Some 99 million years ago, female potter wasps in what is now Myanmar were building bottle-shaped mud nests, laying eggs inside them and sealing them up — behaviors that mirror exactly what their modern descendants do today.
The researchers report January 5 in Current Biology that the oldest known potter wasp nests, preserved in amber, indicate that potter wasps’ nesting strategies were already fully developed by the mid-Cretaceous period. The fossils push back the timeline for these sophisticated behaviors in potter wasps, a group within the stinging Hymenoptera known for their solitary lifestyles and careful brood care.
“These nests exhibit striking morphological similarities to those of the extant species of the tribe Eumenini, including bottle-shaped architecture, mud-based construction, and preserved eggs, demonstrating that nesting behaviors had already evolved by the Cenomanian,” the researchers write.
A close-up view of amber containing two adjacent bottle-shaped chambers with rough surfaces and an egg inside one
Fossilized potter wasp nests in Kachin amber, showing bottle-shaped chambers and a preserved egg. The nests date to about 99 million years ago.
The nests were found in Kachin amber from northern Myanmar, dated to around 98.79 million years old. Two connected chambers appear in a single piece of amber, likely built by one female wasp, as these insects construct cells one after another. Each chamber is bottle-shaped with thick walls, about 14 to 18 millimeters tall, and has a rough outer texture from mud particles — features that match those of living Eumenini potter wasps.
Inside one chamber, the team spotted an oval egg, about 3.2 by 3.8 millimeters, attached to the lower inner wall. This placement and the fact that the egg was laid before any food was added for the larva set it apart from other wasp families and confirm it’s from a potter wasp.
“The absence of provisions and the complete closure of the egg (unbroken chorion) indicates that the eggs were entombed prior to hatching and before the adult female had returned to the nests to provide food for her brood, conclusively identifying the nest, along with its other architectural features, as that of a eumenine,” the study states.
The grey base of the nests suggests they were attached to a solid surface, like a rock or branch, much like how modern potter wasps choose sheltered spots to protect against drying out, predators, or weather changes.
Adult potter wasps had been found in Cretaceous amber before, but these are the first nests from that era, making them older than known body fossils by about nine million years. They offer a rare glimpse into ancient insect behavior through trace fossils, rather than just bones or bodies.
“The architectural continuity between these 99-million-year-old nests and modern Eumeninae demonstrates remarkable evolutionary stability in nest-building techniques,” the researchers note.
Citations
S. Wang, C. Shi et al. Potter wasp nests in Cretaceous amber. Current Biology. Published online January 5, 2025. DOI: 10.1016/j.cub.2025.11.019
