What Attracts Horse Flies: Top Lures & Prevention Tips

Horse flies are notorious for their painful bites, and they can be a serious nuisance to humans, livestock, and other animals. Understanding what attracts these pesky insects can help you avoid unwanted encounters and minimize their impact on your outdoor activities. One key factor that draws horse flies to their targets is the detection of … Read more

What Do Horse Flies Eat: Unraveling Their Diet Secrets

Horse flies are known for their painful bites, but have you ever wondered what they eat? These bloodsucking insects can be a nuisance to humans, horses, and cattle alike. Understanding their diet can help us better prepare for encounters with these pesky pests. Adult horse flies primarily feed on the blood of mammals, particularly large … Read more

Black Fly vs Horse Fly: Uncovering the Key Differences and Impacts

Black flies and horse flies are both bothersome insects that can disrupt outdoor activities and even cause painful bites. These two types of flies have different characteristics and habitats, which can help us understand their behavior and find ways to prevent or manage their presence. Black flies typically develop in flowing water, often found in … Read more

Black Horse Fly: All You Need to Know in a Quick Guide

Black horse flies are a type of large, robust biting fly commonly found near bodies of water. These creatures are known for causing irritation and discomfort to both humans and animals alike. With their considerable size and pesky nature, it’s essential to understand how to identify and manage their presence effectively. One key characteristic of … Read more

Deer Fly vs Horse Fly: Unraveling the Key Differences

Deer flies and horse flies belong to the Tabanidae family and are both known for their annoying and painful bites. These bloodsucking insects can be quite bothersome, especially to cattle, horses, and humans. Understanding the differences between them can help you better identify and manage these pests.

Deer flies are typically smaller, measuring between 10 to 13 mm long, with greenish-yellow thoraxes featuring dark stripes. Their wings appear tinted smokey gray-brown or showcase dark patterns. On the other hand, horse flies are larger, ranging from 14 to 19 mm in length, and possess clear wings and grayish-brown thoraxes.

Aside from their physical distinctions, each species’ behavior and habitat can also vary.

Deer Fly and Horse Fly: A Comparison

Appearance

Deer flies and horse flies are bloodsucking insects with a few differences in appearance. Let’s examine their distinct characteristics:

  • Deer flies:

    • Smaller in size, typically around 6-10 mm1
    • Dark bands across the wings2
    • Brightly colored compound eyes2
  • Horse flies:

    • Larger, ranging from 20-25 mm1
    • Clear or solidly colored wings2
    • Vibrant compound eyes2

Habitat

Both deer flies and horse flies can be found in environments with nearby water sources due to their aquatic larval stages3. However, deer flies are more often encountered in wooded areas, while horse flies prefer open areas such as pastures and meadows4.

Distribution

Deer flies (Chrysops) and horse flies (Tabanus) can be found across most regions of the United States, although they’re more prevalent in warmer climates5. Notable differences in distribution include:

  • Deer flies: Higher concentrations in the southeastern US5
  • Horse flies: Widespread throughout the US but less common in arid regions5

Comparison Table

Feature Deer Fly Horse Fly
Size 6-10 mm 20-25 mm
Wing Appearance Dark bands Clear or solid
Eye Color Brightly colored Vibrant
Preferred Habitat Wooded areas Open areas
Distribution Southeastern US Widespread in US

Life Cycle and Reproduction

Eggs

  • Both deer flies and horse flies lay their eggs on vegetation near wetlands or aquatic habitats.
  • Females typically lay eggs in specific locations, for example on vegetation overhanging water3.

Larvae

  • The larvae of both flies are generally white, brownish, or greenish in color1.
  • Deer fly larvae are usually smaller than horse fly larvae1.
  • Both types of larvae are spindle-shaped and taper to a point at both ends1.
  • Larval stage feeding habits:
    • Deer fly larvae are predaceous and inhabit wet or semi-aquatic environments4.
    • Horse fly larvae are predaceous and can be found in wet areas or terrestrial environments5.

Pupa

  • Winter is spent in the larval stage, with pupation occurring in spring3.
  • The pupal stage of both flies is spent in the same aquatic or wetland habitat as the larvae3.

Adult

  • Adult emergence happens during late spring and summer3.
  • Deer fly adults are 6-10 mm long and yellow to brown in color with patterned wings5.
  • Horse flies range in size from 3/4 to 1-1/4 inches long, with clear or solidly colored wings and brightly colored eyes2.

