflies are most active during warm, sunny days, particularly near water sources, woodlands, or livestock. Exercise caution in these environments during peak activity times.