Zeegers wrote:
This is either B. marci or B. hortulanus.
Hortulanus fits your description best.
Thanks! But the problem is: I have never seen an orange female here over the years. Yesterday afternoon not only the small B. johannis were flying, but now also many Bibio (cf.) marci males and some females. All completely black (and slightly bigger than the above one), except one female with reddish legs (B. lanigerus?).