WATCH: Rhode Island beachgoers stunned by 'dragonfly apocalypse'

A swarm of dragonflies startled beachgoers over the weekend at Misquamicut State Beach in Westerly, Rhode Island, in what one witness described as a “dragonfly apocalypse.”

The swarm flew in as people were enjoying the beach on Saturday, creating a noise that was said to be as loud as an airport.

“We kind of looked to the left and there’s this black cloud and they were swarming from over the ocean and then right before you know it they were in front of you, beside you, they were just everywhere … It kind of felt like an eternity, but I would say it probably lasted between 2 and 4 minutes,” beachgoer Nicole Martin told Boston ABC affiliate WCVB-TV.

While the swarm did not linger on the beach, the flying insects remained in town.

“As the day went on there were tons of them everywhere. We had to close the doors,” Christina Vangel, a worker at Alfie’s Surf Shop in Westerly, told the Associated Press.

One expert says the swarm was migratory in nature. Connecticut Agricultural Experiment Station Associate Scientist Gale Ridge said the bugs were green darner dragonflies, according to Hartford, Connecticut, CBS affiliate WFSB-TV.

The dragonflies “may have been pushed on shore by the wind” and she likened their visit to a family stopping for food on a road trip. Dragonflies eat midges and mosquitoes, and the swarm was “the arrival of the cavalry as far as mosquito management is concerned,” Ms. Ridge said.

Green darners are common in the area and breed in July and August, according to the AP.

Another expert thinks that, instead of the migratory green darners, the swarm was made up of another local species, blue dasher dragonflies.

North Carolina Museum of Natural Science Head of Citizen Science Chris Goforth told the Boston Globe that Saturday’s horde of dragonflies could have been a “feeding swarm” arising from a sudden increase in standing water that in turn gave mosquitoes more places to breed.

If the swarm was made up of blue dashers, habitat issues could also have been at play.

“There being so many in one place like that is unusual,” Ms. Goforth told the Globe. She thinks that the swarm suggests that the dragonflies were either searching for food or that there is “something wrong with their habitat so they’re moving to a better place en masse."