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I photographed this fly in August, near Chicago IL USA. I'm wondering, is this Ptilodexia sp.? And, what's going on at the rear end, there? Thanks for any help.

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Not sure why all images did not u/l oh well here are the others.

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lastly:

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Hello Bruce,
I don't know American insects very well, but this one seems more like a member of the family Sarcophagidae to me!
Like I said, I could be wrong, and there are maybe Tachinids there that resemble Sarcophagids a lot.

And what is going on at the rear end: this is a male, and what you see is the genital apparatus, one of the tergites/ sternites bends down and back underneath the fly's belly.
And because it's red, it's clearly visible as a red knob at the rear end!
Greetings

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Hi Gerard,
Wow, thanks for that redirect. I believe you are correct on the family, and I think I found the genus, Sarcophaga. Check the pictures here and see if you agree?
http://elib.cs.be...ophaga+sp.

Thanks again,
Bruce

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Hai Bruce,
Yes, I think so!
However, the best way to confirm the identity is by using a family key.
Tachinidae have a very well developed post-scutellum (the region directly underneath the scutellum) whereas in Sarcophagidae that shouldn't be like that. This criteria is used to split the Tachinidae from the rest of the Calyptrata. Although I must admit it is sometimes not easy! But than you should have collected the fly.....

Have some nice Christmas days and a happy, fly-rich new year!

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So, Gerard solved the mystery already.
It is indeed a male of the family Sarcophagidae, subfamily Sarcophaginae. If it is from USA, then it is unlikely to be Sarcophaga ss., because this genus is predominantly Palaeartic.
So one can use the key to genera in Manual of Nearctic Diptera.
However, in many cases the male genitalia are of importance, so identification may prove troublesome.


Theo Zeegers

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Hello Theo,
Thank you for that input. Once Gerard gave me the family, I started finding pictures all over the www. I emailed my pictures to Thomas Pape at the Zoological Museum, University of Copenhagen. He confirmed the genus as Sarcophaga - but, like you, he stated the genitalia as critical to species identification.

Hell, I'm happy to have a genus!!
http://cirrusimag...ophaga.htm
Thank you all for your help. It's very frustrating for a rank amateur such as myself to "pin these guys down", as I don't collect them, I just take pictures.

Regards,
Bruce Marlin