Where Are Deer Flies Found: Uncovering Their Habitats

Deer flies are pesky insects that belong to the genus Chrysops, known for their painful bites on humans and animals. If you’ve ever encountered one, you’ll know that they can be a real nuisance. But where exactly can you find these annoying pests?

You are most likely to come across deer flies in damp environments, such as freshwater and saltwater marshes, as well as in moist forest soils and some streams. Their larval phase usually takes place in these moist habitats, which serve as perfect breeding grounds for them. They are commonly found in these areas because the females are in search of hosts to feed on their blood, while the males focus on pollen and nectar, often found on flowers.

Understanding where deer flies are found is crucial to avoiding their painful bites and protecting yourself and your animals from the discomfort they cause. Being aware of their preferred habitats and breeding grounds can help you take the necessary precautions to keep them at bay.

Understanding Deer Flies

Deer flies are a type of insect that belong to the Tabanidae family. They are commonly found in various regions across the globe and can make a significant impact on the experiences of outdoor enthusiasts. In this section, you will gain a better understanding of their characteristics and behaviors.

Deer flies are usually about 1/4 to 1/2 inch long. They are black or brownish in color and their wings often have dark areas. When compared to their relatives, the larger horse flies, deer flies are usually smaller and their eyes typically exhibit spots or patterns which are not found in horse flies.

These flies are attracted to living creatures, such as humans and animals. As a result, they can be found in several environments:

  • Forests and woodlands
  • Wetlands
  • Marshes and swamps
  • Fields and meadows
  • Near bodies of water like lakes, rivers, and streams

One of the primary concerns when dealing with deer flies is their biting behavior. The female deer flies are the ones responsible for inflicting painful bites on humans and animals. They require blood meals for the development of their eggs. In contrast, male deer flies feed on pollen and nectar.

To better understand deer flies and horse flies, let’s examine a comparison table:

Feature Deer Flies Horse Flies
Size 1/4 to 1/2 inch long 3/8 to 1 1/8 inches long
Color Black or brownish Usually gray or blackish
Wings Dark areas on wings Clear wings or uniformly cloudy
Eyes Spots or patterns in the eyes Horizontal stripes in the eyes

Preventing deer fly bites is vital when venturing into their territory. You can use protective clothing, bug spray, and bug nets to help deter them. It’s essential to be aware of their presence in your environment, so you can better enjoy your outdoor activities.

Remember that being knowledgeable about the nature and behavior of deer flies can help you take precautions against their bites. By understanding and respecting their role in the ecosystem, you can coexist with these insects while keeping yourself and your loved ones safe from harm.

Physical Characteristics

Deer flies are quite distinct in their appearance. Here are some key features:

  • Size: Usually ranging from 0.25 to 0.33 inches in length 1.
  • Color: Deer flies are typically black or brownish, with dark areas on their wings 2.
  • Eyes: They have large compound eyes, often with horizontal stripes or spots 3.
  • Antennae: These insects possess short antennae.

In comparison, horse flies have some differences:

  • Size: Horse flies are larger, about 3/8 to 1 1/8 inches long 2.
  • Color: They are usually gray or blackish 2.
  • Eyes: Horse flies also have large compound eyes, but often with horizontal stripes 2.
  • Antennae: Similar to deer flies, horse flies have short antennae.

Both male and female deer flies have some unique characteristics:

  • Male deer flies: They have wider heads and larger eyes, which allow them to easily spot potential mates 4.
  • Female deer flies: Unlike the males, female deer flies require blood meals for egg development and are the ones responsible for biting humans and animals 4.

Let’s summarize the key physical characteristics of deer flies in a comparison table:

Feature Deer Flies Horse Flies
Size 0.25 to 0.33 inches 3/8 to 1 1/8 inches
Color Black or brownish; dark areas on wings Gray or blackish
Eyes Stripes or spots Horizontal stripes
Antennae Short Short

These attributes help differentiate deer flies from other insects and make them easier to identify in their natural habitats, such as freshwater and saltwater marshes, moist forest soils, and areas with moist decomposing wood 1.

