Nearly everyone has experienced the annoyance of a fly, but have you ever wondered if that common house fly buzzing around is capable of biting? While house flies are more known for their nuisance than their bites, there are numerous other fly species that are indeed biters. This article will delve into the world of biting flies, exploring the types that bite, why they do it, and how you can protect yourself.
While mosquitoes are often the first culprits that come to mind when we think of biting flies, this article will focus on other types of flies that bite, offering a comprehensive guide to understanding and managing these pesky insects.
What Exactly is a Fly?
Flies are insects characterized by having only two wings, unlike most winged insects which possess four. A fly’s mouthparts are specifically adapted for their feeding habits. In many cases, these mouthparts are designed for sucking up liquids. However, in biting flies, they are also equipped for piercing skin to obtain blood meals.
Similar to mosquitoes, biting flies are adept at locating their hosts – humans and other animals – through a variety of sensory cues. They are attracted to:
- Carbon dioxide and moisture in exhaled breath: These are key indicators of a living, breathing host.
- Dark colors and movement: These visual cues help flies identify potential targets.
- Warmth and perspiration: Body heat and sweat are further attractants for biting flies.
Once a biting fly identifies a suitable host, it uses its piercing mouthparts to puncture the skin. To ensure a steady flow of blood, the fly injects saliva containing an anticoagulant. This saliva, while facilitating blood feeding for the fly, can also cause irritation and allergic reactions in sensitive individuals, sometimes even triggering severe, life-threatening responses.
Beyond the immediate discomfort of their bites, biting flies pose a significant health risk globally. They are vectors for numerous debilitating diseases, affecting millions of people worldwide. For instance, sand flies (Psychodidae) are responsible for transmitting sand fly fever, bartonellosis, and leishmaniasis in various regions around the globe. In the United States, the deer fly (Chrysops discalis) is known to transmit tularemia. Biting midges (Ceratopogonidae) are vectors of various diseases and can infect livestock with bluetongue virus in the U.S. Additionally, bites from black flies (Simuliidae), horse flies (Tabanidae), and stable flies (Stomoxys calcitrans) can induce severe allergic reactions in some individuals.
Identifying Common Biting Flies
To effectively manage and prevent bites, it’s crucial to identify the types of biting flies you might encounter. Here are some common culprits:
Deer Flies and Horse Flies (Tabanidae)
Deer flies hold the unfortunate distinction of being among the few types of flies in the United States that transmit diseases to humans. They are vectors of tularemia, also known as “rabbit fever,” a bacterial disease that can be contracted through contact with infected animals or objects, tick bites, and occasionally, deer fly bites from Chrysops discalis.
Deer flies are most prevalent during the spring season. They are medium-sized flies, approximately ¼-inch in length, roughly the same size as a house fly. Their coloration typically ranges from yellow-brown to black, often featuring distinctive dark bands on their wings. A striking characteristic of some deer flies and horse flies is their iridescent green eyes.
Deer fly larvae, resembling maggots, are aquatic, developing in water. Adult deer flies are commonly found near streams, lakes, ponds, marshes, and swamps, especially along trails. They can be quite bothersome, buzzing around people’s heads, particularly in areas with high populations. Both deer flies and horse flies employ scissor-like mouthparts to bite, cutting into the skin and lapping up the resulting blood flow. This relatively crude feeding method can make their bites quite painful.
Horse flies are larger than deer flies, reaching an inch or more in length. Their coloring varies, with some being entirely black, while others, known as “greenheads,” are light brown with bright green eyes. Horse flies are strong, fast fliers that primarily feed on the blood of livestock and other animals. Similar to deer fly larvae, horse fly larvae typically develop in aquatic or moist environments, preying on other insects before migrating to drier soil to pupate. Their life cycle can extend up to two years.
Stable Fly (Stomoxys calcitrans)
The stable fly, about ¼-inch long and gray with four dark stripes on its thorax (the area behind the head), bears a strong resemblance to the common house fly. However, a key distinguishing feature is its pointed proboscis located beneath its head, which it uses to suck blood. Stable flies are most abundant in late summer and fall. They are known to travel several miles to find hosts, biting livestock (hence their name), pets, and humans. They typically bite in the early morning or late afternoon, often targeting ankles and inflicting a sharp, stabbing pain.
Stable flies lay their eggs in decaying vegetable matter such as haystacks, grass clippings, manure, and shoreline vegetation. Both adult and larval stable flies are nearly identical to house flies in appearance.
Black Flies (Simuliidae)
Adult black flies are small, measuring no more than 1/8-inch in length, with broad wings and a characteristic humpbacked appearance. Like other biting flies, black flies thrive in moist environments and are often found near creeks and rivers where their larvae attach to submerged stones. They are also known as “buffalo gnats.”
