Flies often prompt questions about their interactions with humans, particularly whether they bite or sting. While some flies are merely a nuisance, others can inflict painful bites by drawing blood from humans and animals. Understanding their feeding mechanisms is key to identifying and managing encounters with these insects.
Understanding Fly Mouthparts
The ability of certain flies to bite stems from their specialized mouthparts, designed for piercing and sucking. Unlike insects such as bees or wasps, flies lack a stinger. Biting flies, typically the females, possess a proboscis adapted to cut into skin and access blood vessels. This feeding strategy is necessary for many female flies to obtain protein for egg development.
While many flies have sponging mouthparts suitable for lapping liquids, biting flies have more complex structures. These include blade-like or scissor-like components used to lacerate skin. Once the skin is cut, they use other mouthparts to soak up the pooling blood. Flies cannot inject venom like stinging insects.
Flies That Bite: Common Culprits
Several types of flies are known to bite humans, each with distinct characteristics and bite sensations.
Horse Flies
Horse flies are relatively large insects that inflict a notably painful bite. They use scissor-like mouthparts to cut into the skin, causing immediate, intense pain and often a raised, red, and itchy welt. This pain is exacerbated because they do not release an anesthetic when biting.
Deer Flies
Deer flies are smaller than horse flies but similarly aggressive. They possess blade-like mouthparts that slice the skin. Their bites are painful and typically leave an itchy, red area with swelling. These flies often target the head and upper body.
Stable Flies
Stable flies resemble house flies in size and appearance. They deliver a sharp, needle-like bite, primarily targeting the legs and ankles. Both male and female stable flies bite, and their bites can cause a pinching sensation, leading to red rashes and small, raised red bumps.
Black Flies
Black flies, also known as buffalo gnats, are small, hump-backed insects. They generally bite around the head, ears, or neck. Their bites create a small puncture wound and can result in significant swelling, itching, and sometimes bleeding.
Sand Flies
Sand flies are tiny, hairy flies that inflict painful, itchy bites. These bites often cause red bumps and blisters, which can develop into fluid-filled blisters and itch intensely, sometimes with a burning sensation.
What Happens After a Fly Bite?
Following a fly bite, individuals typically experience localized reactions such as itching, swelling, and redness around the affected area. The pain associated with the bite can vary depending on the fly species and the individual’s sensitivity. These symptoms are usually a response to the fly’s saliva, which may contain anticoagulants to keep blood flowing during feeding. Scratching the bite can exacerbate irritation and potentially lead to secondary bacterial infections.
Most fly bites are generally harmless and resolve within a few days. However, some individuals may experience more pronounced reactions. Allergic responses can occur, ranging from increased swelling and redness to more widespread symptoms like hives, wheezing, or dizziness. Severe allergic reactions warrant immediate medical attention.
Some biting flies can act as vectors for disease-causing agents. However, for most common fly bites, the risk of disease transmission to humans is generally low.
Minimizing Fly Bites and Managing Reactions
Preventing fly bites involves several practical strategies to reduce exposure.
Prevention
Wear protective clothing, such as long-sleeved shirts and pants, to cover exposed skin, particularly in areas with high fly activity.
Use insect repellents containing active ingredients like DEET or picaridin on exposed skin to deter biting flies.
Avoid certain outdoor areas known for large fly populations, especially during peak biting times like early morning or late afternoon.
For homes, ensure windows and doors have intact screens to prevent flies from entering indoor spaces.
Managing Bites
If a bite occurs, prompt first-aid measures can help manage symptoms.
Clean the bite area gently with soap and water to reduce the risk of infection.
Apply a cold compress or ice pack to the bite for 10 to 20 minutes to help reduce swelling and pain.
Use over-the-counter topical treatments, such as hydrocortisone cream or calamine lotion, to alleviate itching and discomfort.
Oral antihistamines may also be taken to reduce itching and swelling.
If the bite area shows signs of infection, such as increasing pain, redness, or pus, or if severe allergic reactions develop, seeking medical attention is advisable.