#1
First time meting Bibio I thought that it is Hymenoptera.
Now I know that it is Bibionidae male. Looks different from Bibio genus. On Solidago, 6vv, around Moscow, 09 sept. Dilophus?

#2
There is little to teach you, these day. Indeed it is a species of
Dilophus. Maybe
D. febrilis but I am too unfamiliar with your area to say that it must be that species.
#4
Thank you Paul and Theo.
Only now I begin to understand how much I have to teach.
Well, there is in few month some progress from wandering what order to thinking which genus. And if realy so, it is good illustration how usefull is the Idea of this site!
Nikita