Habitats of Deer Flies

Deer flies can be commonly found in wet and aquatic habitats. They are particularly attracted to areas such as marshes, wetlands, and near streams. These environments provide them with ample breeding grounds and food sources.

For example, in the United States, deer flies tend to be more prevalent in the wetter regions, with the exception of Hawaii, where they are not found. They are also absent in colder climates such as Greenland and Iceland.

Their habitats can include both aquatic and terrestrial areas. This is because deer flies lay their eggs close to water sources, but the adult flies often search for food on land.

  • Bullet 1: Wetlands, marshes, and streams are common deer fly habitats.
  • Bullet 2: Deer flies are absent in Hawaii, Greenland, and Iceland.
  • Bullet 3: Aquatic and terrestrial environments are both suitable for deer flies.

In comparison to other fly species, deer flies might be more selective in their habitats since they require wet or damp areas for reproduction. Keep this in mind when you’re exploring the outdoors, and be prepared to encounter deer flies in these types of environments

Life Cycle of a Deer Fly

Deer flies typically go through four main stages in their life cycle: eggs, larvae, pupae, and adults.

Eggs: Deer flies lay eggs on leaves or stems near water sources. In spring, the female deer fly lays clusters of long, shiny black eggs. Such long eggs can hatch within a week, depending on temperature conditions.

Larvae: After hatching, the larvae fall into the water and start feeding on decaying organic matter, small insects, and invertebrates. The larval stage can last for a year or even longer, depending on environmental conditions. During this time, deer fly larvae go through several instar stages and grow larger.

Pupae: Following the larval stage, deer fly larvae crawl out of water and build a protective cocoon in moist soil. Inside the cocoons, deer flies transform into pupae. The pupal stage can last anywhere between one to three weeks, again depending on temperature and humidity.

Adults: After pupating, adult deer flies emerge from the cocoons. They usually appear in late spring or early summer and start searching for a blood meal. Female deer flies feed on blood from various animals, like cattle and humans, while male deer flies mostly feed on plant nectar.

Remember, while deer fly bites can be painful, these insects play a vital role in the ecosystem. So, be careful to take necessary precautions, like using insect repellent and wearing long-sleeved clothing, while venturing into areas where deer flies are commonly found.

Dietary Habits

Deer flies have a unique diet depending on their gender. Let’s dive into the dietary habits of these insects and explore their preferences.

Male deer flies primarily feed on nectar and pollen. As a gardener, you might even spot them hovering around your flowers. Here are a few dietary favorites of male deer flies:

  • Nectar from various flowers
  • Pollen from diverse plants

On the other hand, female deer flies seek out blood meals. This provides them with the essential nutrients required for reproduction. For instance, these blood meals can be taken from various mammals like deer, cattle, or humans.

Their diet may not be as diverse, focusing mainly on:

  • Blood meals from different hosts

Now that we’ve seen the differences in dietary habits between male and female deer flies, it’s essential to keep these aspects in mind when dealing with them in your surroundings.

Interaction with Other Species

Deer flies are found in various environments, and their presence affects different species. Let’s look at how they interact with some of the mentioned entities.

Humans and Mammals: Deer flies are considered a nuisance, especially for humans, cattle, and horses. Their bites can be extremely painful, as these flies feed on the blood of warm-blooded animals. Moreover, they may also transmit diseases to their targets.

Birds: In some cases, deer flies can also be preyed upon by various birds, like killdeer and other insectivorous species that take advantage of the flies as a food source.

  • Predators: Some common predators of deer flies include dragonflies and hornets, which help maintain a balance in the ecosystem by controlling the deer fly population.

