what do horseflies eat

What Do Horseflies Eat?

Written by: Annemarie Dutton
Last updated on:

Horseflies are true flies and part of the Tabanidae family. They live mainly in humid environments and are often found near ponds, marshes, and streams. Their larvae are predators, collectors and cannibalistic. Horseflies are dangerous to humans. Their bites can cause health problems like severe lesions, fever, and disability in rare cases.

You can generally recognize a horsefly by its size. They can be as long as 1 inch, making them much larger than the average fly.

Diet by Life Stages

Like most other insects, they have three life stages after snatching out of their egg – larva, pupa, and adult. During their first stage, horseflies eat tiny organisms. These include snails, earthworms, insects, crustaceans, and other vertebrae. Even further, they can eat another Tabanidae larva. They have chewing or tearing mouthparts for feeding.

Adults have a different diet from their younger offspring. They rely on plant nectars to obtain the energy needed for flying. Female horse flies require mammal blood for reproduction. Their blood-sucking bites can be very painful to their victims – including humans.

Despite being notorious for their bites and their thirst for blood, their nutrition does require blood at all. The liquid is actually used by females during reproduction.

Although they are unpleasant to people, horseflies have positive attributes. For example, their eyes look majestic – brightly colorful, and on stripes or patterns. Their wings are completely dark, unlike those of deer flies which are patterned.

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Horsefly Bites

Apart from humans, female flies prey on livestock. As the name suggests, horses are one of their favorite targets as well as sheep, cattle, and goats. Bites make an open wound and can cause significant blood loss if they become recurring. Fly repellents can help remove flies that have settled around farms.

In most cases, a bite will cause a raised, red area of skin, which might be painful and sensitive to touch. In extreme cases, bites can cause an allergic reaction that can result in dizziness, swelling, and fluid-filled blisters that become infected.

Females use their sponge-like mouthparts for sucking up blood. Males only feed on pollen and nectar and have similar, but much weaker mouthparts.

Female horse flies usually bite during the day. They are attracted to mammals by movement, carbon dioxide (which mammals breathe out), warmth, and shiny surfaces.

The flies are most active just before sunrise and three hours after sunrise. Another peak in activity is two hours before sunset and just after sunset.

What else do they eat and why are they called horseflies

Adult horse flies feed on nectar and plant exudates, and some are important pollinators of certain specialized flowers; several South African and Asian species in the Pangoniene have spectacularly long proboscis adapted for the extraction of nectar from flowers with long, narrow corolla tubes.

You might be wondering why horse flies are given this moniker. The flies will thrive on horses. They get protein from their blood but also from the moist material around a horse’s eyes. Another reason these fliеs live neаr horsеs is because they reproduce in fresh horse manure, which, of course, is moist and warm.

Are horse flies dangerous?

They are annoying for all animals. It is best to take care of your livestock by removing these pests with chemicals and repellents. They are also harmful – make sure the livestock is protected from insects, parasites, and pests.

There is a high chance of a horse fly causing illnesses to horses. Amongst them are blood diseases like anemia that may spread from horse to horse through fly bites. Although some cases are fatal, diseases are rarely caused by bites. In such cases, consult a veterinarian specialist.

Horseflies are similar to deer flies as both are in the Tabanidae family. The two ways to tell them apart are to look at their overall size and their wings. Horseflies tend to be much larger with a stouter body and a large head with enormous eyes. Their wings are usually clear or cloudy whereas deer flies have dark bands or spots across their wings.

Use vinegar as a natural fly spray for your horse. You can use two cups of vinegar with one cup of water and one cup of bath oil mixed with 1 teaspoon. of Eucalyptus oil. You can also add a teaspoon of citronella oil to this mixture.

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Horseflies on Dogs

Not only can flies annoy dogs, but fly bites can also irritate the skin and cause infections. Getting flies off of your dog and preventing further bites can be as simple as changing your cleaning habits and using everyday cleaners. Grooming your dog often, cleaning your home regularly, and using fly repellants can all keep these pests away from your dog.

Apply petroleum jelly to your dog’s ears. This will prevent flies from landing there again and give your dog’s wounds time to heal. Open bite wounds can attract more flies, so applying petroleum jelly to your dog’s ears is important to prevent more irritation.

Treatment of Horsefly Bites

For any horse fly bite, home care includes not scratching the wound, as this is likely to make it worse and increase the risk of infection. Then, clean the bitten skin with soap and plain warm water using a clean cloth or cotton wool. 

Ease the pain and reduce swelling with a cold compress or ice pack held over the bite for 10 minutes Do not use other remedies aside from plain water and soap. 

Avoiding long grass and not wearing strong odors may help avoid flies in nature. Areas near ponds, lakes, swamps, etc have a high chance of horseflies gathering.

The bite will generally heal in a matter of days. You typically will not experience any adverse side effects. If your bite has not healed within 1 week, or if you’re experiencing unusual symptoms such as dizziness or worsening pain, consult a doctor.


Horsefly larva eats small organisms and other larvae, making them cannibals. Male adults mainly eat fruit nectars, whereas females bite mammals to extract blood. It is required for reproduction. They also drink nectar.

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