Researchers have uncovered the first-ever evidence of ancient bees nesting inside fossilized animal bones within a Caribbean cave, a discovery that fundamentally challenges our understanding of insect behavior and adaptation over millennia.
The discovery, published in the journal Royal Society Open Science, represents a never-before-seen behavior in the insect world and provides a rare glimpse into the nesting habits of ancient bees. The findings were made in a limestone cave on the island of Hispaniola, where researchers found tiny bee nests meticulously constructed within the empty tooth sockets of fossilized bones.
The Significance of Solitary Bee Behavior
Contrary to the common image of large, social honeybee hives, approximately 90% of bee species are solitary, typically building nests in the ground, rotting wood, or plant stems. This discovery dramatically expands our understanding of where these solitary bees might establish their nests.
Lead researcher Lázaro Viñola-López, a postdoctoral researcher at the Field Museum of Natural History in Chicago, described the finding as particularly surprising given the cave environment. “You never find invertebrates there—you find snails, but you don’t find insects,” Viñola-López noted. “Usually what you find in this cave are rodents, birds, like all that fauna. So finding evidence of ancient bees in those cave deposits was very exciting.”
A Rare Glimpse into Ancient Ecosystems
The research team believes the fossils housing these bee nests date back approximately 20,000 years, filling a significant gap in the Caribbean fossil record. All other bee fossils described in the region were discovered within amber and are much older, dating back around 20 million years.
The cave itself contains layer upon layer of fossils from more than 50 species, including rodents, birds, and reptiles. The study authors believe a family of barn owls once lived in the cave and coughed up the bones of their prey, which eventually fossilized. Other species, such as tortoises and crocodiles, may have fallen into the cave—which has an approximately 8-meter drop at its entrance—and died when unable to climb back out.
Scientific Analysis Reveals Bee Architecture
Using CT scans and X-ray technology that creates detailed 3D imaging, researchers determined that the small nests were made of mud and belonged to bees rather than wasps. While wasp nests are typically made from a mix of saliva and chewed plant fibers, these nests were smooth on the inside—indicative of a bee’s nest-building process, which uses compacted dirt and a secreted waxy substance that coats the interior walls.
“This is a very interesting record because usually for bees, sometimes they like shaded areas, some of them can be nocturnal, but nesting in a cave is a very, very strange behavior,” Viñola-López explained. There is only one other recorded instance of a burrowing bee nesting inside a cave.
Communal Nesting and Scientific Classification
The discovery suggests this was not an isolated incident. “We also know that it is not one specimen that did it,” Viñola-López said. “Even in a single hole of a mandible, there are up to six generations of bees coming back to that same single hole. So it seems that it was probably a large communal nesting.”
Despite the well-preserved nests, the muggy cave conditions were not ideal for preserving the actual insect bodies. Researchers were therefore unable to determine which species of bee built these nests or whether they represent an extinct species or one still existing today. The nests themselves have been classified as Osnidum almontei, named after Juan Almonte Milan, the scientist who first discovered the cave.
Expert Perspectives on the Discovery
Stephen Hasiotis, a geology professor at the University of Kansas, Lawrence, whose research focuses on paleontology and ichnology (the study of trace fossils), noted that this discovery adds to the record of “hidden biodiversity.” Although no body fossils of bees were recovered from the cave, their trace fossils are diagnostic of soil bees and provide valuable information about their environment and ecosystem.
“The bees likely built their nests in the cave soils because the humidity within the cave and soils would have been nearly constant,” Hasiotis explained. “The area was likely protected from heavy rains and floodings, not to mention also being protected from many potential predators and omnivores of various sizes cohabiting the soils in which they burrowed.”
Anthony Martin, a professor of practice in the department of environmental sciences at Emory University in Atlanta and author of “Life Sculpted: Tales of the Animals, Plants, and Fungi that Drill, Break, and Scrape to Shape Earth,” called the discovery “doubly surprising.”
“Modern bees aren’t known to use bones for their nesting, nor are they known to nest in caves,” Martin said. “But these fossil bee brooding chambers in sediment-filled parts of bones tell us that their makers could do both, which is exciting to know.”
Martin added: “Insects have been adapting to changes in their environments for almost 400 million years, and ground-nesting bees have been around for about the last 100 million years of that time. This exciting fossil discovery serves as a good reminder that when it comes to evolution, bees will keep on being the bees they need to be.”
Implications for Future Research
This discovery has significant implications for our understanding of bee behavior and adaptation. It demonstrates that the diversity of nesting processes among bees is far greater than previously understood and expands beyond what scientists considered normal behavior.
Viñola-López emphasized that researchers must look closer at specimens for all the things that can get preserved inside them, as these can reveal very strange behaviors of species that we thought we understood relatively well. He hopes to return to the area to conduct further surveys that may help determine whether the bees are still in the area and if this behavior is found in other caves and on other islands.
The full research detailing this extraordinary discovery is available in Royal Society Open Science.
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