Millions of buried creatures burst forth each spring from beneath the soil of a cemetery in Ithaca, New York.
It's not the return of the living dead; it's one of the world's largest aggregations of ground-nesting bees, ravenous for pollen.
Entomologists at Cornell University estimate that East Lawn Cemetery is home to around 5.5 million individual regular miner bees (Andrena regularis), a species that does not live in a colonial hive, as honeybees do, but instead spends most of its life in solitude in underground burrows.
And though A. regularis was already a known inhabitant of the cemetery, with records of the species' presence dating back to 1935, it wasn't until 2021 that the full scale of this nearby bee aggregation became apparent.
Rachel Fordyce, a technician at a Cornell entomology lab, discovered the massive nesting aggregation after finding a sneaky free parking spot a few blocks from campus.
While crossing the cemetery grounds on her way to work one spring day, she was able to capture a jarful of bees to show her colleagues that this site might be worth checking out.
In New York, A. regularis emerges from the ground around April each year to eat pollen, mate, and, for females, to dig brood burrows in which their larvae, well-stocked with pollen and nectar, can spend the winter growing in preparation for next spring's flight.
"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," says biologist and the paper's first author Steve Hoge, a Cornell undergraduate student at the time of the research.
The research team began fieldwork in the spring of 2023, setting up 10 emergence traps: tents measuring 36 square centimeters (5.6 square inches), open at the bottom, placed over the bees' nests, which funnel insects into a plastic collection jar, trapping them in 70 percent ethanol.
Each collection jar provided a small snapshot of the ecosystem, from which the entomologists could extrapolate. They collected these emergence samples over 48 days, yielding a total of 3,251 insects from 16 species.
Bee density varied widely between traps, and extrapolations from small datasets are always an imperfect way of gauging population size.
Nonetheless, this field survey suggests the East Lawn Cemetery has an average of 853 A. regularis bees nesting in every square meter (10.8 square feet) of its sandy loam soil.
Which means that as many as 5.56 million bees could have emerged from the site in the spring of 2023.
"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," says Hoge.
A. regularis was, by far, the most abundant species at the site, but these bees don't have full run of the plot; they have plenty of neighbors. One of them is the 'cuckoo' bee Nomada imbricata, a species that happens to be A. regularis's most common brood parasite.
"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," says Cornell entomologist Bryan Danforth.
These bees' contribution to the local economy is nothing to scoff at. A. regularis is a known pollinator of apples and blueberries. Previous research has shown these bees contribute greatly to the pollination of New York's iconic apples.
A cemetery may seem a grim place for these harbingers of springtime, but it's actually a pretty ideal location for ground-nesting species like A. regularis.
"The peacefulness, the lack of pesticides, and the fact that, overall, the ground is rarely disturbed, all make cemeteries good habitat for bees," Danforth says.
The majority of bee species are ground-nesting – 75 percent – but relatively little is known about them, no doubt in part due to their reclusive lifestyles.
Danforth and the team are concerned that many more aggregations of bees, like the East Lawn Cemetery population, could be overlooked and at risk.
"These populations are huge, and they need protection," Danforth says. "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."
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Out of this research, Danforth and team have established a global community science project to encourage people around the world to take notice of, and record, their local ground-dwelling bees.
The research was published in Apidologie.