To better understand how deer flies interact with these entities, here’s a comparison table for your reference:

Entity Impact Positive/Negative Example Interaction
Humans Painful bites, disease transmission Negative Outdoor activities
Mammals Painful bites, irritants, and diseases Negative Cattle and horses
Birds Serves as a food source Positive Killdeer eating deer flies
Predators Controls deer fly population Positive Dragonflies preying on deer flies

In conclusion, deer flies can have diverse interactions with various species, leading to both negative and positive effects on the ecosystem. By understanding these interactions, we can develop strategies to manage the impact of deer flies and protect the well-being of humans, mammals, and the broader environment.

Ecological Role

Deer flies play an important role in the ecosystem, acting as both predators and prey. Their larvae are aquatic, feeding on small insects and organic matter found in damp, wooded, or wetland environments1. As predators, adult female deer flies feed on the blood of animals, while males primarily feed on pollen and nectar found on plants2. This feeding behavior helps in the movement and pollination of plants in the ecosystem.

During their life cycle, deer flies’ larvae help with the decomposition process of dead plants and organic matter. By breaking down this material, they release essential nutrients into the environment and help recycle carbon dioxide back into the atmosphere3.

In turn, deer flies serve as a food source for various predators such as frogs, toads, spiders, wasps, hornets, dragonflies, and birds like the killdeer1. This makes them an integral part of the food chain that helps to maintain the balance of the ecosystem.

Deer flies are attracted to carbon dioxide that mammals emit through their respiratory systems4. This helps them locate their prey and ensures proper feeding for young deer flies. At the same time, their bites can also transmit diseases, making them a nuisance and a potential health risk to the animals and humans they feed upon. To summarize, here are some key aspects of deer flies’ ecological role:

  • Act as predators feeding on blood of animals and organic matter in water
  • Serve as prey for various other animals in the ecosystem
  • Contribute to plant pollination and decomposition of organic matter
  • Influence the movement of certain animal species due to their bites and possible disease transmission

Human Impact

Deer flies are notorious for their painful bites. When one bites you, it can cause significant pain. Their bites cut into the skin, which allows them to feed on your blood.

You might experience an allergic reaction to these bites. Some common symptoms include:

  • Hives
  • Wheezing
  • Painful and swollen wounds

Deer flies are found in various environments, mostly in the countryside near water sources. They are attracted to humans and animals, making it essential to take precautions when spending time outdoors during their active season.

Here’s a short comparison of deer fly bites versus other common insects:

Insect Pain Level Allergic Reaction Bite Description
Deer Fly High Yes Painful, bleeding
Mosquito Low Yes Itchy, red bump
Horse Fly High Yes Painful, large swelling

To minimize your chances of encountering deer flies and their painful bites, avoid their natural habitats, especially during peak seasons, and use insect repellent on your clothes and exposed skin areas. Additionally, wearing light-colored clothing can help deter these pests, as they are attracted to darker colors.

Deer Fly Control

Deer flies can be a nuisance, but there are several methods for controlling them. To protect yourself, consider using a repellent. Some repellents are specifically designed for deer flies and can be applied to your skin or clothing. Here are some repellent options:

  • DEET-based repellents
  • Picaridin-based repellents
  • Natural oil repellents (e.g., lemon eucalyptus oil)

When it comes to deer fly control around your property, insecticides can be an effective solution. However, keep in mind that they may also affect non-target insects. It’s best to use insecticides sparingly and follow the directions carefully.

Another control method is using traps to catch deer flies. Some examples include:

  • Sticky traps (e.g., Tanglefoot-coated objects)
  • Commercial deer fly traps
  • DIY bottle traps with bait

Traps can be strategically placed near areas where deer flies are commonly found. Be sure to check and replace traps regularly to maintain effectiveness.

In summary, controlling deer flies involves a combination of repellents, insecticides, and traps. By using these techniques, you can minimize your encounters with these pesky insects and enjoy your outdoor activities with peace of mind.

Diseases Spread by Deer Flies

Deer flies, belonging to the Chrysops genus, are notorious for spreading various diseases through their bites. Let’s take a look at some notable diseases that deer flies transmit.

