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

Subject:  horsefly?
Geographic location of the bug:  Florida
Date: 07/05/2018
Time: 09:13 PM EDT
Your letter to the bugman:  Is this a horsefly?
How you want your letter signed:  uh

Deer Fly

Dear uh,
This is a Deer Fly, not a Horse Fly, but they are in the same family Tabanidae, so they share many similarities.  We believe your individual is in the genus
Chrysops, and according to BugGuide:  “100 spp. in 2 subgenera in our area.” Alas, we haven’t the necessary skills to provide a conclusive species identification.

What's That Bug? does not endorse extermination

Subject:  What the hell is it??
Geographic location of the bug:  Bassenthwaite Cumbria England
Date: 07/01/2018
Time: 12:20 PM EDT
Your letter to the bugman:  Please help me with what the hell this is!!
How you want your letter signed:  Gail.

Giant Horse Fly

Dear Gail,
Congratulations on being chosen Bug of the Month for July 2018 with your query of this Giant Horse Fly, in the genus
Tabanus.    You are the third identification request we have received this week, and we quickly linked to a Huffington Post posting.  We cannot tell due to the camera angle if this is a male or female Giant Horse Fly.  Males in the genus have compound eyes that nearly touch one another while the eyes of the female have a space between them.  Only the female Giant Horse Fly will bite as the male does not feed on blood which is necessary for the female to lay viable eggs.  That blood generally comes from livestock including horses and cattle, but when livestock or other large mammals are not available, the opportunistic Horse Flies might bite humans, but try to remember after viewing the images on that Huffington Post article that most encounters between humans and Horse Flies do not end with bites.  The Gadfly that tormented Io in Greek mythology was most likely a Giant Horse Fly as Wikipedia confirms.  Long ago, the mythological Io was also the inspiration for the name of the lovely North American Io Moth as was consistent with the pattern set with 18th Century taxonomists like Linnaeus and Fabricius.

What's That Bug? does not endorse extermination

Subject:  Can you confirm my suspicion that this is a horsefly?
Geographic location of the bug:  Scotland
Date: 06/29/2018
Time: 02:17 PM EDT
Your letter to the bugman:  Hi, I have been finding these guys lying on their back in my back garden regularly (4 in the last 2 days). I thought they may have been honey bees.
I flipped them all back onto their feet only for them to roll back over.  It has been unusually warm here.
They are around 20mm in length.
I am a little concerned by the number of them appearing in my back garden because my 2 young children play there regularly.
Thanks in advance.
How you want your letter signed:  Kev

Horse Fly

Dear Kev,
This sure looks like a Horse Fly to us.  The wing venation pattern matches the diagram posted to BugGuide.

What's That Bug? does not endorse extermination

Subject:  Unidentifed Fly
Geographic location of the bug:  Somerset, UK
Date: 06/25/2018
Time: 06:45 AM EDT
Your letter to the bugman:  This fly was in my house in Somerset, UK this morning. I am unable to identify it because it was so large. The body was 35mm long. The eyes were green matt (olive/emerald). It buzzed loudly. This is much larger than the Giant Horse Fly known in the UK. Please can you help?
How you want your letter signed:  Liz

Horse Fly

Dear Liz,
This is a female Horse Fly in the genus Tabanus.  Horse Flies often plague livestock by biting to feed on blood, but only the females bite.  We located an article on Huffington Post that states:  “
Forget giant hogweed, horseflies are the newest atrocity plaguing the nation.  People across the UK have been sharing photos of their horrendous horsefly bites – and it’s enough to put you off your dinner.  The flies, which are large, dark-coloured and 1-1.2cm in size, are often found loitering around farm animals (such as horses and cattle), ponds and other grassy areas.  Their bites cut the skin, rather than piercing it, which can be very painful.”  Your fly might be the Dark Giant Horse Fly, Tabanus sudeticus.

Thank you for your quick reply. I am very familiar with our common horse flies but this one was nothing like them in size. This one was 3.5cm (35mm) long with a much wider body and not the normal 1-1.2 cm. I have also looked up the Dark Giant Horse Fly but the recorded maximum size for that type seems to be 2.5 cm. This was definitely something you would not like to bite you. I am now wishing I had trapped it rather than letting it go!
Many thanks for getting back to me.
Liz

What's That Bug? does not endorse extermination

Subject:  What’s this clutch?
Geographic location of the bug:  Southern Ontario
Date: 06/21/2018
Time: 08:19 PM EDT
Your letter to the bugman:  Looked up and saw this on a Norway Maple leaf.  Moist to the touch.   Looked like a fat little moth.  Actually made of overlaid cylindrical units.  Egg clutch?
How you want your letter signed:  Mike

Horse Fly Eggs

Dear Mike,
These sure look like Horse Fly eggs to us.  Here is a BugGuide image for comparison.  According to Purdue University:  “Females search for a place to lay a single mass of eggs consisting of 100-800 eggs, depending on the species. Egg masses of most species that have been studied are laid on the underside of leaves or along the stems of emergent vegetation growing in wetlands. Hatching occurs in approximately 2-3 days, and newly emerged larvae drop down into water or saturated soil in which they feed and develop.” 

Horse Fly Eggs

Thanks! No water near there for the larvae to drop into and mine were a silvery-blue colour (vs the pic; likely varies anyway, right?) but if it’s any of those bitey buggers (Tabanidae), then I don’t feel bad for disturbing it.  Now I know.  Tough to pick the keywords to search these things.  You all do a very cool service.  Great site too. Thanks again.
Mike
Hi again Mike,
Online images of Horse Fly eggs do vary in color.  Larvae of some species will develop in damp soil.
On subsequent inspection, it seems that egg mass must have just been fresh; thus the bright colour.  They dried to a dark brown/black.
Thanks for providing that additional information.
What's That Bug? does not endorse extermination

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

What's That Bug? does not endorse extermination