5.5M ground nesting bees make home in Ithaca cemetery

To save money, Rachel Fordyce parked her car for free at Ithaca's East Hill Plaza and walked through East Lawn Cemetery to her job as a technician in an entomology lab on Cornell's campus. One spring day in 2022, she walked in to work with a jar full of bees.

"These are all over the cemetery," she told her boss, Bryan Danforth, professor of entomology in the College and Agriculture and Life Sciences. They identified the bees as Andrena regularis (also known as the "regular mining bee"), a wild, solitary, ground-nesting species that is an important pollinator.

Fordyce's jar of bees led to the discovery that the Ithaca cemetery is home to one of the largest and oldest recorded aggregations of ground nesting bees in the world, with an estimated 5.5 million individual bees. That's the equivalent of more than 200 honeybee hives in a 1.5-acre plot of land, and more than three times the population of Manhattan.

"I'm sure there are other large bee aggregations that exist around the world that we just haven't identified, but in terms of what is in the literature, this is one of the largest," said Steve Hoge '24, first author of a new study published April 13 in the journal Apidologie. The research delves into the biology of these economically important but understudied wild bees, using those at East Lawn Cemetery as a case study. Hoge conducted the research as an undergraduate working in Danforth's lab .

The paper describes a novel method for documenting many aspects of bee biology, reveals how such wild bees are extremely important agricultural pollinators for high-value specialty crops, such as the apples, one of New York's most iconic and valuable commodities, and points to the importance of cemeteries as preserves of biological diversity.

"The research elevates the value of solitary ground-nesting bees and shows just how abundant these bees are, how important they are as crop pollinators, and that we need to be aware of these nest sites and preserve them," Danforth said.

Historical bee observation data revealed that A. regularis has been collected in the East Lawn Cemetery as far back as the early 1900s; the cemetery itself was founded in 1878.

The discovery adds credence to claims that cemeteries serve as preserves of biodiversity. Older cemeteries, particularly in urban centers in Europe, are known to be refuges for rare plants, insects, birds and mammals. Indeed, Keven Morse, East Lawn Cemetery's superintendent, whose family has been involved with the private nonprofit business for the last 46 years, said he has observed deer, nesting geese, hawks, foxes and coyotes on the grounds. And of course, bees, which he said have never stung him. "I just felt bad having to mow in certain areas," he said. "There's probably three or four sections where they really migrate heavy, there's a lot of them."

The peacefulness, the lack of pesticides and the fact that, overall, the ground is rarely disturbed, all make cemeteries good habitat for bees, Danforth said.

A. regularis and other ground nesting bees are vastly understudied, even though 75% of bees are solitary ground nesters. "It's the most common lifestyle for bees," Danforth said. When Hoge began the study, he searched the scientific literature for information on A. regularis and found the most comprehensive and useful article dated back to 1978, which created an opportunity to more fully describe the bee's biology.

Like most solitary, ground-nesting bees, female A. regularis dig subterranean nests and lay eggs in brood cells provisioned with pollen and nectar. The eggs hatch into larvae and develop into adults underground.

"This species overwinters as adults, which is relatively rare, and that's part of the reason why they come up out of the ground so early in the spring, timed to the apple bloom," as well as other fruit trees and early blooming wildflowers, said Hoge, who majored in biology and society in the College of Arts and Sciences and is now a research assistant in the Division of Renal Medicine, Brigham and Women's Hospital at Harvard, with plans to attend medical school in the fall. In New York, A. regularis emerges around April, when temperatures begin to regularly hit 70 degrees at midday.

Cornell Orchards, around one-third of a mile away, provides a large resource of blooming flowers in early spring. This might partly explain the cemetery's enormous population of A. regularis, along with the area's sandy soil, which these bees prefer, Danforth said.

In the study, the authors applied a new method to measure population size and to understand sex ratios and the timing of when males and females emerge from the ground in spring. They employed emergence traps, which are small mesh tents that are open on the bottom and sit over less than a square meter of ground. A funnel leads to a glass jar that traps insects.

"You capture a whole community of animals coming out of the ground with this approach," Danforth said.

The team set 10 traps between March 30 and May 16, 2023. They collected 3,251 individuals representing 16 species of bees, flies and beetles, with A. regularis as the dominant species, according to the paper.

By counting how many bees were caught in each trap, the team calculated average bee density, or the number of bees emerging from a square meter of ground. Researchers then extrapolated that number to the total area of the cemetery, about 6,000 square meters. Given that different traps captured different numbers of bees, they calculated that the total population of A. regularis ranged from as few as 3 million to as many as 8 million, with an average of 5.5 million total bees.

The traps revealed that the males emerge first in bursts of activity when the weather warms in April. Days later, the females emerge. "The males come out first and wait for the females, so that they have the best opportunities to mate and pass on their genes," Hoge said, confirming that A. regularis follows a pattern noted in other early spring bee species.

The traps also allowed the team to identify and confirm brood parasitism by nomad (or "cuckoo") bees (Nomada imbricata), which emerge later than A. regularis and at a slower rate, as they wait for the ground bees to provision their brood cells. They then lay their eggs in the brood cells of A. regularis. The nomad's larva kills the larva of their miner bee host, and then feed on the pollen and provisions in the cell.

Danforth and the team have created a global ground-nesting bee citizen science project, where people around the world can report on ground nesting bees and aggregations they observe in their daily lives.

"These populations are huge, and they need protection," Danforth said. "If we don't preserve nest sites, and someone paves over them, we could lose in an instant 5.5 million bees that are important pollinators."

Co-authors include postdoctoral researchers Jordan Kueneman and Katherine Odanaka, undergraduate students Steve Hoge '24 and Cassidy Dobler '26, and lab technician Rachel Fordyce.

The study was funded by the Cornell Atkinson Center for Sustainability, the National Science Foundation, and the Federal Capacity Funds program.