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Botfly Puparium

Congratulations on some very creative guesses!  Yesterday’s post  was a botfly puparium – a hard case made from an insect’s larval exoskeleton (skin) that covers and protects the pupa.  Most insects that go through complete metamorphosis (egg, larva, pupa, adult) don’t have this added protection for their pupal stage, but certain flies, including botflies, do.  Botflies are fairly large, hairy flies that resemble bumblebees and are internal parasites of many species of mammals, including humans. Depending on the species, the botfly deposits its eggs on or near the host animal, or on another insect, such as a mosquitoe or housefly, which carries them to their host. The eggs of some species of botflies are ingested or inhaled; those of other species hatch and the larvae bore into their host. After entering and crawling around inside of the host animal for a week or so, most species of botfly larvae settle in a spot just under the host’s skin and remain there for three to ten weeks, consuming the flesh of its host.  The lump, or “warble,” that forms just under the host’s skin where the botfly resides increases in size as the larva grows. A tiny hole chewed in the skin allows the larva to breathe, and eventually it exits through this hole.  The larva falls to the ground, where it pupates in the soil and later emerges as an adult botfly. (The two yellow bumps at one end of the puparium are spiracles, through which the pupa breathes.) The whole story of this particular puparium is that Jeannie Killam  found it in her old farmhouse’s kitchen cupboard, where it probably popped out of a visiting mouse.  (Illustration is of a human botfly.)

7 responses

  1. Luane Clark

    Thirty or so years ago one of our cats developed an unusual, marble-like lump on its back just behind his shoulders. The lump had a tiny hole in it. We could see something was moving behind that little hole. Our vet at the time recognized it right away, although it was a fairly rare phenomenon in cats; he had observed it more often in pigs and cattle. So he took care of it, but because it was unusual in cats we were very surprised to discover another one on this same cat some time later… And now thanks to your post I am reminded of this incident with one of my favorite cats and know a lot more about just what that was!

    July 28, 2012 at 12:16 pm

  2. John DeWitt

    I have seen one exit from under a mouse’s skin, right after the mouse died-very interesting, but also a little unsettling.

    July 28, 2012 at 1:08 pm

  3. Susan Holland


    July 28, 2012 at 3:56 pm

    • John DeWitt

      That’s what I said!

      July 28, 2012 at 4:48 pm

  4. Ned Jacoby

    “Nature in the raw is seldom mild”

    July 28, 2012 at 6:36 pm

  5. Phyllis

    I had a huge thing like the Bot-fly look me in the eye. I wasn’t sure if it wasn’t a bumblebee hummingbird. I have never seen anything like it. I thank you every day.

    July 29, 2012 at 8:46 pm

  6. Schuyler Gould

    Pretty creepy. I’ve got an itch.

    July 29, 2012 at 10:32 pm

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