Flies are often seen as mere buzzing nuisances, flitting around food or lights. However, this overlooks a key aspect of their behavior: while many are harmless scavengers or pollinators, a distinct group can bite. The world of flies is diverse, with varied feeding habits that impact humans and animals.
The Biting Truth: Not All Flies Are the Same
Not all flies bite. Non-biting flies, such as common house flies or fruit flies, have sponging mouthparts designed to soak up liquids from surfaces and cannot pierce skin. These species are often attracted to decaying organic matter or ripe produce for feeding.
Conversely, biting flies have specialized mouthparts that allow them to penetrate skin and feed on blood. This blood-feeding, known as hematophagy, is essential for female biting flies, as they require a protein-rich blood meal to develop their eggs.
Identifying Common Biting Flies
Horse flies, up to an inch long with green or black eyes, are known for their painful bites due to mouthparts that cut into the skin. Deer flies, slightly smaller with patterned wings, also inflict painful bites and often target the head or upper body. Both are frequently found near wooded areas and water.
Stable flies resemble common house flies but have a pointed, piercing proboscis, delivering sharp, stabbing bites, often targeting ankles and lower legs. They are prevalent around livestock and agricultural settings. Black flies, also called buffalo gnats, are small, hump-backed flies that swarm and cause itchy, swollen bites, especially near running water. Tiny sand flies, about one-eighth of an inch and active from dusk till dawn, can cause painful, itchy bumps and blisters.
The Purpose and Impact of Fly Bites
Female biting flies primarily bite to obtain a blood meal, essential for the maturation of their eggs. Some species, like horse flies and deer flies, use scissor-like mouthparts to cut the skin, creating an open wound from which they lap up blood. Other species, such as stable flies and black flies, have piercing mouthparts that inject anticoagulants and pain-killers to facilitate blood flow and reduce detection.
The immediate impact of a fly bite can range from mild irritation to significant discomfort. Bites commonly result in sharp pain, redness, itching, and swelling, often forming a raised welt or bump. In some individuals, the injected saliva can trigger allergic reactions, leading to more widespread skin reactions, dizziness, or even wheezing. While most bites are not serious, certain species can transmit pathogens, such as deer flies transmitting tularemia, and sand flies transmitting leishmaniasis.
Protecting Yourself from Biting Flies
Wearing light-colored, long-sleeved shirts, long pants, and a hat can cover exposed skin, as biting flies are attracted to dark colors and cannot bite through clothing. Avoiding peak activity times, such as dawn and dusk for some species, and minimizing time in known fly habitats like swamps, marshes, or areas with livestock can reduce exposure.
Applying insect repellents containing active ingredients like DEET or picaridin to exposed skin offers protection. Plant-based essential oils, such as oil of lemon eucalyptus, lavender, or citronella, are also recognized for their repellent properties. Maintaining a clean outdoor environment by reducing decaying organic matter and standing water can help minimize fly breeding sites.