Tularemia, also known as deer fly fever or rabbit fever, is a bacterial infection caused by the Francisella tularensis bacteria. This can be transmitted to humans and animals when deer flies bite and inject their saliva, which contains the bacteria, into their host. Symptoms of tularemia include fever, chills, and swollen lymph nodes.

Another disease transmitted by deer flies is anthrax. Although less common, deer flies can carry the Bacillus anthracis bacteria, which causes anthrax. The bacteria can enter the body through deer fly bites or contact with infected animals. Anthrax can cause skin sores, fever, and muscle aches.

In addition to transmitting diseases, deer fly bites can be painful due to their unique maxillae. These mouthparts are like tiny knives that slice through the skin, allowing the fly to feed on blood. To minimize the risk of deer fly bites and reduce the chance of contracting diseases from them, you can take several preventive measures:

  • Wear long-sleeved clothing and pants
  • Use insect repellents containing DEET
  • Avoid outdoor activities in areas with high deer fly populations, especially during their peak season

Remember to always be cautious and take precautions when venturing into areas with deer flies to protect yourself from these potentially disease-spreading insects.

Genera and Species

Deer flies are found in wet and damp environments, and belong to the genus Chrysops. They are smaller, usually about 1/4 to 1/2 inch long, and come in black or brownish colors with dark areas on their wings 1. Their eyes usually have spots 1.

The larval stage of deer flies is aquatic, with them feeding on small insects and pupating in the mud at the edge of the water 2. Their natural predators include frogs, toads, spiders, wasps and hornets, dragonflies, and birds such as killdeer 2.

In comparison, horse flies are larger and belong to the genus Tabanus. They are around 3/8 to 1 1/8 inches long, and have a gray or blackish color 1. Horse fly wings generally lack dark areas, but some species do have entirely dark wings 1. Their eyes often display horizontal stripes 1.

Deer flies and horse flies are known for their painful bites which females inflict as they require blood to reproduce 3. While these flies are found worldwide, specific species have varying distributions depending on their preferred habitats 4. For instance, Indiana alone has about 45 species of horse flies and 30 species of deer flies 5.

Key characteristics to identify deer and horse flies include:

  • Size: Horse flies are larger than deer flies.
  • Wings: Horse flies usually lack dark areas on their wings, while deer flies have dark areas.
  • Eyes: Horse flies have horizontally striped eyes, while deer flies have spotted eyes.

Remember to protect yourself from these biting flies when outdoors, especially in damp or wet forested areas.

Other Interesting Facts

Did you know that deer flies are usually found around swimming pools? They’re attracted to the water, especially during the warmer months of May through September. Deer flies can be quite a nuisance, as they like to attack humans and other animals. They’re especially bothersome when you’re trying to enjoy a relaxing day by the pool.

Deer flies typically have a two-month life cycle. They prefer warmer temperatures. Some important factors about deer flies include:

  • Active during May to September
  • Found around swimming pools
  • Prefer warm temperatures
  • Two-month life cycle

While dealing with deer flies can be bothersome, it’s important to remember that they’re part of the natural ecosystem. Being aware of their presence and taking the necessary precautions can help you enjoy your outdoor activities during the peak months of their activity.

Footnotes

  1. https://extension.entm.purdue.edu/publichealth/insects/tabanid.html 2 3 4 5 6 7 8 9

  2. https://extension.umd.edu/resource/horse-and-deer-flies 2 3 4 5 6 7

  3. https://mdc.mo.gov/discover-nature/field-guide/horse-deer-flies 2 3

  4. https://entnemdept.ufl.edu/creatures/livestock/deer_fly.htm 2 3 4

  5. Horse and Deer Flies | Public Health and Medical Entomology | Purdue

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Yellow Fly of the Dismal Swamp

 

