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Flies in peony stems

Posted by phlowerpower 5 (My Page) on
Sun, Jun 29, 14 at 21:05

The cut tips of several peony stems had signs of borers--I could see the inside material of the stem powdered and on the lower leaves. I split a stem in half and found several small flies inside the stem. They showed no sign of life. I am pretty sure they are small flies--they have the typical fly shaped wings and large eyes. I am just so curious to learn more about the life cycle of these flies. I have about 6 more peony stems with the same signs of borers. Anyone know what they are?

Follow-Up Postings:

RE: Flies in peony stems

Oh, how interesting. You have a great example of biological control in action!

This is a relatively common phenomenon in which a predator insect hollows out the soft pithy center of a stem in order to lay its eggs.

Do you see the tan "plug" at the far left and another towards the right? That's evidence of a small predator wasp which is stocking each cell (the space between 2 plugs/partitions) for its youngsters. The prey are alive, but stunned, and will provide fresh "food" for the predator's young.

One cell per youngster. Many prey per youngster; with more prey for females than for males.

I'm curious where you live. Please tell us city & state.

RE: Flies in peony stems

I was thinking it looked as though these flies were being stocked up by some other creature. Ok I am off to look up more info about wasps doing this. I live in Iowa. Thanks for the reply!

RE: Flies in peony stems

Fascinating, jean! This one really had me scratching my head. The image was perplexing, to me. Any idea what genus of wasp this might be?

RE: Flies in peony stems

No I don't.
And I would like to know if the prey truly are flies. I can't see enough detail to be certain.

Okay, this is the back story. I have a friend who is a fanatic about monitoring & documenting mason bees in the local Master Gardener demo garden.

And since he started, he has seen several predatory wasps also using his bee nests.

If you're interested, reserch these:
- Isodontia elegans, common name the grass-carrying wasp -- a wasp about an inch long; prey are tree crickets
- Passaloecus species -- a very small predatory wasp; prey are aphids

This post was edited by jean001a on Tue, Jul 1, 14 at 17:25

RE: Flies in peony stems

Here is a photo of one of the insects in the stem. Has fly shaped wings and eyes as far as I can tell.

I am only seeing signs of activity in my cut peony stems. So fascinating! I haven't spotted the creatures doing this though.

RE: Flies in peony stems

I think you're correct. Can't see antennae but can discern the shape of the head.

RE: Flies in peony stems

Thanks to folks like Jean (and rhizo, for that matter), I never stop learning. That's a new one for me.


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