Antennae

 
What is unusual about this fly macro, is the brush antennae, that you might expect from a mosquito or a night moth. I do not recall ever seeing it on this type of bottle fly.
 
I have been very busy today, so no time to research, but I will be looking into this in the near future, as I take more of an interest in flies.

Update 1 - I went through my entire collection of flies and only found one other with a brush antennae, other than mosquitoes of course. It was obviously not closely related. A lot of research to follow.

Update 2 - I did some reading in the early hours; for this kind of fly, I only found a couple of mentions of feathery antennae. However, the correct scientific name for this antenna is plumose antennae. Once you know this and do a new search, a lot more information comes to light.

It seems all male bottle flies (Calliphora) have plumose antennae to a certain extent, but usually not as pronounced as this image. Very little is written on its function, but it is obviously for finding a mate. One article mentioned that  it is used for picking up the sound of the females wing beat, written in reference to a mosquito. Well, that could lead to some unfortunate mistakes.

Another article about moths states that the antennae are used to smell the pheromones emitted by the female and are extremely sensitive. This sounds like a much more accurate application.
 
Dave