It was Biblical.
No one had seen it before or since.
Sometimes nature 'burps'.
Here in Michigan, the Lake St. Clair shore line is fish fly heaven when they hatch in early summer....The city of Algonac, which is on the lake, hosts an annual Fish Fly Festival........
Back in the late 70’s in Austin, TX the entire Lower Level of IH-35 was covered with so many Crickets that it was Black concrete side walls. We even found them inside the 10 MB Dinner Platter sized HDD in the Computer and crashed it because crickets got stuck in the Read/Write Heads and the Disk.