Black flies are capable of flying up to 10 miles in search of a blood meal. While they do not transmit diseases to humans in the United States, their bites can pose a threat to livestock and even humans when present in large numbers, typically in late spring and early summer. Fatalities have been reported due to allergic reactions, blood loss from numerous bites, and even from inhaling the flies. Black fly bites often result in significant swelling, bleeding, itchiness, and slow healing. They prefer to bite on the head and areas where clothing fits tightly.
Biting Midges (Ceratopogonidae)
Biting midges, often confused with non-biting midges (Chironomidae) which are larger and resemble mosquitoes but do not bite, are significantly smaller, measuring no more than 1/32 of an inch long. They are also known by various names including “punkies,” “no-see-ums,” or simply “gnats.” Their minute size allows them to penetrate standard window and door screens. Biting midges can be serious pests, particularly along the shores of oceans, lakes, ponds, and rivers, biting both during the day and at night.
The larvae of biting midges, which are tiny and worm-like, live in moist sand or soil, decaying vegetation, tree holes, and other damp locations, often near the edges of ponds, marshes, and lagoons. Some species feed on human blood, while others target insects, including mosquitoes.
Sand Flies (Psychodidae)
Sand flies are related to non-biting drain flies. Their larvae are tiny and worm-like, inhabiting moist decaying plant matter, moss, mud, or water. Adult sand flies are long-legged, no more than 1/8-inch long, hairy, and range in color from brown to gray. They have wings that form a distinctive “V” shape when at rest.
Most sand fly species feed on the blood of mammals, reptiles, and amphibians, typically at night. In various parts of the world, including southern Texas in the United States, certain sand fly species (Lutzomyia) are suspected vectors of cutaneous leishmaniasis, a disfiguring protozoan disease in humans.
Managing Biting Flies Around Your Home and Property
Controlling biting flies across a large area can be challenging due to the concealed larval habitats and the ability of some adult flies to travel considerable distances from their breeding sites. However, several strategies can be employed to manage biting flies, particularly around your home and property:
Sanitation: Eliminating breeding sites is a crucial step in controlling certain biting flies. For example, stable fly larvae thrive in decaying hay, straw, and other vegetation, including manure mixed with plant matter. Removing these potential larval development sites can significantly reduce stable fly populations. Similarly, disposing of decaying vegetation can help control biting midges and sand flies.
Exclusion: Preventing flies from entering structures is another effective method. Stable flies are known to enter buildings in search of blood meals. Ensuring that screens are installed and well-maintained on windows and doors can help keep them out. For smaller biting flies like midges, finer mesh screens may be necessary.
Pesticide Application: Pesticides can play a role in biting fly control, but their use is often limited. Ultra-low volume (ULV) treatments and space sprays of non-residual pesticides can be effective in areas with high fly concentrations, providing immediate relief. However, these treatments only kill flies on contact and break down quickly, offering limited long-term protection. Residual pesticides can be applied to surfaces where flies rest, such as vegetation, barn walls, and exterior house walls. However, this method is only effective if flies actually land on treated surfaces.
Larviciding: Targeting fly larvae with larvicides can be an effective control method. Formulations containing Bacillus thuringiensis (BTI) or growth regulators like methoprene have been successfully used against mosquito larvae in stagnant water. BTI has also been used to control black fly larvae in streams.
Preventing Biting Fly Bites
When management strategies aren’t enough, personal protection becomes essential to avoid bites.
Repellents: Insect repellents are your final line of defense. Repellents containing DEET (N,N-diethyl-meta-toluamide) or picaridin are considered most effective. While effective against mosquitoes, they may be less potent against certain biting flies.
Protective Clothing: Supplement repellent use with protective clothing. Wear heavy-duty, light-colored clothing, including long-sleeved shirts, long pants, and hats. When black flies are abundant, head nets like “bee bonnets” can offer crucial protection.
Avoidance: Minimize exposure by avoiding areas known to be heavily infested with biting flies, especially during peak biting times. Smaller flies like biting midges may also be deterred by applying heavy lotions or oils to the skin, which can trap them. Fans can also be useful in keeping small areas free of flies, particularly smaller species whose flight is affected by air currents. Similarly, smoke from candles or torches can help repel smaller species.
While complete eradication of biting flies is often unrealistic, combining preventative measures with fly management strategies can significantly reduce bites and minimize the nuisance and health risks associated with these vexing pests.
Disclaimer: When using pesticides, always read and adhere to product label directions. The information provided here is for general guidance and may not be applicable to all situations. Consult with local public health or pest control professionals for specific advice.
Image Credits: Photos and illustrations are courtesy of the U.S. Centers for Disease Control and Prevention, Alex Wild (University of California, www.myrmecos.net), Jim Kalisch (University of Nebraska), and Ohio State University.
