How exciting, a pyrgotid fly! They are attracted to lights, perhaps, because they are parasitic on adult May beetles (Scarabaeidae: Phyllophaga spp.). From what I understand, they molest the beetles in mid-air, and the female forces an egg between the victim's abdominal segments. The larva that hatches then feeds internally. I did not know this family occured in your area, but here is proof positive! Very nice image.