#1
These pictures were taken (with a strong risk of tumbling down into the water - luckily enough I put my gum-boots on) near the railroad's embankment at the edge of a small pond where blocks of a cut down aspen tree were lying.
I think the first species was scared away from vegetation by my noisy approach to sit either on these tree blocks or small branches that remained on them. Rather big, 4-5mm, moving slow, and very dark in appearance (I just had to ajust levels in order to reveal more details). Maybe a
Notiphila?
#3
The second species was smaller, around 3mm. I saw mating flies, too, but unlike Nikita
wasn't able to capture the process
, it was so quick. Maybe a
Hydrellia sp.?
#5
I agree with Nikita - the first one is Notiphila (s.g. Dichaeta) caudata female - the males have very long strong bristles on the end of the abdomen.
The other is a Notiphila, but I wouldn't like to say which species without examining the genitalia.