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I think that your identification is correct, T. aemula.
In T. aemula the occiput is not completely shiny, it is with smaller area of pruinosity than in T. arrogans (just a spot on middle portion). T. aemula is somewhat variable in wing length.
The best comparison of these species can be found in Collin's British Empididae (p. 85).

Best wishes,
Igor Shamshev