Giant Horsefly

2011 November 5

On July 26, I was walking between buildings on the Michigan Tech campus when I saw this very large (and fortunately very dead) horsefly lying on the ground:

How large was it? Well, its body was a full inch long, which for a fly is positively monstrous.

This looks like one of the horseflies in the genus Tabanus, a diverse genus that includes some of the largest horseflies.

There are several large Tabanus species that look kind of similar to this one, but I think it is most likely Tabanus catenatus based on the uniformly gray, unstriped eyes, the dark brown legs, the row of small white triangles running down the back of the abdomen, and the slightly smoky, unspotted wings.

I think that it’s a female, because the eyes don’t grow together in the middle to cover the whole head like the eyes of a male fly would do. Which means that she’s one of the ones that would bite. And given her size, a bite would have been pretty darned painful. I’m glad she was dead.

The larvae are aquatic and carnivorous, eating other insects that they find. Some species of horsefly spend a couple of years as larvae before they mature, and given the size of this one, she’s probably one of them.

A note: this is posting number 250. And so we forge onward!

5 Responses
  1. November 5, 2011

    Good photos, but…Yuck! I’m only too familiar with horse flies and the damage they can inflict.
    Check out this picture of my horse:

  2. November 6, 2011

    Yikes! That poor horse! I guess the base of a horse’s neck is kind of a vulnerable spot where horseflies can attack easily.

  3. Della3 permalink
    November 7, 2011

    I had a bad experience with horse flies after a sunset swim on a beach many years ago. Ouch! Now I understand why the bites were so very painful.

    Sheri, I love your blog! Thanks for stopping by! I knew horses could pitch a rider off from a rattlesnake siting or an unexpected pothole. It never occurred to me that the same could happen from a nasty bug bite. How precarious for the riders! It’s amazing that horses have been used as a reliable transportation source at all.

  4. November 8, 2011

    Congrats on post #250! That’s quite an achievement given the work behind each one.

  5. Raymond permalink
    July 19, 2017

    The fly I killed yesterday is a inch and a half long !!! In white lake Michigan

Comments are closed.