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Mud dauber parasites?

Mud dauber parasites?
Oak Ridge, Anderson County, Tennessee, USA
July 17, 2008
Size: 3/4"
I found these dried larval "skins" left in the holes of a mud dauber wasp's nest. They appear to be from a wasp parasite. Some holes had 2 of these emerging from them. Could they be from a tachnid fly? Does anyone recognize these? Thanks!

Moved from Bee Flies.

Bee fly seems right
I just came across this paper on identifying bee fly pupae in the genus Anthrax, and these do look like them. There are some that are known parasitoids of mud daubers.

That looks like a good match!
Thanks Charlie! According to the Kaufman Field Guide it looks like a good match. Anthrax, what a strange genus name for a fly!

Mud dauber "parasites"
Hi Eric,

Oh gosh, you've asked me a lot of questions that I can't answer! I was shown the nest at the University of Tennessee Arboretum in Oak Ridge. I never saw the adults at the nests, so I have no clue what they looked like. And I'm assuming the round holes were the exit holes, but I don't know if they were made by the wasps or these creatures. This may be a mystery that will have to go unanswered!

Hi Kris,

Well, I'm not sure what these are, but I can tell you they definitely aren't from tachinids. The nest looks like probably a pipe organ mud dauber (Trypoxylon politum, what Eric's calling Trypargilum), but I'd want to see a photo of the whole nest to be sure.

Any chance you could get a more detailed shot of the exuviae? I'm curious to find out what they are too! They remind me a bit of carpenter bee pupae...

These could belong to a parasitic species of Bombyliid. I took apart a Trypoxylon politum nest last December to see what parasitoids would emerge, and a fairly large black Bombyliid was one of the emergents. The exuvia looks very similar to the ones in the picture (it's at home, so I'm going by memory).

Here is the only image I could find of a bombyliid pupal skin, for comparison.

I should modify my previous comment to say, they remind me of pupal skins that I found below carpenter bee holes when they were doing "spring cleaning." What I found looked more like Kris' photo than like the one in the attached link, but I may well be wrong about what they were.

Parasite or scavenger....
Was there an exit hole from the wasp emerging, or was the nest still sealed aside from these things poking out? If sealed, then, yes, some kind of parasite (probably a fly). If an exit hole from the emerging wasp, then probably some kind of scavenger eating the spider remains. Also, what kind of mud dauber (Sceliphron, Chalybion, or Trypargilum)?

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