Five years ago, hundreds of digger bees were nesting beneath the Interstate 78 bridge over the Schuylkill River in northern Berks County.

The coal silt on the southern-facing bank beneath the bridge in Tilden Township was ideal for the tiny rare bees to do what they do best: dig tunnels.

The bees do not sting. When the sun comes out in the afternoon, they pollinate plants and flowers.

It was a comfy place to nest — until last summer when construction crews were getting back to work on a $125.4 million project that includes widening the bridge to three lanes in both directions.

So, the bees got the message: time to go. 

Mike Slater, an entomologist, knew just what to do: Bring the bees to his Brecknock Township home in 18 plastic foam boxes to rest. 

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Mike Slater with some of the trays of digger bees

"There are only a half-dozen of these bee colonies in Pennsylvania," Slater said recently. "They only fly for a month, and they dig tunnels."

2025 homecoming? 

Slater researched the process, contacting bee researchers worldwide. He even met with PennDOT engineers and others to discuss his plan and got PennDOT's permission to rescue the bees, also known as ground bees.

The move became part of PennDOT's bridge contract with J.D. Eckman Inc., Atglen, Chester County. The contractor provided the mulch.

Now, Slater is getting ready for a second move. He plans to relocate the bees to a pavilion in Robeson Township in May so they have more room to dig.

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PennDOT crews protected the area where rare digger bees were found under an Interstate 78 bridge in Tilden Township during a $125.4 million construction project.

If all goes as planned, the bees will be back under the bridge by December 2025, when the bridge construction is over.

"Hopefully there will be a population of digger bees back under the bridge after the highway project is complete," said Ronald J. Young, spokesman for PennDOT's District 5, which includes Berks County. 

Young said the state Department of Conservation and Natural Resources notified PennDOT about the bees under the bridge when the construction project began last spring.

Young said the digger bees are listed as state endangered species because there are so few of them, but have no regulatory protection, which means PennDOT could have done nothing to avoid or mitigate any impact. 

Instead, PennDOT worked with Blue Mountain Wildlife and Slater to save the bees.

During the I-78 project's design, PennDOT staff fenced the area to keep the nesting site from being impacted. 

They installed plastic foam nesting boxes under the bridge — and the bees migrated to the boxes — with the same habitat temporarily until they were moved to Slater’s garage. 

PennDOT also made the nesting area off limits to the contractor for the first three months of construction to allow nesting boxes to be used by the bees and then relocated to another habitat. 

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Mike Slater holds one of the trays with digger bees in it. At the home of entomologist Mike Slater in Brecknock Township Thursday afternoon January 28, 2021 where he is storing Digger Bees that he moved from under an I-78 bridge to prevent them from being disrupted during construction.

When the nesting boxes were transported to Slater's house, the contractor began work in that area. 

"PennDOT staff will work with the entomologist after construction to repatriate the original site with the digger bees," Young said. 

'Friendly bees'

For Slater, that day can't come soon enough.

He first learned about the bees about five years ago from a hiker he met while looking for dragonflies near the bridge.

Slater said he saw about a thousand bees flying near the bridge.

Slater and Kerry Grim, a volunteer with Blue Mountain Wildlife, later came up with a plan to relocate the bees. Blue Mountain leases the land along the Schuylkill River from the state for $1 a year.

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Digger Bees in their prepupa state. At the home of entomologist Mike Slater in Brecknock Township Thursday afternoon January 28, 2021 where he is storing Digger Bees that he moved from under an I-78 bridge to prevent them from being disrupted during construction.

Greg Adams, director of Blue Mountain Wildlife, said the bees like to dig into the soil on the banks under the bridge. The area where the bees were nesting is part of Kernsville Recreation Area in Tilden Township.

Adams learned a lot about the bees from Slater.

"They are friendly bees," he said. "I think they like the coal silt. It's easy for the bees to dig in. These bees are cool creatures. They like to pollinate flowers. They aren't something you see anywhere else in the area."

Adams said the contractors were cognizant of what was going on around them with the bees.

"PennDOT was very helpful," Adams said. "Bridges can provide a place for wildlife near water."

Adams said people become interested when you talk to them about how rare the bees are.

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