Horse flies are a common nuisance to humans and animals alike, known for their painful bites and persistent behavior. These insects can be found in various parts of the world, often near bodies of water where they lay their eggs. Their size can vary, but typically, they are considered moderate to large flies.
Adult horse flies, in general, measure between 14 to 19 mm long, with clear wings and a grayish-brown thorax. On the other hand, smaller relatives called deer flies measure between 10 to 13 mm in length, and have wings that are tinted smokey gray-brown or with dark patterns, along with a greenish-yellow thorax that features dark stripes 1. These size differences, as well as the color variations, can help in identifying and distinguishing between horse flies and deer flies.
By understanding the size and appearance of horse flies, people can take appropriate measures to protect themselves and their animals from these bothersome pests. Whether it’s through the use of repellents, traps, or other methods, managing their presence can lead to a better outdoor experience for all.
Horse Flies Identification
Size and Appearance
Horse flies are considered moderate to large flies, measuring between 14 to 19 mm in length. They have a stout body shape and are usually medium to large in size, making them easily distinguishable from other fly species.
Some key characteristics of horse flies include:
- Moderate to large size (14-19 mm)
- Stout body shape
- Clear wings
- Grayish-brown thorax
Color and Wings
Horse flies’ coloration is mostly drab browns, grays, and blacks. Their wings are generally clear, which contrasts with their dark-colored bodies. In some cases, they may have wings that are solidly colored or display dark patterns.
Eyes and Antennae
One of the most distinguishing features of horse flies is their large, brightly colored eyes, often displaying horizontal stripes. Additionally, as part of the Tabanidae family, their antennae are relatively short compared to other flies.
Male vs Female Horse Flies
It’s important to differentiate between male and female horse flies, as only female horse flies are known for biting. Female horse flies have a proboscis used for piercing skin and feeding off blood, whereas male horse flies have mouthparts suitable for feeding on nectar from flowers.
Here’s a comparison table of male and female horse flies:
| Male Horse Flies | Female Horse Flies |
|---|---|
| Feeds on nectar | Bites and feeds on blood |
| Mouthparts for flower feeding | Proboscis for piercing skin |
| Non-aggressive | Aggressive when seeking a blood meal |
When identifying horse flies, it’s helpful to consider these attributes alongside factors, such as their size, color, and environment, to correctly determine the fly’s specific identity, while also acknowledging regional variations of fly species.
Horse Flies Behavior
Biting Habits and Pain
Horse flies are notorious for their painful bites, which are caused by their unique mouthparts. The female horse fly’s mouthparts are designed to cut through skin and draw blood from animals and humans alike. Some common victims of horse fly bites include:
- Cattle
- Horses
- Humans
Not only are the bites painful, but they can also cause swelling and allergic reactions in some people. Males, on the other hand, do not bite as they feed on nectar.
Comparison of Horse Fly Bites
| Male | Female |
|---|---|
| Do not bite | Bite painfully |
| Feed on nectar | Feed on blood |
Blood, Nectar, and Pollen Diet
While female horse flies primarily feed on the blood of their victims, the male horse flies consume nectar from flowers. This difference in diet is due to the different roles each gender plays in the horse fly lifecycle:
- Male: Pollinator
- Female: Requires blood for egg development
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Life Cycle and Breeding Grounds
The typical horse fly life cycle consists of four stages:
- Egg
- Larva
- Pupa
- Adult
Female horse flies lay their eggs on plants or other surfaces near suitable larval habitat, such as:
- Wetlands
- Ponds
- Marshy areas
Horse flies have relatively brief lifetimes, with the entire lifecycle typically completed in one summer season.
Habitats and Seasonal Activity
Horse flies are most active during the summer months and can be found in various outdoor habitats, including:
- Wetlands
- Forests
- Meadows
They are often attracted to livestock and other animals in barns or pastures, making them a significant pest for farmers and property owners. To reduce horse fly activity, it is recommended to:
- Provide shelters or canopies for animals (Penn State Extension)
- Avoid areas with high horse fly populations
- Turn livestock out at night rather than during the day, as horse flies are primarily active during daylight hours
Prevention and Control
Protecting Livestock and Pets
Protecting your livestock and pets from horse flies is important to prevent painful bites and allergic reactions. One way to protect animals is by providing them shelter in barns, which have screens on windows and doors to prevent the horse flies from entering. Examples of other measures include:
- Using fly-resistant mesh blankets for horses
- Applying pet-friendly repellents on dogs and rabbits
Ways to Repel Horse Flies
Several methods can be used to repel horse flies. Here are a few options:
- Essential oils: Some people use essential oils, such as eucalyptus and citronella, to repel horse flies.
