What Do Horseflies Eat? – Diet & Feeding

What does a horsefly eat? Here is all about the diets of this species of insect pests.

One of the things horse flies are known for is their bites which can be painful.

Such bites are likely to cause allergic reactions which may worsen when not properly treated. Whenever these pests are around, it’s necessary to take immediate action in getting rid of them.

Among the things we’ll be discussing is the nutritional need of horseflies. In other words, what do horseflies eat?

This is the basis of our discussion. If you’ve asked this question or seeking answers, we’ve got you covered. Before the end of this article, you should find all the information you seek.

On the other hand, here is what eats horseflies.

Horsefly Diet

Male and female horseflies have different diet requirements.

In other words, their feeding isn’t the same. Male horseflies feed mainly on plant nectar and nectar. Unlike females, male horseflies have weak mouthparts adapted to their type of feeding.

On the other hand, female horseflies feed mainly on blood. If you’ve ever been bitten by a horsefly in the past, now you know that the females were the sole culprits. Female horseflies need to feed on blood to be able to get enough protein for egg production.

Female horseflies are known as aggressive feeders with stinging bites.

What more? All blood sources are welcoming to female horseflies. This includes humans, birds, pets, livestock, and all other mammals they can feed on.

  • How Horseflies Feed

Having provided you with information on what horseflies feed on, it’s necessary to mention or discuss how they feed.

Here, we’re more interested in female horseflies as these are among the most dreaded and will need to be exterminated.

The feeding pattern of female horseflies is very similar to other blood-sucking insects. Here, a potential host is located using visual and chemical cues. In most cases, the carbon dioxide emitted from the body serves to attract them.

Carbon dioxide is produced by all warm-blooded animals. Horseflies (females) home-in on such chemical releases to find their way to a host. Horseflies can detect such chemical releases from long distances.

Apart from the chemical attraction to a suitable feeding host, horseflies are also attracted by visual cues. These range from dark colors, motion, shape as well as size. These, coupled with the former will help horseflies easily navigate their way to a food source or blood.

So, whenever you get bitten, all of the above contributed to locate you.

  • Aggressive Feeders

As soon as they find any source of blood, horseflies (female) immediately descend and dig-in to feed. Any interruption on your part drives them away but only to return almost immediately to commence feeding.

The intensity of feeding makes them not to react as swiftly as ordinary flies do.

As such, you stand a greater chance of killing them as they feed. When horseflies cannot complete their feeding session with a particular host, the next available host is targeted until they’re full.

  • The Feeding Process

Mammalian blood is generally known to coagulate which helps avoid bleeding. This is the body’s natural response to bleeding wounds. However, for horseflies, this situation doesn’t deter them. These pests possess anticoagulants in their saliva which is injected during feeding.

What happens is a situation where such anticoagulants prevent the blood from clotting, thus allowing its free-flow for as long as they feed. For persons with allergic reactions, the injection of coagulants by horseflies may lead to serious health reactions.

A few of the most common allergic reactions include weakness, rash, dizziness, wheezing, swollen lips, and swelling around the eyes. When faced with such, it’s necessary to seek immediate medical assistance.

  • Static Hosts

Bloodsucking horseflies feed better with static hosts than those in motion.

In other words, you’re more likely to get bitten by these pests when static or not moving than when in motion.

However, this isn’t to say that you won’t get bitten at all when moving. The only difference is that there’s a lesser probability of being bitten by them.

  • Bites Maybe Itchy

After feeding on your blood, the bite area becomes itchy. This is probably the body’s defensive response to the anticoagulant injected by the horsefly. Now, scratching of such bite wounds may end up creating a problem.

Excessively scratching the bite area may result in secondary bacterial infections especially when the area isn’t clean. When this happens, it’s best to seek urgent medical attention.

  • Disease Transmission

A lot of questions have been asked about the possibility of horseflies transmitting diseases through their bites. While these concerns are valid and logical, the reality is different.

So far, there has been no conclusive evidence of horseflies transmitting diseases to humans.

While this is true for humans, the same cannot be said for animals. Transmission among animals is much more common. The resulting disease can be quite dangerous resulting in death.

Other symptoms include weight loss and lethargy. A vet doctor should be able to treat such diseases.


We’ve seen that whenever horseflies feed or eat, they cause significant discomfort to both humans and animals.

The best way to tackle or solve the problem is to focus on the cause. This means applying a variety of horsefly extermination measures such as horsefly repellents among others.

A wider treatment of your vicinity goes a long way in helping get rid of horseflies. You may want to discuss with your nearest pest management company on the best possible way to treat a horsefly infestation.

There needs to be sufficient evidence pointing to the presence of horseflies within your surroundings for this step to be taken.


The adoption of preventive treatments is considered the best alternative to stopping horseflies from feeding.

Female horseflies always need blood to feed on to lay eggs and also survive. By covering up exposed parts of your body, you’ll succeed in denying them the opportunity to feed.

We’ve tried to provide answers to an important question; what do horseflies eat.

Here, we’ve seen that the males feed on pollen and nectar while females primarily feed on blood. Females are the most dangerous among the two and cause significant discomfort which may lead to infections among other things.

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