black horse fly

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Black horse fly occurs in the United States mostly east of the Great Plains and in adjacent Canadian provinces. At ¾″ to 1″ (20 to 25 mm) in length, it is one of the largest horse flies in North America. Some sources, including National Audobon Society Field Guide to Insects & Spiders (1980) and some Websites, suggest that it can get up to 1⅛″ (28 mm) long, but this is not widely accepted.

There are two large compound eyes and three simple eyes (ocelli). On the male the compound eyes meet at the top of the head. On the female they do not. The third segment of each antenna has a prominent tooth-like process at the base.

The body is stout. The body and wings are black, purplish-black, or dark brown. The thorax is covered with short, fine, black, yellowish, or whitish hairs. The wings are entirely dark, not patterned. There is no spur at the tip of the fourth segment (tibia) of the hind leg.

Total length: ¾″ to 1″ (20 to 25 mm)

Agricultural and suburban areas; any moist habitat with livestock or other large mammals

Spring to late fall

Black horse fly females prefer to bite cattle and other livestock. It is unusual for them to bite humans, but when they do the bite is memorable. Males do not bite.

Females feed on mammalian blood. Males feed on nectar and plant juices.

Sources

24, 27, 29, 30, 82, 83.

Infraorder
Orthorrhapha was historically one of two infraorders of Brachycera, a suborder of Diptera. However, Brachycera did not contain all of the descendants of the last common ancestor (paraphyletic). It was split into five extant (still existing) and one extinct infraorder. Orthorrhapha is now considered obsolete and has not been used in decades, but it persists in printed literature and on some online sources. A recent revision of the order Diptera (Pope, et al., 2011) revived the name Orthorrhapha, but this has not been widely accepted.

Why did this come to my house?? I’m hoping you can talk to their leader and ask them to stay on the farms.

(It was found already deceased.)

Why did God make these??

Black Horse Fly

I wanted to submit the black horse fly we discovered in Eden Prairie, MN! Never seen such a thing but compared it to the pics on this site! Truly fascinating and a tiny bit scary if you’ve never seen one before!

Was bringing groceries in the front and this guy was sitting on our siding. Never seen them around here in Onalaska WI.

I saw it fly into my shed pretty hard and fall onto the ground near my bird bath. I thought it was a cicada so I went to investigate. Took awhile to spot it on the ground, but when I did i knew it was not a cicada. We gained each other's trust to where I used a stick to let it crawl on and set it up on the bird bath where it seem to drink and clean its beak. It eventually flew towards my face so I scrammed!

I looked at the pictures of the Black Horse Fly, Tabanus atratus, at Minnesota Seasons and noticed that there isn’t a good closeup of one. I took the pictures in my backyard in La Crescent.

Huge Fly

I am in Itasca County and saw this huge guy on the sidewalk at 7 am and have never seen anything like this. I found your website and realized they are not normally in our area so I thought I would report my sighting.

Has anyone seen this before? It’s the size of a quarter for sure and reminds me of a horsefly with a huge “beak” to bite you with.

I decided to measure it since it was still there.

I did a little research and it looks like it is a black horse fly and not normally in this area. It is a biggun'!

So dark and large, she seemed velvety!

this site used to be location of dairy Cows and Horses

Location: Mendota Heights, MN

Why did this come to my house?? I’m hoping you can talk to their leader and ask them to stay on the farms.

(It was found already deceased.)

Location: Two Harbors, MN

Why did God make these??

Location: Eden Prairie, MN

I wanted to submit the black horse fly we discovered in Eden Prairie, MN! Never seen such a thing but compared it to the pics on this site! Truly fascinating and a tiny bit scary if you’ve never seen one before!

Location: Onalaska, WI

Was bringing groceries in the front and this guy was sitting on our siding. Never seen them around here in Onalaska WI.

Location: South Saint Paul, MN

I saw it fly into my shed pretty hard and fall onto the ground near my bird bath. I thought it was a cicada so I went to investigate. Took awhile to spot it on the ground, but when I did i knew it was not a cicada. We gained each other's trust to where I used a stick to let it crawl on and set it up on the bird bath where it seem to drink and clean its beak. It eventually flew towards my face so I scrammed!

Location: La Crescent, MN

I looked at the pictures of the Black Horse Fly, Tabanus atratus, at Minnesota Seasons and noticed that there isn’t a good closeup of one. I took the pictures in my backyard in La Crescent.

Location: Cohasset Elementary School in Cohasset

I am in Itasca County and saw this huge guy on the sidewalk at 7 am and have never seen anything like this. I found your website and realized they are not normally in our area so I thought I would report my sighting.

Has anyone seen this before? It’s the size of a quarter for sure and reminds me of a horsefly with a huge “beak” to bite you with.

Location: Otsego, MN

I’ve never seen a fly that big before!

Location: Aiken, South Carolina

Very large for a fly. So black it seemed velvety. Resting on my porch.

Location: Maplewood History Barn Maplewood, MN

this site used to be location of dairy Cows and Horses

Location: Maple Grove, MN

Not sure what kind of fly this was (maybe you do), but Norm didn’t want to get too close! Darth Vader? It was on our patio umbrella post. Yikes