- Plants: Growing plants around your home that have strong scents can help deter horse flies, for example, basil, lavender, and lemongrass.
- Carbon dioxide traps: Horse flies are attracted to carbon dioxide, so using traps that emit CO₂ can lure them away from humans and animals.
Fly Traps and Insecticides
Another way to control horse flies is with fly traps and insecticides. A popular type of trap is the sticky trap, which captures horse flies on a sticky surface. Insecticides like pyrethrin can be sprayed around the property to help reduce horse fly populations.
Fly Traps and Insecticides Comparison:
| Method | Pros | Cons |
|---|---|---|
| Fly Traps | Environmentally-friendly; Easy to maintain | May not catch all horse flies |
| Insecticides | More effective at reducing populations | Use of chemicals |
Keep Your Property Horse Fly-Free
Managing your property can play a significant role in preventing horse fly infestations. Here are some steps to follow:
- Eliminate damp areas around your yard, as horse flies breed in moist, organic debris.
- Keep swimming pools clean and properly chlorinated.
- Regularly maintain landscape, including trimming tall grasses and bushes.
In summary, controlling horse flies involves a combination of protecting animals, using repellents and traps, and maintaining your property. Proper management can help keep your home and surroundings free from horse flies and ensure the safety of your livestock, pets, and yourself.
Horse Flies in Literature and Science
In literature, horse flies have been mentioned by ancient Greek playwright Aeschylus in his works. They are often portrayed as persistent and annoying creatures.
In science, horse flies are known for their multicolored appearance and their roles as disease vectors. They transmit pathogens through their bites, causing potential health risks to humans and animals.
Horse flies can impact livestock, especially affecting milk output. This is due to the stress caused by their bites, which results in reduced milk production in cattle.
Their preferred breeding grounds are typically areas with damp soil and water. This helps ensure their reproductive success and population growth.
Features of Horse flies:
- Multicolored
- Disease vectors
- Impact on livestock
- Preference for damp breeding grounds
Some characteristics of horse flies that allow them to thrive as disease vectors include their resilience and strong flight capacity. This enables them to cover large distances, ensuring their continued existence and spread of pathogens.
Comparison table:
| Characteristics | Horse Flies | Deer Flies |
|---|---|---|
| Size | Approximately 1″ | Smaller, about 0.4″ |
| Color | Multicolored | Dark bands on wings |
| Disease Vectors | ✅ | ✅ |
| Breeding Grounds | Damp soil and water | Similar to horse flies, damp soil, and water |
By examining the role of horse flies in literature and science, we’ve seen their enduring presence and impact throughout history. Their influences on both human and animal health, as well as their distinct traits, have made them a subject of interest across disciplines.
Footnotes
28 Comments. Leave new
Always happy to contribute to your site! One of the web’s best. 🙂
Thank you for your support.
i found one in my room and it is a male happy i put it in a clear cup with a lid and finding out some very cool things about it
bite sized protein snacks.
What an interesting post! Love to read all the discussion about it!
It’s taken me a while to track this down! It’s what bit me on the Leg today in the garden. Visiting a non-stock farm and Garden plants – bare ground and inspecting some fruit bushes. NOT a wasp, Bee, or Horsefly…. and none of the rest as are commonly offered as common UK Biting insects. Bumble & Honey Bees are busy so knew it wasn’t them. Continued to harass me – thought it was protecting a Nest in the ground, etc. Weather cool today but Clear sky with cool breeze at Sea-Level N of Inverness today. The Foto fairly confirms what I saw – = like a LARGE Bluebottle with Striped Abdomen and Wings as you see.
I have just had one of these huge things land in my garden. I am really allergic to horse fly bites and have never seen one this big. I am sure its a female too!
We are in leafy (boggy) Bedford Town and I am really surprised to see it here.
