Mayfly

6401  Small and long flying bug with three tails. They have resided on our balcony. There’s at least 50 of them. I had swatted them all away (some dead) and they came back in greater numbers a few days later. We live close to a river and do not have any lights on our balcony. CALGARY, Alberta. Canada

Number 6401. This is a mayfly (order Ephemeroptera). These spend most of their lives as nymphs/naiads at the bottoms of streams and lakes where they constitute an important part of the feed web there. The adults you see seldom live more than a day; just long enough to mate and lay eggs. They do not feed and are completely harmless.