Garlic mustard is in bloom right now both in its native Europe and in North America, where it is typically considered an invasive plant. Here is a shot of it in its native range (The Netherlands):
Bibio lanigerus ( or marci?)/Alliaria petiolata - Kleine rouwvlieg/look-zonder-look
Originally uploaded by AnneTanne.
And here it is again in the USA:
Both are being visited by insects that are likely pollinating the flowers.