Subject:  Please ID this bug
Geographic location of the bug:  Saint Johns Florida
Date: 05/31/2018
Time: 05:30 PM EDT
Your letter to the bugman:  Inhave a pesky, biting insect that looks like a fly, about the size of one and is as quick as one.  The only thing is that it bites/stings.  It has a touch of red on it and is a little larger than one.  It’s very aggressive and leaves a big bump with it’s bite/sting.
How you want your letter signed:  Quckly

Yellow Fly of the Dismal Swamp

Dear Quckly,
While we empathize with your situation, we are nonetheless quite amused to learn that the common name of the Horse Fly,
Diachlorus ferrugatus, that is troubling you is, according to BugGuide, the Yellow Fly of the Dismal Swamp.  According to Featured Creatures:  “The female yellow fly is one of the most serious biting fly pests wherever it occurs (males do not bite). It attacks man vigorously, and the bites are painful, often causing large and itchy swellings. Although it attacks throughout the day, it is most active during the late afternoon and on cloudy days. It is especially common near large bodies of water, but tends to remain in or near forests. It is one of the few tabanids that attacks indoors. All exposed parts of the victim’s body may be attacked, and since the flight is rather quiet, a person is not aware of the flies until the sharp pain of the bite is felt. Domestic animals, including dogs, are attacked readily, although the fly’s preference for shade makes it less of a pest to cattle and horses in open pastures. Flies are on the wing in Florida from March to November, although the peak season is April through June.”  According to BugGuide:  “one of the first horse fly species described from North America.” 

Yellow Fly of the Dismal Swamp

Letter 2 – Possibly Moth Eggs on Deer Fence

 

Subject: Eggs on deer netting
Location: Northeastern Massachusetts
September 18, 2013 2:04 pm
Many groups of eggs have been deposited on my deer netting this year. I’d like to know what kind of insect they are. For size reference, the netting is one-half inch per square.
I live in northeastern Massachusetts. Groups of eggs were deposited throughout this summer. The photo shows one group, but there are about a hundred groups over 30 feet of netting. The colors are various shades of beige to medium brown. Several groups have either hatched or been eaten. I have been using using deer netting for 4 years, but this is the first year for eggs.
Thanks!
Signature: Pam

Eggs on Fence
Eggs on Fence

Hi Pam,
We can’t say for certain what type of eggs these are, but our initial guess is Moth Eggs of some type.  Perhaps one of our readers will have an idea.

Possibly Moth Eggs
Possibly Moth Eggs

More information:  The deer netting with the egg clusters is in full sun.  The netting that is in partial shade has no eggs.  Thanks for your help!

Letter 3 – Hippo Fly from South Africa

 

Subject: Massive black fly with distinct yellow spots
Location: Melkbosstrand, Cape Town, Western Cape, South Africa
January 5, 2014 4:25 am
This is the first time we have since this massive ‘fly’ – we took photos of him and thought it would be easy to identify him using our insect book, as he is so distinct, but it appears we are battling – real novices! Do you possibly know what type of fly it is? May not even be a fly…
Signature: Emma Theron

Male Horse Fly
Male Hippo Fly

Hi Emma,
Before we start our research, we will begin by telling you that the common family name for this fly in North America is Horse Fly, but in Australia, the same family is referred to as the March Flies, and that common name refers to a totally different family in North America.  We are going to use the scientific taxonomic name, which is Tabanidae.  It will be easier to begin our search of South African members that way.  We can also tell you that because of the close eye placement, this is a male Horse Fly and it is only the females that suck the blood from warm blooded mammals.  Horse Flies generally feed on livestock, but they can and do bite humans and the bite is somewhat painful.  Again, this is a male and only the females bite.
Continued research led us a matching photo and a very interesting answer. There was an identification request posted to ISpot and David Notton wrote in and identified it as a Hippo fly (
Tabanus biguttatus).  We found another image on Zandvlei Trust confirming the name Hippo Fly with the information:  “Adults attack large mammals such as hippos as blood suckers. Their larva feed on insect larva and tadpoles in mud pans.”  On South African Photographs, a photo of a female fly (space between the eyes) is identified as a Hippo Fly, Tabanus biguttatus, but the spotted abdomen is not visible.  Instead, the thoracic region is golden, leading us to believe there is pronounced sexual dimorphism in this species beyond the difference in the eyes which is characteristic of the entire family.  South African PHotographs indicates:  “These flies are huge – must be at least an inch in body length if not more. They attack large animals such as cattle and hippo’s driving them to spend the night underwater to avoid being bitten.” A similarly marked female is also pictured and identified on ISpotPHotos of both an identified female and unidentified male are pictured on the slide show of flies on Natures World of Wonder South Africa.  We would love to locate some reference that pictures both the male and female and discusses the distinctive differences between the coloration and markings of the sexes.

