This picture is of Lucilia_caesar captured in the Sheffield area of South Yorkshire UK
The arista of the upper antenna above
The male genetalia from the side
I have taken 4 pictures starting from the apex of the hypopygium.
2. After quite a wide gap comes this pair of pale processes with a short
darker one inbitween.
3. Followed by a pair of processes with spines on the end, with the base of
an unpaired object.
4. Finally the large unpaired process which I take to be the penis, phalus or
aedagius, I'm not sure of the spelling.