Currently viewing the category: "Horse Flies and Deer Flies"
What's That Bug? does not endorse extermination

Subject: Unknown Fly
Location: Houston
May 11, 2016 9:22 am
Can you id this fly? About size of blow fly. Found outside warehouse, near septic tank.
Signature: Richard

American Horse Fly

American Horse Fly

Dear Richard,
We quickly identified your female Horse Fly on BugGuide as
Tabanus americanus, but we cannot fathom why it was not given the common name American Horse Fly based on its scientific species name.  According to BugGuide:  “Planet Earth’s largest tabanid.”  That would make it a pretty large Horse Fly.  Only female Horse Flies bite and feed on blood, and when there is no livestock available, they will bite humans.  The Encyclopedia of Life does refer to this as the American Horse Fly.

What's That Bug? does not endorse extermination

Subject: What is this bug?
Location: Valley
May 8, 2016 5:51 pm
Hello i live in california bakersfield and saw this bug and couldnt find out what it is can you identify it?
Signature: Caleb

Male Western Horse Fly

Male Western Horse Fly

Dear Caleb,
This is a male Western Horse Fly,
Tabanus punctifer, a species with pronounced sexual dimorphism, meaning the males and females can be mistaken for different species.  Here is a matching image from BugGuide.  The males have larger eyes with no spacing between them.  Only female Horse Flies feed on blood.

What's That Bug? does not endorse extermination

Subject: Biting fly
Location: Northern Uruguay
March 30, 2016 11:30 am
Hello. These are driving me crazy. and I finally got some pictures of them. The are pretty aggressive, circle around, then land on a leg and start biting. They produce painful swollen welts. They have been around from early summer through the fall. They appear to be territorial, yet they “hunt me” in pairs.
Any identification would be appreciated.
Thanks
Signature: Louis

Deer Fly

Deer Fly

Deer Fly

Deer Fly

Dear Louis,
Some of our more sensitive readers might want us to tag your submission as Unnecessary Carnage, but in our minds, blood suckers are fair game when it comes to battling with insects.  Interestingly only female Mosquitoes and Horse Flies flies suck blood, and the same holds for your Deer Flies in the Subfamily Chrysopsinae, relatives of Horse Flies in the family Tabanidae, like your individuals.  Males and females both feed on nectar, but females need blood before they are able to produce eggs.  Were you painting?  Was it oil or resin based paint?  We understand that some Beetles are attracted to fumes from paints and other solvents, but we don’t know if some Flies are similarly attracted.  You can get more information on Deer Flies on the Orkin site.

Four Deer Flies

Four Deer Flies

What's That Bug? does not endorse extermination

Subject: What’s this biting fly?
Location: Orlando
March 18, 2016 9:37 am
Can you identify this biting fly? It has a slightly painful bite. It’s similar to a deer fly but black-bodied instead of yellow. Orange spot on head. Orlando in March. Lots of them bothering us.
Signature: Anemic in FL

Deer Fly

Deer Fly

Dear Anemic in FL,
We believe we have correctly identified your biter from Florida as a Deer Fly,
Chrysops divisus, based on this BugGuide image, also from Florida and also credited with biting.  According to BugGuide:  “Known only from Florida and Georgia. B & H show distribution in extreme SE Georgia (4 counties)” and “in Florida flies from late February to late July in Georgia April – June.”  BugGuide also notes:  “Regarded as a serious pest of man in Florida.”

What's That Bug? does not endorse extermination

Subject: Huge fly out cicada?
Location: NW Iowa
August 30, 2015 8:26 pm
Found this sitting outside camper in Iowa and got a picture after the wife freaked out. Is this a horse fly?
Signature: Curious in Iowa

Female Black Horse Fly

Female Black Horse Fly

Dear Curious in Iowa,
Because of the spacing between the eyes, one can tell that this Black Horse Fly,
Tabanus atratus, is a female.  Only female Horse Flies bite and suck blood from mammals, and if they cannot find a four footed host, they will bite humans.  According to BugGuide:  “Although Tabanus atratus do not often bite humans, when it does happen it leaves painful memories. This fly can also transmit bacterial, viral, and other diseases such as surra and anthrax, to both humans and other animals through its bite.  The effect of T. atratus on livestock can be a serious problem. Blood loss and irritation from the flies can severely affect beef and milk production, as well as grazing. Livestock usually have no way of avoiding the painful bites, and millions of dollars have been spent trying to control these pests. (Long 2001)”

What's That Bug? does not endorse extermination

Subject: Black Moth?
Location: Bay Area, California
August 20, 2015 10:57 am
Just found this moth like creature in my garden this morning (8/19/15) in Fremont, California, zip code 94536. What is it?
Signature: Elizabeth Cerutti

Female Western Horse Fly

Female Western Horse Fly

Wow Elizabeth,
This is one gorgeous image of a female Western Horse Fly,
Tabanus punctifer, who can be easily distinguished from her sexually dimorphic mate by the spacing between her eyes and the color and pattern of the white hair on her thorax.  According to BugGuide:
“From Middlekauff & Lane:
Female: A large, dark-colored horse fly. Easily recognized by the following characteristics: mesonotum covered with creamy hair over a dark reddish background: remainder of thorax dark brown, with concolorous hair: wings brown, paler posteriorly, the cross-veins and furcation distinctly margined with brown; legs black, except basal third of fore tibiae, which are creamy white with long white hair; abdomen black.
Male: Color as in female except that the white of the mesothorax is confined to a lateral band and the outer margin of the scutellum.”
The pastel colors of the succulent plant act as a perfect background for this striking fly.  Female Horse Flies are blood suckers that feed on warm blooded animals, and many species are not at all opposed to sucking human blood.

Wow, thanks for such a quick, complete and descriptive answer!  I had no idea it was in the fly family, and a dreaded horse fly at that. When I was growing up on Long Island, NY, we used to try and dodge horse flies in the swimming pool in the summer.  They were so smart, they used to hover right above and wait for us to surface for air.  Hell of a welt.  This one today in the garden was easily an inch long.
Thank you, again.
Best regards,
Elizabeth

When we were putting together our response for you, we searched our archives for an image of a male Western Horse Fly to no avail.  Should you happen to see one, please take an image and send it to us.  Here is a BugGuide image of a male Western Horse Fly.

What's That Bug? does not endorse extermination