Thanks so much Daniel for the feedback and the good explanations and cross-references, I really appreciate it!
Kind Regards,
Emma

Letter 4 – Deer Fly Bites Butterfly Fancier with Karner Blue

 

Subject:  Beautiful biting fly (with bonus Karner Blue)
Geographic location of the bug:  Albany Pine Bush, Albany, NY
Date: 07/07/2020
Time: 12:33 AM EDT
Your letter to the bugman:  Dear Bugman,
Susan B. here with another dispatch from the Albany Pine Bush! I was having a nice raspberry-picking expedition along the trail when a rather beautiful fly came along and landed on my finger. I was so enchanted by its incredible eyes that I failed to notice it had stabbed its proboscis right into my flesh! I shooed it away, and I still have a sore spot where it bit me. Any idea who this rude little creature was?
Astute viewers will notice that while I was dealing with the fly situation, I was also providing transport to another, equally beautiful but much more polite hitchhiker: a Karner Blue that had come along and landed on my finger a few minutes earlier. I’m pleased to say I managed to both photograph and shoo the fly without disturbing my other passenger, who stuck around, lapping up my sweat, for a good quarter mile of trail.
How you want your letter signed:  Susan B.

Deer Fly

Dear Susan,
Thanks for your highly entertaining query.  You have been bitten by a Deer Fly.  According to BugGuide:  “Adults feed on plant nectar; females on vertebrate blood; larvae carnivorous and detritus feeders.”  You described their “incredible eyes”, and this BugGuide image beautifully captures the details of the eyes of a Deer Fly. Blues are one of the groups of butterflies that frequently have “puddle parties” on damp earth, a behavior beautifully described by Vladimir Nabakov in his fiction, and scientists believe they derive important minerals from this behavior.  We suspect your salty perspiration fulfilled your Karner Blue‘s need for moisture and minerals.

Karner Blue

Reader Emails

Over the years, our website, whatsthatbug.com has received hundreds of letters and some interesting images asking us about these insects. Scroll down to have a look at some of them.

Letter 1 – Yellow Fly of the Dismal Swamp

 

Subject:  Please ID this bug
Geographic location of the bug:  Saint Johns Florida
Date: 05/31/2018
Time: 05:30 PM EDT
Your letter to the bugman:  Inhave a pesky, biting insect that looks like a fly, about the size of one and is as quick as one.  The only thing is that it bites/stings.  It has a touch of red on it and is a little larger than one.  It’s very aggressive and leaves a big bump with it’s bite/sting.
How you want your letter signed:  Quckly

Yellow Fly of the Dismal Swamp

Dear Quckly,
While we empathize with your situation, we are nonetheless quite amused to learn that the common name of the Horse Fly,
Diachlorus ferrugatus, that is troubling you is, according to BugGuide, the Yellow Fly of the Dismal Swamp.  According to Featured Creatures:  “The female yellow fly is one of the most serious biting fly pests wherever it occurs (males do not bite). It attacks man vigorously, and the bites are painful, often causing large and itchy swellings. Although it attacks throughout the day, it is most active during the late afternoon and on cloudy days. It is especially common near large bodies of water, but tends to remain in or near forests. It is one of the few tabanids that attacks indoors. All exposed parts of the victim’s body may be attacked, and since the flight is rather quiet, a person is not aware of the flies until the sharp pain of the bite is felt. Domestic animals, including dogs, are attacked readily, although the fly’s preference for shade makes it less of a pest to cattle and horses in open pastures. Flies are on the wing in Florida from March to November, although the peak season is April through June.”  According to BugGuide:  “one of the first horse fly species described from North America.” 

