LAKE WACCAMAW, N.C. (WNCN) – Residents at a North Carolina lake are still stunned by the size of a swarm of insects earlier this month.

Large groups of mayflies are known to gather around Lake Waccamaw every April, but residents said this year’s massive swarm of millions of aquatic insects was the worst in 30 years.

Lake Waccamaw has about 9,000 acres of surface area and about 14 miles of shoreline.

The yearly swarm of the mayflies is known by Lake Waccamaw fishermen to mark a point when the fish in the lake become more active. Mayflies have a short-lived adult phase, which usually lasts from two hours to three days, according to flyfishingnc.com.

On April 13 and 14, there was a large “invasion” according to one resident who took photos of the mayflies swarming her truck and her home, and gathering around lights.

The insects even covered a nearby road.

“The invasion of the mayflies!!!! Unreal!!” one woman wrote on Facebook.

The gathering earlier this month was largely seen on vertical surfaces, but also included large amounts on the ground — enough to sweep in some areas.