Spotting a Horsefly at the Wildlife Refuge

While doing a photo walk at the Sequoyah National Wildlife Refuge, I came across a large horsefly perched on a blade of Johnson grass. With their huge compound eyes, stout bodies, and nearly inch-long size, horseflies are quite intimidating insects. This robust fly was no exception. As a wildlife photographer, I’m always seeking interesting creatures to capture through my lens. So when I noticed this formidable horsefly, I swiftly moved in and snapped a few photos before it darted off. Getting decent shots of horseflies can be tricky given their wariness and fast flying speed. Luckily, this one stayed still just long enough for me to freeze its image.

Horsefly on a Blade of Grass
Horsefly on a Blade of Grass

While notorious for their painful bites, horseflies are still fascinating subjects, especially up close. Their intricate wings, patterns, and eyes reveal the beauty and complexity of even pesky insects. For a wildlife photographer like me, all creatures great and small can make intriguing photo subjects.

Steve Creek, Wildlife Photographer

Anatomy of a Horsefly

Horseflies, scientifically known as Tabanidae, are large and robust insects. Their distinctive features include:

1. Size and Coloration

Horseflies typically measure between 0.5 to 1.25 inches in length, making them some of the largest flies in the world. They are often dark in color, with some species sporting striking patterns.

2. Mouthparts

One of the most remarkable aspects of horseflies is their mouthparts. Equipped with scissor-like mandibles and a sponge-like labium, they can inflict painful bites on their hosts. Unlike mosquitoes, female horseflies use their mouthparts to lacerate the skin and feed on blood.

3. Eyes

The compound eyes of horseflies are truly a marvel. They are exceptionally large and well-developed, giving these insects excellent vision. This adaptation helps them locate potential hosts from a distance.

The Life Cycle

Understanding the life cycle of horseflies provides insight into their ecological significance:

1. Egg Stage

Horseflies lay their eggs near water bodies, such as ponds or streams. The larvae, known as “nymphs,” hatch from these eggs and live in aquatic environments, where they feed on other aquatic organisms.

2. Larval Stage

During the larval stage, horseflies are voracious predators, preying on small invertebrates in the water. This predatory behavior contributes to the regulation of aquatic ecosystems.

3. Pupal Stage

After the larval stage, horseflies enter the pupal stage. Here, they undergo metamorphosis and transform into their adult form.

Behavior and Feeding Habits

Horseflies are known for their aggressive feeding habits, which serve important ecological roles:

1. Blood-Feeding

Female horseflies are blood-feeders, and they require blood to reproduce. They are attracted to warm-blooded animals, including humans, livestock, and wildlife. Their bites can be painful and sometimes transmit diseases.

2. Pollination

While their blood-feeding habits are notorious, horseflies also play a role in pollination. Some species are effective pollinators of various plants, aiding in the reproduction of flowers and the production of fruits.

Ecological Importance

Horseflies might seem like pests due to their bites, but they have significant ecological importance:

1. Population Control

As larvae, horseflies help control the populations of smaller aquatic organisms. This regulation maintains the balance of ecosystems.

2. Pollinators

Certain plant species depend on horseflies for pollination, ensuring the survival and diversity of these plants.


In the intricate web of life, every species has its role, no matter how imposing or fearsome it may appear. Horseflies, with their large size and painful bites, are essential components of various ecosystems. Understanding their biology and ecological contributions can foster a deeper appreciation for these remarkable insects.


Are all horseflies blood-feeders?
No, only female horseflies feed on blood, while males primarily feed on nectar and plant juices.

Do horseflies transmit diseases like mosquitoes?
Although horseflies can transmit diseases, their role as disease vectors is less significant compared to mosquitoes.

Are there ways to prevent horsefly bites?
Wearing protective clothing and using insect repellents can help reduce the risk of horsefly bites.

How long do horseflies live?
The lifespan of a horsefly varies depending on the species but generally ranges from a few weeks to a couple of months.

Can horseflies be beneficial in any way?
Yes, some species of horseflies contribute to pollination, benefiting various plants in their ecosystems.

Image Information:

  • Date: 9/10/23
  • Time: 8:22:19 AM
  • Camera: Canon EOS R5
  • Lens: Canon RF 100-500 mm F4.5-7.1 L IS USM
  • ISO: 800
  • Aperture: 8
  • Shutter: 1/800
  • Exp. Comp.: +0.3
  • Program: Manual

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