LINCOLN SQUARE — A swarm of beetles have invaded Welles Park where a previous grub infestation had made the grounds unusable.

Since at least July 6 thousands of beetles have been swarming the baseball fields on the eastern side of Welles Park, 2333 W. Sunnyside Ave.

A Block Club reporter observed the July 6 swarm of beetles haphazardly circling each other as they flew in the air a few feet off the ground also as they crawled around the grassy field, climbing over each other.

It appeared they were also burrowing under the green landscape of the field that day.

A swarm of beetles at the eastern side of Welles Park the afternoon of July 6, 2026.

After reviewing the July 6 footage from Block Club, state entomologist Christopher Dietrich confirmed what he saw is the same species of June beetle that has plagued Welles Park in the past.

“These are definitely green June beetles,” Dietrich said. “Probably some combination of males flying around seeking females and females flying around looking for places to lay their eggs.”

At this point in their lifecycle the adult female beetles secrete a pheromone to attract males for courtship and mating before laying their egg clusters in the soil, he said. The grubs will hatch “a couple weeks later,” he said, and will feed on organic debris and decaying plant roots. They spend the winter deeper in the soil.

Many residents have started to take notice.

North Center neighbor Zach Koutsky estimated that a video he posted to X (formerly Twitter) Saturday showed “thousands” were in the park over the weekend while his kid was playing baseball.

“It was amazing,” Koutsky said.

Around 7:45 a.m. Saturday his 10-year-old son was at the park playing baseball as part of the Welles Park Parents Association’s year-end celebration which included all-star games and home run derbies, he said. That’s when they noticed the beetles.

“We’re sitting in the stands and see all the kids in the outfield like swatting at stuff,” Koutsky said.

Uhh, the Wells Park grubs have all grown up by the thousands. @BlockClubCHI pic.twitter.com/JzaQA0IoWc

- Zach Koutsky (@zakouts84) July 11, 2026

Kids in the dugout were also swatting away the beetles, which were flying around in a “very dopey” manner, he said. They weren’t biting but they fly into many people while they were out on the fields and created an eerie buzzing sound the entire time, Koutsky said.

“As it got warmer, or maybe because the field got more disturbed because there were more kids out there, you really saw them swarm. They were just everywhere.”

Coaches were yelling at kids to stay in their positions in the outfield and the players were yelling back, “You get in the outfield!” Koutsky said.

“It looked otherworldly,” Koutsky said.

One beetle, about the size of quarter, flew behind Koutsky’s sunglasses and landed on his eye, he said.

“I freaked out,” he said. “I whip off my sunglasses and my kids are freaking out wondering why their dad is freaking out.”

But he added that the incident was perhaps good for a bunch of urban families.

“I do love a bunch of city kids experiencing nature. Because you rarely see anything like that at that volume,” Koutsky said.

Repeat Of Past Infestations?

What were thought to be June beetle grubs previously plagued Welles Park in 2021 , devastating about a third of the popular park’s 15 acres when, after heavy rains, they emerged and died in muddy pools.

Despite the Park District previously using an insecticide called Dylox to eliminate the grubs, they returned this spring to again damage the eastern side of the park.

After the latest instance of grub damage earlier this year the district closed off access to the fields and contracted Christy Webber Landscapes to reseed them. The landscaper did not immediately respond to a request for comment.

A Park District spokesperson also could not immediately be reached Monday.

Some of the beetles Block Club Chicago observed on the eastern side of Welles Park the afternoon of July 6, 2026. Credit: Alex V. Hernandez/Block Club Chicago

To break up the beetles’ lifecycle, Dietrich recommends improving the quality and health of the turf grass by seeding over its bare spots, mowing frequently and avoiding over-watering, he said.

Park officials could also let nature run its course by allowing natural enemies — like parasitic wasps and other naturally occurring pathogens — build up their populations naturally and eventually cull the beetle population, he said.

Another option is using commercial pheromone traps to capture and kill adult males, which can disrupt mating and result in fewer eggs being laid, he said.

“I’ve heard that home-made bait traps containing rotting fruit actually work better by capturing both males and females,” Dietrich said.

Other options include treating Welles Park’s soil in late summer with a non-chemical insecticide formulation that contains parasitic nematodes, which can be purchased commercially and are an environmentally friendly way to help control the grub infestation he said. Milky spores, “a kind of fungus that is parasitic on beetle grubs,” he said “doesn’t seem to work very well.”

Chemical insecticides are likely the most reliable option if the Park District is looking to eradicate the population quickly as long as it’s rated for use on June beetles, he said.

“But the available chemical treatments often negatively impact natural enemies like parasitic wasps and predators, as well as beneficial insects such as pollinators,” Dietrich said.