Living in Dubuque during high school. I witnessed the mayfly phenomena. Remember bridge over Mississippi being closed because they made it slick as ice. They only live a short time and the millions of stacked up rotting corpses put up a beyond wretched stench.
The funniest thing was seeing two guys pulling their boat into the marina while yelling they were going to get stung to death by them. Their boat had 3 or 4 inches of dead Mayflies in it.
Funny and nasty all at the same time.
L