Yellow Fly of the Dismal Swamp

Letter 2 – Possibly Moth Eggs on Deer Fence

 

Subject: Eggs on deer netting
Location: Northeastern Massachusetts
September 18, 2013 2:04 pm
Many groups of eggs have been deposited on my deer netting this year. I’d like to know what kind of insect they are. For size reference, the netting is one-half inch per square.
I live in northeastern Massachusetts. Groups of eggs were deposited throughout this summer. The photo shows one group, but there are about a hundred groups over 30 feet of netting. The colors are various shades of beige to medium brown. Several groups have either hatched or been eaten. I have been using using deer netting for 4 years, but this is the first year for eggs.
Thanks!
Signature: Pam

Eggs on Fence
Eggs on Fence

Hi Pam,
We can’t say for certain what type of eggs these are, but our initial guess is Moth Eggs of some type.  Perhaps one of our readers will have an idea.

Possibly Moth Eggs
Possibly Moth Eggs

More information:  The deer netting with the egg clusters is in full sun.  The netting that is in partial shade has no eggs.  Thanks for your help!

Letter 3 – Hippo Fly from South Africa

 

Subject: Massive black fly with distinct yellow spots
Location: Melkbosstrand, Cape Town, Western Cape, South Africa
January 5, 2014 4:25 am
This is the first time we have since this massive ‘fly’ – we took photos of him and thought it would be easy to identify him using our insect book, as he is so distinct, but it appears we are battling – real novices! Do you possibly know what type of fly it is? May not even be a fly…
Signature: Emma Theron

Male Horse Fly
Male Hippo Fly

Hi Emma,
Before we start our research, we will begin by telling you that the common family name for this fly in North America is Horse Fly, but in Australia, the same family is referred to as the March Flies, and that common name refers to a totally different family in North America.  We are going to use the scientific taxonomic name, which is Tabanidae.  It will be easier to begin our search of South African members that way.  We can also tell you that because of the close eye placement, this is a male Horse Fly and it is only the females that suck the blood from warm blooded mammals.  Horse Flies generally feed on livestock, but they can and do bite humans and the bite is somewhat painful.  Again, this is a male and only the females bite.
Continued research led us a matching photo and a very interesting answer. There was an identification request posted to ISpot and David Notton wrote in and identified it as a Hippo fly (
Tabanus biguttatus).  We found another image on Zandvlei Trust confirming the name Hippo Fly with the information:  “Adults attack large mammals such as hippos as blood suckers. Their larva feed on insect larva and tadpoles in mud pans.”  On South African Photographs, a photo of a female fly (space between the eyes) is identified as a Hippo Fly, Tabanus biguttatus, but the spotted abdomen is not visible.  Instead, the thoracic region is golden, leading us to believe there is pronounced sexual dimorphism in this species beyond the difference in the eyes which is characteristic of the entire family.  South African PHotographs indicates:  “These flies are huge – must be at least an inch in body length if not more. They attack large animals such as cattle and hippo’s driving them to spend the night underwater to avoid being bitten.” A similarly marked female is also pictured and identified on ISpotPHotos of both an identified female and unidentified male are pictured on the slide show of flies on Natures World of Wonder South Africa.  We would love to locate some reference that pictures both the male and female and discusses the distinctive differences between the coloration and markings of the sexes.

