Botfly: A Vampire Insect as Horrifying as any Fiction

There are about 150 species of hairy flies that are known to be parasitic to mammals. Notably there is the Dermatobia hominus, the human botfly. This is going to be nasty folks.

The female botfly deposits their eggs on a living host, a mammal or even another insect which acts as a vector (a method of transmission) to a warm-blooded mammal. Eggs that are laid on a mammal come into contact with the skin and hatch shortly thereafter, fueled by the warmth of the mammalian body. From this hatching they burrow down under the skin where they take residence and grow larger, feeding upon the blood and fluids of the host for months.

Intestinal Invader, Internal Vampire


(image source)

Some species of botfly reside in the digestive tract of mammals, introduced by the licking of the afflicted sites of botfly egg deposition such as legs or feet, where they act as an irritant. The type of botfly larva such as this is depicted above, resides in the intestines of large animal hosts such as horses and remain attached for nearly a year, feeding until they mature. They eventually release themselves and are passed via elimination to become adult botflies outside of the mammalian body, and the cycle of infestation continues. There are de-wormer medications that can be used to eradicate the botfly larvae in the host animal and hopefully break or interrupt the cycle of parasitism.

These insects in true parasitic form do not kill or actually unduly harm the host, but there are some species of botfly such as in the rodent-infesting variety that seek and consume the testes and ovaries of their host and thus rendering them incapable of reproduction. There is another type of botfly whose presence causes lesions under the skin that become infected by a bacterium they carry. This causes large bumps to form under the skin. Without antibiotic intervention, the host animal usually dies.

American Warble Fly

Growing up in western New York State I have seen what the American Warble Fly (a botfly species member) can do to both livestock and feral game animals. These botflies do not seek out humans as host but do attack larger mammals such as deer and cows. We had a milk cow that had about two dozen large bumps on its back, front shoulders and haunches that we were taught how to remove. Manual palpation via precise squeezing would cause the larval slug to erupt out of the animal’s back in a most disgusting manner! Think big, fat pimple that explodes when squeezed firmly and in the right way. These would come out like explosive child-birth, expelling the still-live white grub. I can still hear those damn things squirt up and hit the low ceiling of the milking parlor with a smack! Yuck!

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14 Responses to “Botfly: A Vampire Insect as Horrifying as any Fiction”
  1. I Have Had Enough Says...

    On January 11, 2010 at 6:41 am

    Stick, you have a way of adding the real graphic details, that you just don’t get on animal planet.

  2. drelayaraja Says...

    On January 11, 2010 at 7:15 am

    nice article : ) very informative

  3. Brenda Nelson Says...

    On January 11, 2010 at 11:04 am

    Every horse owner knows the botfly. They lay eggs on horses legs, tiny dots. When the horses itch their legs (with their mouths) they ingest the eggs who grow and develop into larva in the horses stomach where they attach themselves to the stomach lining. A severely infected horse cannot digest its food properly. Deworming is important.

  4. FlexionCalc Says...

    On January 11, 2010 at 12:54 pm


    Nice article though :-)

  5. clay hurtubise Says...

    On January 11, 2010 at 10:21 pm

    I’ve heard they taste like chicken!
    Good (gross) piece.

  6. R J Evans Says...

    On January 12, 2010 at 4:51 pm

    Ew. Nasty. Bleur, blarg, blogged at


  7. zoeyclark Says...

    On January 16, 2010 at 9:12 am

    I’m with Clay here- grossly good piece : D I am such a girl when it comes to insects. I am horrified by most and despise almost all : D

  8. JMPK89 Says...

    On January 21, 2010 at 4:29 am

    Oh god! My insect phobia just got even worse. Great article though! Probably why my insect phobia worsened :P

    – JM

  9. Abi Says...

    On March 18, 2010 at 5:01 pm

    why do people get them, where do they go??

  10. Ludanto Says...

    On April 13, 2010 at 5:45 pm

    For some reason it always seems like people get them in Belize. :)

  11. XXElleXX Says...

    On May 1, 2010 at 9:28 am

    Holy hell! I’ve heard of them but I didn’t know much about ‘em .. ewww they’re like a tick but different again .. grossed me right out Stick hehe thanks! ~ stumbled :-)

  12. 2Fluent Says...

    On September 6, 2010 at 11:32 am

    I want a white grub as a pet…

  13. Colin Says...

    On March 22, 2011 at 8:19 pm

    I removed the one from my arm fairly easily once I realised what it was.
    A black spot kept bleeding so I kept an eye on it. I then realised that it had healed with a vary large pore to the centre.
    Put a bubble of vasilne on it and the breathing tube rose above it.
    A pair of good tweezers and grabbed the tube. Pulled very gently and after a while I had a white pea with a tail!

  14. Botfly meat | Austinbeachvol Says...

    On September 12, 2012 at 7:46 pm

    [...] Botfly: A Vampire Insect as Horrifying as any Fiction | SciencerayQuick overviews and basic info on Botfly. A botfly, also written bot fly, bott fly or bot-fly in various combinations, is any fly in … Removal processes include pl… Latest news and videos on Bot… [...]

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