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Your analysis is nearly perfect, however, you forgot about females.
Bothria and Panzeria puparum are totally not related but look very similar in the field and they both fly in april.
In Bothria, the third antennal segment is very long, in Panzeria short. Moreover, the short broad tarsal segments well shown in your pics are a clue.

So, female Panzeria puparum it is.

Theo