Comparison Table:

Aspect Deer Fly Horse Fly
Size 6-10 mm long5 3/4 to 1-1/4 inches long2
Wing Patterns Patterned5 Clear or solidly colored2
Larval Habitat Wet or semi-aquatic environments4 Wet areas or terrestrial environments5
Adult Habitat Wetlands, aquatic1 Wetlands, aquatic1

Feeding and Biting Habits

Adult Feeding Habits

Both horse flies and deer flies exhibit different feeding habits among their male and female counterparts. As adults, male horse flies and deer flies primarily feed on nectar, while their female counterparts need blood meals for egg production.

Female horse flies and deer flies are attracted to several factors from potential hosts, including carbon dioxide, body heat, and movement. For example, female deer flies tend to bite humans while they are outdoors near wooded areas.

Blood-Sucking Bites

The bites from both horse flies and deer flies can be quite painful, as their mouthparts cut the skin rather than pierce it. This blood-sucking habit can lead to the spread of various diseases and infections.

The bite differences can be seen below:

Feature Horse Fly Bite Deer Fly Bite
Pain Level More painful Less painful
Bite location Exposed skin Exposed skin
Mouthparts Scissor-like Scissor-like

Horse Flies

  • Larger size (14 to 19 mm long)
  • Clear wings
  • Grayish-brown thorax
  • More aggressive bites
  • Found near livestock, such as in barns

Deer Flies

  • Smaller size (10 to 13 mm long)
  • Tinted or patterned wings
  • Greenish-yellow thorax with dark stripes
  • Less aggressive bites
  • Found in wooded and marshy areas

Some ways to protect yourself and animals from these bites include using essential oils, wearing protective clothing, and avoiding areas where these flies are more prevalent. Horse and deer flies are daytime biters, so turning horses out at night instead of the day can help reduce biting. Providing shelter or canopy trees far from wooded edges can also protect horses from bites.

Health Impacts and Control Methods

Diseases Transmitted

Deer flies and horse flies are blood-sucking insects that can be serious pests for livestock and humans. They can transmit various diseases in the process, some of which include:

  • Anaplasmosis: A bacterial infection that affects mostly cattle, but can also impact sheep and goats.
  • Tularemia: A bacterial disease affecting humans, known as “rabbit fever.”
  • Equine infectious anemia: A viral disease that affects horses.
  • Hog cholera: A highly contagious viral disease in pigs.
  • Anthrax: A bacterial infection that can infect livestock and humans.
  • Filariasis: A parasitic infection transmitted by deer flies that can cause health problems in humans.

Prevention and Repellents

Preventing deer fly and horse fly bites is essential in controlling the spread of diseases. Some effective measures include:

  • Regularly inspect and maintain fences and screens to minimize access for flies.

  • Use approved pesticides, like permethrin-based sprays, to control flies in livestock areas.

  • Apply repellents to livestock and humans when in infested areas.

    Examples of deer fly and horse fly repellents:

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

Comparison Table

Feature Deer Fly Horse Fly
Size 6-10 mm long 14-19 mm long
Color Yellow to brown Grayish-brown
Wings Patterned Clear

As members of the family Tabanidae, deer flies and horse flies share some common characteristics. Tabanid flies are robust, capable of biting, and can transmit diseases to both livestock and humans. The health impacts of these pests can be severe if not controlled properly through prevention and the use of repellents.

Interesting Facts and Behaviors

Predators and Prey

Deer flies and horse flies are known as bloodsucking pests that can cause discomfort to humans and animals. They can be active in various environments, such as forests and wetland environments. Adult female deer flies and horse flies feed on the blood of mammals, while adult males feed mainly on pollen and nectar.

Some common predators of these flies include birds and other insects. Interestingly, some people utilize fly traps outdoors to control their numbers around their property.

Mating and Attraction

The mating habits of deer flies and horse flies are quite fascinating. Males and females come together in a specific location, usually near vegetation, to mate.

Deer Flies Horse Flies
Smaller in size (10 to 13 mm long) Larger in size (14 to 19 mm long)
Greenish-yellow thorax Grayish-brown thorax
Smokey gray-brown wings Clear wings

In order to attract mates, male flies often rely on visual cues. Once the female is attracted, the pair will engage in a flight dance before mating. After mating, female flies will search for a suitable host to feed on in order to obtain the nutrients necessary for egg development.

  • Both flies undergo metamorphosis, passing through egg, larva, pupa, and adult stages.
  • Can be found in outdoor and wetland environments.

While there are many similarities between deer flies and horse flies, they do have some different features that set them apart. By observing their distinct sizes, thorax colors, and wing patterns, it’s easier to identify which is which.

It’s important to protect yourself and your animals from these bloodsucking pests by using protective clothing, repellents, and fly traps when necessary.

