Mydas Fly

peach borer or mimic?
Location: powhatan county, virginia
June 17, 2011 10:22 am
there is a low-cut, decomposing stump in my flower bed, from a tree felled many years ago (hardwood, not fruit). when tending the flowers, i noticed and collected this insect, as well as several pupae cases (from which another like insect was emerging), from around the base of the stump on june 16, 2011.
i am not convinced it is a peach borer, because the antennae are very different, as are the eyes/head – more fly-like. the orange band is higher up on the abdomen, and the wings at rest fold over one another. i’m fairly certain it has only one set of wings. any info would be appreciated!
Signature: bugwatcher

Mydas Fly

Hi bugwatcher,
This incredible creature is a Mydas Fly,
Mydas clavatus, and according to BugGuide, it is a:  “Large black fly with red/orange mark on top (dorsum) of 2nd abdominal segment. Body hairless, cylindrical. Eyes large. Antennae are distinctively clubbed in the Mydidae. This species flies rather boldly in the open. With the black-and-orange pattern, it resembles a wasp and fools the casual observer.”  The larvae live in compost piles, soil and rotting wood where they feed on June Beetle Larvae.  According to BugGuide:  “Eggs are laid singly in soil or rotting wood. (See video of oviposition–Flickr). Mydas larvae prey on beetle larvae, esp. those of June beetles. Larvae pupate close to soil (or wood?) surface. Adults are active only in mid-summer. Mating system in this species unknown.”  You are observant in noticing that the Mydas Fly, in addition to mimicking Spider Wasps, looks very similar to a female Peach Tree Borer.  The Peach Tree Borers are also wasp mimics, as you can see in this photo from our archives.

Mydas Fly Pupa

thank you so much. the more i talked about fly characteristics, i looked up all the flies on your site, and found Mydas after i had sent my email. i was thrilled to discover what it was, and promptly let it go. a beautiful fly, and a garden helper at that. when it flies, it has a very nice low buzz, also wasp-like and intimidating. i feel fortunate to have been able to examine it so closely during it’s brief adult stage. thank you again for your prompt response and devotion to the site.

8 thoughts on “Mydas Fly”

  1. Is it common for this bug to be in south eastern Massachusetts? If not would it be considered to be an evasive species?

  2. I just saw a mating pair connected flew by me and landed on a tree I live in Putnam county,NY amazing looking fly!

  3. I just happened on this site while searching for ID on an unfamiliar insect seen in my garden area today. It was on an old wood pile and flew away quickly into nearby Green Giant Thuja trees. There appeared to be two of them. I am glad to know it is not an invasive or destructive pest.

  4. I live in Christiansburg VA.
    While flipping my compost pile a jet black wasp with an orange band landed.I never seen one until yesterday.after a Google I came across this site.It is a mydas fly so glad it’s not a wasp that stings.


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