Nice series! I'm curious about the thing near the attachment of the left wing. It looks almost like a calypter. I guess it could be fungus, maybe. I am about to post a photo of a drosophila with something a bit like it. Maybe some sort of parasite. But it sure looks like part of the fly. I will link to it when I post it, if the answer does not become obvious.

I suspect you are referring to a haltere.

I was thinking that acalyptrates did not have halteres. I must have just forgotten because they are small enough that I don't guess I've actually seen them lately. I actually sort of like this group of flies, but my photos on this scale aren't always detail rich.

This is off topic but I love your macro set up! It is well in advance of mine, but a lot of the tips I will want to try. The Yongnuo is a nice ring flash, except you need to be very careful with the battery compartment door. The tab that keeps it closed broke on mine! I love your softbox!

I did notice a haltere, one a fly I shot the other day. I normally (always?) shoot hand held but I can see the benefits you have reaped with your techiques.

Cheers!
-Arthur
Thanks for sharing your knowledge!