Ancient wasp may have used its rear end to trap flies

Amber Fossil Reveals Bizarre Trap-Jaw Wasp from the Cretaceous Period

Scientists have identified an extinct wasp preserved in amber exhibiting an unusual anatomical feature: a specialized abdominal structure. This newly discovered fossil insect appears to have utilized its abdomen to seize prey, similar to a Venus flytrap, before depositing eggs. The remarkable find offers novel insights into the diversity of parasitoid wasp behavior during the Cretaceous period.

Unique Morphology of Sirenobethylus charybdis

Lars Vilhelmsen, a researcher at the Natural History Museum of Denmark, described the discovery as unprecedented. “It’s truly unlike anything I’ve ever encountered. It defies comparison with any known wasp or insect species existing today,” he stated.

Vilhelmsen and his team have classified the wasp as Sirenobethylus charybdis, drawing inspiration from Charybdis, the monstrous whirlpool in Homer’s epic, The Odyssey. This creature inhabited Earth approximately 99 million years ago during the Cretaceous period.

Micro-CT Scans Uncover Abdominal Clasping Mechanism

The research team employed micro-CT scanning, an advanced X-ray imaging technique, to meticulously examine 16 female wasps encased within amber. The amber specimens were unearthed in the Kachin region of Myanmar.

Analysis revealed that all specimens possessed three distinct flaps within their abdomens, forming a discernible grasping abdomen structure. The structure’s varied positions – sometimes extended, sometimes partially retracted – indicated it was a dynamic, prehensile apparatus during the insect’s lifetime.

“The discovery was incredibly exciting, yet it presented a significant challenge,” Vilhelmsen explained. “How do we elucidate the function of this animal when there is no contemporary analogue?”

Drawing Parallels to Modern Parasitoid Wasps

To unravel the mystery, the scientists compared the fossilized wasps to both extant and extinct wasp species, analyzing their characteristics. This comparative study suggested that the closest living relatives to the amber wasps are modern parasitoid wasps belonging to the superfamily Chrysidoidea. This group includes cuckoo wasps, whose larvae develop as parasites within host organisms, ultimately causing their demise as they consume them.

Venus Flytrap Analogy for Prey Capture

The pivotal element in understanding S. charybdis’s behavior may reside in the lower flap of its trap-like abdomen, which Vilhelmsen likens to a Venus flytrap. “Extending from this lower flap are fan-shaped, elongated trigger hairs, presumably sensory in nature. It’s plausible that if this flap rested on a surface and a potential host traversed nearby, contact with these hairs would trigger a rapid, backward lunge by the wasp towards the perceived host,” he proposed.

Vilhelmsen postulates that S. charybdis likely adopted an ambush predation strategy, lying in wait for vulnerable prey such as flying insects or jumping nymphs. With its abdominal trap open, it would swiftly snap it closed to immobilize its victim, enabling oviposition.

A Novel Parasitic Strategy

Manuel Brazidec, a researcher at the University of Rennes in France, hailed the discovery as “genuinely unique.” He emphasized, “The truly remarkable aspect is that the abdomen of Sirenobethylus charybdis represents an entirely new evolutionary solution to a universal challenge faced by parasitoid insects: effectively restraining a host organism to facilitate egg-laying.”