Flies are a common pest that can be found in homes and other environments where humans live and work. While many flies feed on rotting material, garbage, and waste, some species of flies do consume blood as part of their diet. Understanding the feeding habits of different fly species can help people take appropriate measures to control populations and prevent the spread of diseases that flies may carry.
Do any flies drink blood?
Yes, some species of flies do consume blood as part of their diet. The most well-known flies that feed on blood are in the families Tabanidae and Culicidae.
The Tabanidae family contains horse flies and deer flies. The females of these species use their sharp, blade-like mouthparts to make a cut in the skin of mammals and birds. They then consume the blood that pools up. Males of these species feed on pollen and nectar.
Species in the Culicidae family are mosquitoes. The females of many mosquito species feed on blood, while males feed on plant nectar. Female mosquitoes use their long, pointed mouthparts to pierce the skin and withdraw blood.
Certain other fly species occasionally feed on blood as well, including some house flies and stable flies. However, blood feeding is not their sole means of nutrition.
Why do some flies drink blood?
Flies that feed on blood do so to obtain protein and iron.
The protein in blood helps female flies develop eggs. Blood feeding occurs either before eggs develop or before eggs hatch. The protein in the blood meal helps stimulates egg production.
Blood also contains iron and other nutrients that help flies stay nourished and healthy.
Male flies do not drink blood, as they do not produce eggs and so do not need the protein. However, some blood feeding fly species can carry diseases from one animal to another, so males may bite without drinking blood.
How do flies drink blood?
Flies that feed on blood have specialized mouthparts for piercing skin and sucking up blood.
Mosquitoes have an elongate, pointed sheath called a proboscis that houses six needle-like parts called stylets. Two maxillae have tiny teeth that help pierce the skin. The other four parts, two mandibles and two maxillae, form tubes that draw blood up from the wound.
Horse flies and deer flies also have blade-like, knife-shaped mouthparts used for slashing the skin. The wound bleeds readily, and the fly laps up the blood. The horse fly’s mouthparts also have a spongelike part for soaking up fluid.
Common blood-feeding fly species
Mosquitoes are likely the most infamous of blood-feeding flies. Different mosquito species have preferences for host species, biting times, and habitats. Some well-known, problematic mosquito species include:
- Aedes aegypti – the yellow fever mosquito, which feeds on humans and spreads dengue fever, yellow fever, Zika, and other diseases
- Aedes albopictus – the Asian tiger mosquito, an invasive species that also feeds on humans and spreads disease
- Anopheles gambiae – one of the major vectors of malaria in Africa
- Culex pipiens – the northern house mosquito that bites birds and mammals and spreads West Nile virus
Horse flies and deer flies
There are over 300 species of horse flies and deer flies in North America. Some common pest species include:
- Tabanus sudeticus – a large horse fly species that aggressively bites livestock animals and humans
- Hybomitra lasiophthalma – a deer fly with dark bands on the wings that bites humans
- Chrysops divaricatus – a small deer fly that feeds on large mammals
The stable fly, Stomoxys calcitrans, occasionally feeds on the blood of dogs, cattle, and humans, in addition to nectar. It is usually more of a nuisance biter than a disease carrier.
The common house fly, Musca domestica, feeds on blood only occasionally. The larvae develop in moist organic material. Blood feeding by the adult flies seems opportunistic rather than necessary. House flies can transmit diseases mechanically on their bodies.
Diseases transmitted by blood feeding flies
Blood-feeding flies ingest disease-causing pathogens during blood meals and can transmit them to other hosts.
Major diseases transmitted by flies that consume blood include:
- Malaria – transmitted by Anopheles mosquitoes
- Dengue fever – transmitted by Aedes mosquitoes
- Yellow fever – transmitted by Aedes mosquitoes
- Zika virus disease – transmitted by Aedes mosquitoes
- West Nile virus – transmitted by Culex mosquitoes
- Lymphatic filariasis – transmitted by Culex, Anopheles, Aedes, and Mansonia mosquitoes
Diseases from other blood-feeding flies
- Bartonellosis – transmitted by sand flies
- Loiasis – transmitted by deer flies
- Onchocerciasis – transmitted by black flies
- Leishmaniasis – transmitted by sand flies
- Trypanosomiasis – transmitted by tsetse flies
Blood feeding flies can also mechanically transmit other pathogens present in the blood from one host to another through their mouthparts.
Are blood-feeding flies dangerous?
Blood-feeding flies can be dangerous by:
- Transmitting diseases – Various viral, bacterial, protozoan, and helminth pathogens can be spread by flies that consume blood from an infected animal and then bite another animal.
- Causing allergic reactions – Proteins in fly saliva that is injected during biting can trigger mild to severe immune reactions in some individuals.
- Causing blood loss – While the amount of blood taken by an individual fly is small, swarms or high populations can lead to anemia and weakness, especially in young animals.
- Spreading infections – The bite wound can get infected by bacteria on the fly’s body.
- Inflicting pain – Bites, especially from species like horse flies, can be very painful.
So while a single fly bite is not necessarily dangerous, high numbers of blood feeding flies pose risks to human and animal health and comfort. Their tendency to spread disease makes them particularly hazardous.
How to control blood feeding flies
Strategies for controlling flies that consume blood include:
Eliminate breeding sites by draining standing water, removing animal waste, and managing garbage. This denies flies egg laying sites and breaks the life cycle.
Install screens on windows and doors to keep flies out of homes and prevent contact with humans and pets.
Use fly paper, jug traps, or other devices to attract and trap adult flies.
Apply insect repellent containing DEET, picaridin, or other approved substances when outdoors.
Wear light colored, long sleeved shirts and pants when exposed to flies outside. Tuck pants into socks.
Apply residual insecticides to surfaces where flies rest. Use larvicides and pupicides to kill immature flies in breeding areas. Follow all label directions carefully.
Release fly predators such as wasps. Introduce Bti bacteria to control larvae in water.
For livestock, provide screened housing, apply repellents, and control breeding areas to protect from biting fly swarms.
While most flies feed on decaying matter, some species do regularly consume blood, especially mosquitoes, horse flies, and deer flies. The females of these flies use their piercing mouthparts to obtain blood from hosts. The blood provides protein for egg production and nutrients for survival. Blood feeding flies can spread diseases and cause other health issues for animals and humans when present in large numbers. Controlling fly populations through sanitation, traps, repellents, and insecticides helps reduce risk. Understanding the feeding behaviors of flies allows people to take appropriate precautions against those known to vector diseases or heavily infest areas.