A new study from Cornell University in the United States shows that under a historic cemetery in Ithaca, New York, there are about 5.5 million wild bees nesting in underground chambers. It is considered to be one of the largest and oldest ground-nesting bee colonies currently documented. The discovery highlights the important role of wild pollinators in agricultural production and ecosystems, and sparks discussion about how "non-traditional green spaces" such as cemeteries can serve as biodiversity refuges in cities.
This research originated from an accidental observation. In the spring of 2022, Rachel Fordyce, an entomology laboratory technician at Cornell University’s College of Agriculture and Life Sciences, often parked her car near Ithaca’s East Hill Plaza in order to save parking fees, and then walked to work through the East Lawn Cemetery next to it. One day, she walked into the laboratory with a specimen bottle full of bees and told her instructor, Professor Bryan Danforth: "These bees are all over the cemetery." After identification, these insects were Andrena regularis, commonly known as "regular mining bees", which are solitary, ground-nesting wild pollinator bees.
Further investigation revealed that the colony beneath the cemetery was much larger than the research team expected. Researchers estimate that there are at least about 5.5 million regular ground bees here, forming high-density nests in an area of about 1.5 acres (about 6,000 square meters). Calculated by the number of colonies, this is equivalent to more than 200 boxes of bees in traditional beehives concentrated in a small area, a total of more than three times the population of Manhattan. Steve Hoge, the first author of the research paper and an undergraduate student in Danforth's research group, said that although there may be unrecorded very large bee colonies in the world, this cemetery colony "is one of the largest known" in terms of published scientific literature.
The regular ground bee has important economic value in local agricultural production. The latest research published in the journal "Apidologie" used this cemetery bee colony system to record the biological characteristics of this often overlooked wild bee, and proposed a new set of methods for recording bee biology. The study emphasizes that wild bees, represented by the regular bees, play a key role in pollinating high-value cash crops such as apples, one of the most important agricultural products in New York State. Danforth said the study "raises the profile of solitary nesting bees, demonstrating their large numbers, importance as crop pollinators, and the need to identify and protect these nest sites."
Historical records indicate that the presence of regular ground bees in East Lawn Cemetery dates to the early 20th century, and the cemetery itself was established in 1878. The findings support the idea that old cemeteries are important habitats for urban wildlife. Cemetery superintendent Keven Morse said he has seen a variety of wildlife in the park over the years, including deer, nesting geese, hawks, foxes and coyotes. Bees have also been active here, but they have never stung him. He admitted that in the three or four areas where the density of bees is particularly high, "it's a bit unbearable every time I have to mow the grass."
The scientific research team believes that it is no accident that the cemetery has become a "safe haven" for large bee colonies. Danforth explained that the cemetery's relatively quiet environment, low human disturbance, no pesticides, and minimal soil disturbance combine to create an ideal habitat for ground-nesting bees. The Cornell Orchard, about one-third of a mile from the cemetery, provides a rich source of flowers in early spring, and the sandy soil where the cemetery is located is the preferred nesting substrate of regular ground bees. These two aspects are likely to support the long-term existence of this very large colony.
Regular ground bees belong to the solitary ground-nesting bees and account for a very high proportion of bees in the world, but their research has been relatively weak for a long time. Currently, about 75% of bee species adopt a solitary, ground-nesting lifestyle, but it is far less well-known than social bees and bumble bees. Hogg recalled that when he started the project, he found that a more systematic scientific description of the regular ground bee dates back to 1978, and since then the relevant biological information has been very limited.
According to new research, female regular wasps dig nests underground, build a series of brood chambers, and store pollen and nectar in them for their larvae to develop. The eggs hatch into larvae underground, then molt and develop, eventually emerging as adults below the surface. A distinctive feature of this species is "overwintering in adult form", which is relatively rare among bees. Hogg pointed out that this is one of the reasons why regular ground bees can be the first to emerge in early spring when honey source tree species bloom, including apple trees, other fruit trees and early spring blooming wildflowers. In New York, local rule bees typically emerge from their nests in April and are most active when daytime temperatures are near 21 degrees Celsius (70 degrees Fahrenheit).
In order to systematically evaluate bee colony size and species composition in the habitat, the research team designed an "out-of-nest trap" monitoring method. They built a small mesh-like cage above less than one square meter of ground to guide insects emerging from the ground into collection containers. Danforth explains that this method is able to "capture an entire community of animals emerging from a small area of the surface in one go." From March 30 to May 16, 2023, the team set up a total of 10 out-of-nest traps and collected a total of 3251 insects, covering 16 species such as bees, flies and beetles, among which the regular ground bee was the absolute dominant species.
The researchers calculated the bee colony density per unit area based on the number of regular ground bees recorded in each trap, and then extrapolated it to the total area of the cemetery of about 6,000 square meters. They then estimated that the size of the bee colony under the cemetery surface ranged from 3 million to 8 million, with an average of about 5.5 million. Monitoring data shows that male bees emerge first during the warmer months of April, while female bees emerge intensively a few days later. Hogg pointed out that “the male bees leave the nest first and wait for the female bees on the ground. This can maximize the chance of mating and pass on their genes.” This pattern is consistent with observations of other early spring bee species.
Out-of-nest traps also reveal the complex parasitic relationships within cemetery nest colonies. The study documented that the wandering bee Nomada imbricata, also known as the "cuckoo bee", appears late in the hive of regular bees and lays eggs in the latter's cells. After the bee larvae hatch, they will kill the host larvae and consume the pollen resources in the nest that originally belonged to the host. This “parasitic brooding” strategy further demonstrates the multi-layered interactions of the cemetery’s underground ecosystem.
To expand public awareness of and engagement with the group, Danforth and colleagues launched a global citizen science initiative that encourages the public to submit sightings and images of geoswarming bees and their colonies through a website. The research team emphasized that many similar bee colonies are large in scale but lack adequate protection. Once their nesting sites are covered by roads or buildings, millions of individual bees that are crucial for crop pollination may disappear in an instant. Danforth called for, "These populations are staggering in size and urgently need protection. If these nest sites are not maintained and someone pours cement on them, we may lose 5.5 million important pollinator bees overnight."