Parasitic wasp had a 'flytrap' for snatching its victims

A newly discovered species of parasitic wasp that lived alongside dinosaurs nearly 100 million years ago may have evolved a bizarre and highly specialized mechanism to trap other insects and turn them into unsuspecting incubators for its offspring. 

Preserved in amber, the wasp appears to have used a Venus flytrap-like structure on its body to grasp potential hosts, offering scientists a fascinating glimpse into prehistoric parasitic behavior.

Parasitic wasp like no other

The species, Sirenobethylus charybdis, was identified from 16 remarkably preserved specimens found in Cretaceous-period amber from Myanmar’s Kachin region. The research describes a novel grasping appendage located on the abdomen of the female wasps.

“When I looked at the first specimen, I noticed this expansion at the tip of the abdomen, and I thought this must be an air bubble. It’s quite often you see air bubbles around specimens in amber,” said Lars Vilhelmsen, study co-author and a curator at the Natural History Museum of Denmark. 

“But then I looked at a few more specimens and then went back to the first one. This was actually part of the animal.”

The structure’s purpose quickly intrigued the research team, especially once they observed its mobility across different specimens.

“Sometimes the lower flap, as we call it, is open, and sometimes it’s closed,” Vilhelmsen said. “It was clearly a movable structure and something that was used to grasp something.”

Ancient wasp like a Venus flytrap

While nothing quite like this structure exists among modern insects, the researchers found the best comparison in an entirely different kingdom: the Venus flytrap. 

“There’s no way you can know how an insect that died 100 million years ago was living. So you look for analogs in modern insect fauna. Do we have anything among wasps or other groups that looks like this?” Vilhelmsen said. 

“And there’s no real analog within insects. We had to go all the way out of the animal kingdom into the plant kingdom to find something that remotely resembled this.”

Although the structure resembles a predator’s trap, the team believes it was not used to kill. Instead, they propose that the wasp used it to seize other insects just long enough to lay eggs into their bodies. 

Once released, the unwitting hosts would carry the wasp larvae, which would eventually consume them from the inside out. According to Vilhelmsen, the likely hosts were flying insects of similar size.

A window into ancient parasitism

Modern parasitoid wasps engage in comparable reproductive strategies. For instance, cuckoo wasps lay their eggs in the nests of other species, leaving their offspring to feed on the host’s young. 

Yet the unique abdominal trapping mechanism seen in Sirenobethylus charybdis has no true parallel in living insects, adding to its mystery.

The amber in which the fossils were preserved provided an exceptionally detailed view of the wasp’s anatomy. In addition to Sirenobethylus charybdis, other remarkable finds from Myanmar amber have included everything from dinosaur tails and ancient spiders to crab and ant fossils. 

The specimen of this wasp was purchased by a fossil collector and later donated to Capital Normal University’s Key Laboratory of Insect Evolution and Environmental Changes in 2016.

However, the use of Myanmar amber in scientific research has become controversial in recent years due to ethical concerns surrounding the country’s political instability and military conflicts.

Some paleontologists have called for a halt on studying these specimens until issues around their provenance and trade are resolved.

Speculation over the wasp’s flytrap

The peculiar form and function of Sirenobethylus charybdis has captured the attention of entomologists and paleontologists alike. Phil Barden, an associate professor at the New Jersey Institute of Technology who studies amber fossils, described the wasp as a “Cretaceous weirdo.” 

“This is significant because there are around a million known insect species – even with all of that living diversity, there are still lots of unexpected surprises in the fossil record that are beyond imagination,” he said.

While Barden acknowledges the wasp flytrap hypothesis as “plausible,” he also expressed caution, noting it remains speculative. 

“There appears to be clear evidence that the abdominal components would have had range of motion. There are also a number of setae, or hairs, that look to be in the right position to detect hosts and potentially immobilize them.” 

Still, Barden suggested alternative possibilities, such as using the structure to sense prey in the soil or even to transport young wasps.

He also questioned why Sirenobethylus charybdis would need such a structure at all when many living parasitoid wasps rely solely on stingers or mouthparts to capture and manipulate hosts. This makes the discovery all the more intriguing.

Unanswered questions and new possibilities

Vilhelmsen and his team believe a key clue lies in the wasp’s reproductive anatomy. The egg-laying organ, or ovipositor, is located directly adjacent to the clasping structure, supporting the theory that the mechanism was used during reproduction. 

Yet all the known specimens are female, so scientists can’t rule out other functions, such as roles in mating.

“This is something unique, something I never expected to see, and something I couldn’t even imagine would be found,” Vilhelmsen said. “It’s a 10 out of 10.”

With every amber discovery, paleontologists inch closer to understanding the rich complexity of ancient ecosystems. And sometimes, as in the case of Sirenobethylus charybdis, they uncover something so strange and unexpected it defies comparison even among the millions of species alive today.

The study is published in the journal BMC Biology.

Image Credit: Qiong Wu

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