It is a common experience to find flies persistently buzzing around you. Understanding why this occurs and how to mitigate it involves exploring the types of flies involved and their biological motivations. This article explains fly attraction to humans and offers practical strategies to keep them away.
Identifying the Common Followers
Several types of flies are frequently observed following humans. House flies (Musca domestica) are common, recognizable by their gray to black bodies, four dark stripes on the thorax, and reddish compound eyes. These scavengers are often found near human habitation, attracted to food waste and decaying organic matter.
Fruit flies (Drosophila melanogaster) are small, tan and black insects with red eyes, typically drawn to ripening or fermenting fruits and vegetables. Gnats, a broad category including various small, winged flies, are often gray or black with slender bodies and translucent wings. Deer flies (Chrysops) and horse flies (Tabanus) are larger, aggressive blood-feeding flies. Stable flies (Stomoxys calcitrans) resemble house flies but possess a piercing mouthpart for biting, distinguishing them as blood feeders.
The Science of Attraction
Flies are attracted to humans by a combination of biological and chemical cues. Carbon dioxide, which humans exhale, is a primary attractant. This gas signals the presence of a potential host or food source to many fly species, especially blood-feeding ones. The more active a person is, the more carbon dioxide they release, potentially increasing their attractiveness to these insects.
Body heat also draws flies, as they use thermal cues to locate potential hosts. Sweat and body odor are significant attractants, containing compounds like lactic acid and ammonia. Body odor varies based on genetics, diet, and activities, influencing attraction. House flies, for instance, are drawn to the salt, oil, and dead skin cells on human skin, viewing it as a source of nutrients.
Movement is another factor, particularly for biting flies, which are highly sensitive to moving objects. Bright colors can also attract certain flies. Additionally, some flies, like fruit flies, are drawn to sweet or fruity scents found in perfumes, lotions, and shampoos. Gnats are specifically attracted to moisture and salt, commonly found in sweat and tears, often leading them to hover around faces.
More Than Just a Nuisance
Flies following humans can be more than just annoying. House flies transmit pathogens by landing on decaying organic matter and then on human food. They carry bacteria and viruses, contributing to the spread of food-borne illnesses. House flies also regurgitate digestive enzymes onto food, further facilitating pathogen transfer.
Blood-feeding flies, such as stable flies, deer flies, and horse flies, inflict painful bites. These bites can cause discomfort, swelling, itching, and sometimes allergic reactions. Female horse flies and deer flies have knife-like mouthparts that slice skin to feed on blood, causing visible wounds. These biting flies can also transmit diseases, such as tularemia.
Keeping Flies at Bay
Personal hygiene is important; regular showering and wearing clean clothes can reduce the body odors and sweat components that attract flies. Avoiding strong scents, such as perfumes, colognes, and fruity or floral lotions, can also help, as these fragrances can draw in certain fly species like gnats and fruit flies.
Wearing appropriate clothing can offer a physical barrier against biting flies. Light-colored attire is less attractive to horse flies than dark colors, and long sleeves and pants can protect exposed skin in infested areas. Using insect repellents containing active ingredients like DEET or picaridin provides effective protection against a wide range of flies. Natural alternatives, such as essential oils like lemongrass, lavender, or eucalyptus, may also have repellent properties.
Managing surroundings is crucial. Securing food, promptly cleaning spills, and proper waste management are important, especially for house flies and fruit flies attracted to decaying organic matter and fermenting foods. Eliminating standing water and maintaining a clean outdoor environment reduces breeding sites for many fly species, including gnats and stable flies. Ensuring windows and doors have tight-fitting screens prevents flies from entering indoor spaces.