Footnotes

  1. Texas A&M University 2 3 4 5 6 7

  2. University of Kentucky – Entomology 2 3 4 5 6 7

  3. NC State Extension Publications 2 3 4 5

  4. Wisconsin Horticulture 2 3

  5. UF/IFAS 2 3 4 5 6 7 8

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 – Horse Fly

 

Albino Fly?
August 16, 2009
This bug was filmed in keystone heights florida. What is it? It looks like a fly, but not. I did save it after it died and still have it.
I couldn’t get a decent photo of it, but here is a movie
http://hartmanndesign.net/whitebug.mov
Clair
Northern Florida

Horse Fly:  Chlorotabanus crepuscularis
Horse Fly: Chlorotabanus crepuscularis

Hi Clair,
This is Chlorotabanus crepuscularis, a species of Horse Fly.  According to BugGuide:  “Identification  Body pale green, eyes and thorax yellowish green. The only green tabanid in NA.  Range  An eastern species occurring south of a line from Delaware to southern Texas.  Habitat  Larvae predaceous, usually in soil at edge of water and in floating vegetation, occasionally in forest soil.  Adults in vicinity of larval habitats  Season  In Florida, flying from mid-March to mid-September with peak activity from May to mid-July.  Food  Females feed on mammalian blood  Remarks  As with all the blood-feeding tabanids, the females are responsive to Carbon Dioxide. I caught over 500 females in one night with a trap baited with dry ice in coastal South Carolina. Will also come to lights at night.
Regarded as a pest species in Florida

Letter 2 – Horse Fly

 

Huge Fly
July 5, 2010
This really, really big fly was sitting on a leaf and sat still while I got a close shot (I was taking pics of a butterfly when I saw him). We live in Delaware and I have seen these large flies around and they scare the bjesus outta me. I have searched with no success….any clue?
Janis
Kent County, Delaware

Horse Fly

Hi Janis,
This is a Horse Fly, and though Horse Flies are known to bite animals and humans, you have nothing to fear from this individual.  Only female Horse Flies are blood suckers.  The male Horse Flies do not bite.  The males can be identified by the structure of the eyes.  The two compound eyes of the male Horse Flies have no space between them while the eyes of the females have a separation.  We believe, based on photos posted to BugGuide, that this might be
Tabanus abdominalis, though an expert in Horse Flies might be required to give a conclusive species identification.

Letter 3 – Horse Fly

 

Large fly with horn-like antennae(?)
Location:  New Boston, MI
August 15, 2010 10:19 pm
Found this guy in the first half of August in southeast Michigan. It landed on my car in a rural area, with fields, woodlands, marshlands, and a small river all nearby. It was fairly large, about an inch long or more. I spent years of my childhood exploring the area and have never seen anything like it.
Randall Mosier

Horse Fly

Hi Randall,
We believe we have properly identified your Horse Fly as
Tabanus sackeni based on images posted to BugGuide.  It appears that your specimen is a female because of the space between her eyes.  Like Mosquitoes, Female Horse Flies bite while males do not.

Horse Fly

Letter 4 – Horse Fly

 

Hitch-hiking Horse Fly
Location:  North Middle Tennessee
August 16, 2010 8:22 pm
While driving down a country road looking for insects to photograph this one found me. It landed by the passenger side window. My wife saw it first and said, ”I don’t know what the heck that is.” I knew it was a horse fly but that was about all. I just now looked at the website to try and ID it. The very first horse fly (from yesterday) looks like a match. It appears this is a ”Tabanus sackeni” I wonder if they have a habit of hitching rides. Randall from Mi said his landed on the car as well. Thanks and have a great day.
Richard

Horse Fly

Hi Richard,
Our first thought upon looking at your images was that Randall sent more photos because your images are so similar to his.  We agree that this is another female
Tabanus sackeni, though we always allow for expert corrections to our amateur attempts.  You pose an interesting question.  We doubt that Horse Flies have evolved to the point that they are using Phoresy to get around.  Phoresy is the act of one creature hitching a ride on another creature.  We suspect it is more a matter of being attracted to the color of the car, or the reflectance, or something that we just don’t understand, but whatever the reason, it might make a nice study for a research paper.

Horse Fly

Read more

Do Horse Flies Bite? Discover the Truth About These Pesky Insects

Horse flies and deer flies are a common nuisance for both humans and animals, particularly during the warmer months. These insects are known for their persistent and painful bites, which can affect animals like horses, cattle, and deer as well as people. Female horse flies and deer flies are the ones responsible for inflicting these … Read more