I know we have smaller ones in the forests around here but this is a huge surprise – I am keeping it under a glass until I can pluck up the courage to set it free.
I have just had one of these huge things land in my garden. I am really allergic to horse fly bites and have never seen one this big. I am sure its a female too!
We are in leafy (boggy) Bedford Town and I am really surprised to see it here.
I know we have smaller ones in the forests around here but this is a huge surprise – I am keeping it under a glass until I can pluck up the courage to set it free.
I have somthing that I feel inside my ears, nose and especially my hair. I have tons of pictures but I continue to battle whatever this is inside my body and out. May I please send you some pictures I’d be happy to pay for your knowledge. I would appreciate it so much if you could take a look see if you recognize anything.
I appreciate your consideration.
Shelley Deitz
I have somthing that I feel inside my ears, nose and especially my hair. I have tons of pictures but I continue to battle whatever this is inside my body and out. May I please send you some pictures I’d be happy to pay for your knowledge. I would appreciate it so much if you could take a look see if you recognize anything.
I appreciate your consideration.
Shelley Deitz
There’s about 20 of these on an apple tree in a friend’s garden neer a river.
West Wales.
Just had one in my house. Im in West Wales too. Huge thing, scared the life out of me!
Just got in my conservatory been told it’s giant dark horse fly ???? not boggy here but a pond few hundred m away and horse fields very close to be expected
Interesting Info about these odd sitings – of an rare insect. Once upon a time I was in contact with our local SAC( like ADAS) but those days are lonnnng since gonnn! Pity that Aacademia doesn’t keep an eye on these websites / Blogs. ( ‘F it’s not green it’s not seen )
Had one of these flying around me in the garden today wasn’tsure what it was, as looked like a cross between a giant fly and a wasp… so glad it didn’t get chance to feast on me as I react badly to mosquito bites – I have about a dozen mossie bites already and I reckon that would cause me some serious discomfort. I’m in Exeter, Devon
Spotted one of these today in Grosmont N Yorkshire. Never seen one before. Thank you for all the information.
Getting a few of these around the garden especially on the lavender in the past week .
We are in Dornoch, Sutherland, the highlands .
One of these horrors today in South West Wales on our sons car. All of us gave it a VERY wide berth. Horse flies have been abundant here this month. Skin So Soft by Avon works very well to keep them from biting, it has a lot of citronella in it. Horsey neighbour tipped me to it, can be used on horses as well as people.
We have had several of these noisy, fast flying flies enter the house in past, hot week. We live on edge of New Forest, feel sorry for all the ponies that must get bitten. Would certainly not like contact with one!
One was on our letter box in West Cumbria this morning. Whizzed past my head when my wife disturbed it.
West cumbria one just hit our window landed shocked and then flies away
Just found one of these in our porch – wondered what on earth it was. Absolutely huge! Thankfully managed to get it our without any of us coming a cropper.
North Wales
I just had one resting on the patio. Really puzzled me a bite but then found this website so puzzle solved.
I live in Bridgend, South Wales. No water around or cattle. Maybe the odd back garden pond, that’s all.
Gill Davies
BRIDGEND
just had one of these land beside me on the garden bench. Initially was a bit concerned as to what it was until I found this website hopefully it’s not a female.
George Gray
Buchlyvie
Found one sunbathing outside on kitchen window-sill 4/5 days ago: pretty sure it was a male. Annoyingly, it had disappeared by the time I returned with a camera to record it. It was a big beggar. Lots of rough grazing – moorland, woodland and boggy ground nearby. A few sheep and cattle on the grazings – but also plenty of deer. Only time I have seen one in 10 years of living on the Isle of Skye.
Went to our woods in West Wales, and 2 of these landed on the hot bonnet of the landie as soon as we stopped. It was like they were attracted to the heat. It was a hot day, and near both coniferous woodland and broad leaf woodland. We had stopped to talk to our neighbour and she was riding her horse, luckily we were so freaked out at how huge they were, we shut the doors and windows and she rode off on her horse. I regularly see small horse flies during June and July down our woodland, but have never seen these before. Horrible looking things!!
I live in blackwood South Wales UK. This was feeding on my dogs poop as she is ill and bleeds after pooping.