Thanks so much Daniel for the feedback and the good explanations and cross-references, I really appreciate it!
Kind Regards,
Emma

Letter 4 – Deer Fly Bites Butterfly Fancier with Karner Blue

 

Subject:  Beautiful biting fly (with bonus Karner Blue)
Geographic location of the bug:  Albany Pine Bush, Albany, NY
Date: 07/07/2020
Time: 12:33 AM EDT
Your letter to the bugman:  Dear Bugman,
Susan B. here with another dispatch from the Albany Pine Bush! I was having a nice raspberry-picking expedition along the trail when a rather beautiful fly came along and landed on my finger. I was so enchanted by its incredible eyes that I failed to notice it had stabbed its proboscis right into my flesh! I shooed it away, and I still have a sore spot where it bit me. Any idea who this rude little creature was?
Astute viewers will notice that while I was dealing with the fly situation, I was also providing transport to another, equally beautiful but much more polite hitchhiker: a Karner Blue that had come along and landed on my finger a few minutes earlier. I’m pleased to say I managed to both photograph and shoo the fly without disturbing my other passenger, who stuck around, lapping up my sweat, for a good quarter mile of trail.
How you want your letter signed:  Susan B.

Deer Fly

Dear Susan,
Thanks for your highly entertaining query.  You have been bitten by a Deer Fly.  According to BugGuide:  “Adults feed on plant nectar; females on vertebrate blood; larvae carnivorous and detritus feeders.”  You described their “incredible eyes”, and this BugGuide image beautifully captures the details of the eyes of a Deer Fly. Blues are one of the groups of butterflies that frequently have “puddle parties” on damp earth, a behavior beautifully described by Vladimir Nabakov in his fiction, and scientists believe they derive important minerals from this behavior.  We suspect your salty perspiration fulfilled your Karner Blue‘s need for moisture and minerals.

Karner Blue

Authors

  • Daniel Marlos

    Bugman aka Daniel Marlos has been identifying bugs since 1999. whatsthatbug.com is his passion project and it has helped millions of readers identify the bug that has been bugging them for over two decades. You can reach out to him through our Contact Page.

  • Piyushi Dhir

    Piyushi is a nature lover, blogger and traveler at heart. She lives in beautiful Canada with her family. Piyushi is an animal lover and loves to write about all creatures.

11 thoughts on “Where Are Deer Flies Found: Uncovering Their Habitats”

  1. I found a cluster of very similar-looking eggs on a milkweed leaf last week here in northern-ish Illinois, and I *think* I may have ID’ed mine as Pearly Underwing or Variegated Cutworm eggs (Peridroma saucia). What do you think? -Dori

    Reply
  2. I am also in northeast Massachusetts and have had the exact same issue this year. I found some caterpillars in the soil earlier in the year, so Dori’s guess in the above comment seems sensible to me.

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  3. We just got this big ugly fly that we have never seen before. On this site we saw that it was the Hippo fly. We are in Uitenhage, Eastern Cape.

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  4. Hi! (2016)
    I am up in Northern Ontario near Lake Huron and have similar egg clusters on deck netting!
    No idea… Guess it will be a surprise and hopefully a good one.
    Cindy

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  5. Hi! (2016)
    I am up in Northern Ontario near Lake Huron and have similar egg clusters on deck netting!
    No idea… Guess it will be a surprise and hopefully a good one.
    Cindy

    Reply
  6. I have a similar cluster of whitish eggs on monofilament fishing line, used to deter deer, Salish Sea area of Olympic Peninsula, WA.

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  7. Has one found out what they are?? I have them on my fence as well. Although, they only seem to go on the black fence not on the metal one.

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  8. I have the exact same thing in Eugene/Springfield area of Oregon. I saw some of the hatched larvae. The were some kind of gray inchworm or looper. I have no idea what species.

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  9. We have them all over our deer netting here on Vancouver Island in Canada. I’m pretty sure they can’t be good – have heard that they are army worms. Rather than trying to wash them off, we have been spray painting the lines of them as they turn up. Works just fine and they don’t hatch.

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