Feathery is maybe misleading. You have to get very close to see the arista on Mycophaga clearly. I attach one of my own photos where you can see how difficult it can be.
This one was taken with a Raynox converter on the front of my Canon macro lens - and on a tripod. If you go looking for the flies in the early morning - before they have warmed up properly - you can sometimes get surprisingly close to take photos such as this one.