Fossils suggest the insect laid eggs in the smaller creatures that got caught in the trap
Ancient Wasp Trapped Prey Using Rear-End “Mouth,” Fossils Reveal
Roughly 99 million years ago, a now-extinct wasp species evolved a truly bizarre hunting adaptation — a rear-end appendage resembling a mouth, used to trap prey. New fossil evidence suggests this ancient insect may have captured its victims using flaps on its abdomen, much like the snapping jaws of a Venus flytrap.
“At first glance — the head, thorax, even the wings — it looks like your average wasp,” says insect specialist Lars Vilhelmsen. “But the abdomen tells a completely different story.”
Unlike the pointed, rounded abdomens common among modern stinging wasps like yellow jackets, this prehistoric species had a strange multi-flap structure. The overlapping segments on its abdomen closely resemble the trapping leaves of a carnivorous plant.
Vilhelmsen and colleagues published their discovery in the journal BMC Biology on March 27. He is based at the Natural History Museum of Denmark, part of the University of Copenhagen.
Trapped in Amber, Preserved in Time
Working with researchers from Capital Normal University in Beijing, Vilhelmsen examined 16 fossilized wasps recovered from amber deposits in northern Myanmar. The clarity of the amber preserved minute details — enough to spot the wasp’s unusual body structure.
Initially, Vilhelmsen thought the strange abdominal shape might be an illusion, perhaps caused by a bubble or deformity in the amber. But CT scans confirmed that the flaps were real anatomical features.
Entomologist Anderson Lepeco, who wasn’t part of the study, was equally stunned. “I’d never seen anything like it,” says Lepeco, based at the University of São Paulo in Brazil. His first thought was that the wasp had a deformity — until he realized all the specimens shared the same unique body structure.
“That’s when I knew we were looking at something genuinely fascinating,” he says.
A Mythical Namesake
The researchers named the wasp S. charybdis, after the Greek sea monster Charybdis — often depicted with a gaping, toothy maw. The wasp’s abdomen, which opens and closes like a jaw, inspired the comparison.
Its abdomen is composed of three articulated flaps — upper, middle, and lower. In some specimens, the lower flap is seen spread wide open; in others, it lies flush with the rest, suggesting mobility. The researchers believe the structure functioned to grasp prey.
Adding to the intrigue, the lower flap bristles with fine hairs. These may have served a sensory function, triggering the flap to snap shut when brushed — echoing how Venus flytraps trap insects with similar hair-based triggers.
A Predator with a Purpose
Most predators catch prey to eat it. But for this wasp, the goal may have been reproduction. The strange abdominal structure is located closer to its egg-laying organ (ovipositor) than to its mouth, leading scientists to suspect it was used to hold other insects still while the wasp deposited eggs onto — or into — them.
“It makes sense,” says Lepeco. “All members of this group are parasitoids.”
Parasitoid insects lay their eggs in or on other animals. When the larvae hatch, they feed on the living host. Lepeco studies parasitoids that use venomous stingers to immobilize prey before laying eggs. He speculates that S. charybdis may have used its abdominal trap to achieve a similar end — securing the host long enough to reproduce.
Scott Shaw, an entomologist at the University of Wyoming, agrees. While the fossil record can’t confirm behavior, the anatomical features strongly suggest the wasp’s abdomen was adapted for restraint, not consumption. “It’s probably how the species laid eggs on other insects,” he says, “but of course, we can’t observe it directly.”
Still, Lepeco is amazed such a structure even existed. “We often marvel at extinct giants like dinosaurs,” he notes, “but insects of the past were just as extraordinary in their own ways.”