#2
Astonishing.

The fly with the prey is an asilid but is the newcomer? Looks like it. I associate this behaviour with Empididae -males offering seductive gifts to females

. I'll see what I can find on this when time allows. Perhaps Geller-Grimm could help.
#3
I think both flies are robber flies but they do not look like the same species. I have not heard of kleptoparasitic behaviour in asilids yet, but I can have a quick check.
EDIT: Nothing in this one:
http://www.dipter...load_id=11.