Scientists discovered of a previously unknown species of wasp preserved in 99-million-year-old amber from the Kachin region of northern Myanmar. The findings were reported in a study published in the scientific journal BMC Biology.
The ancient wasp, named Sirenobethylus charybdis, lived approximately 98.79 million years ago during the mid-Cretaceous period, according to an international research team from China and Denmark who analyzed sixteen female specimens preserved in amber. The team used micro-CT scanning to examine the detailed anatomy of the wasp.
One of the most striking features of S. charybdis was its abdomen, which bore a strong resemblance to a Venus flytrap plant. The abdominal apparatus consisted of three flaps, with the lower flap forming a paddle-shaped structure lined with a dozen hair-like bristles. Researchers suggested that this structure likely served to temporarily immobilize prey during egg-laying.
"The abdominal apparatus of Sirenobethylus is unlike anything previously reported from any extant wasp or indeed any insect known to us," the researchers wrote.
The morphology of S. charybdis indicated that these wasps were parasitoids, meaning their larvae lived as parasites and eventually killed their hosts. Evidence suggested they started developing parasitoid strategies by the mid-Cretaceous. The wasp's unique abdominal structure may have allowed it to target highly mobile prey, such as small winged or jumping insects.
"It's unlike anything I've ever seen before. It's unlike any wasp or any other insect that is known today," said Lars Vilhelmsen at the Natural History Museum of Denmark, according to New Scientist.
The researchers proposed that S. charybdis may have waited in ambush with its trap-like abdomen open, ready to pounce as soon as a potential host activated the capture response. The abdominal flaps would then snap shut to restrain the host while the wasp laid its eggs. The strategy would have been advantageous as the wasp was likely unable to pursue prey over long distances.
"What I find extraordinary is that the abdomen of Sirenobethylus charybdis is a brand new solution to a problem that all parasitoid insects have: how do you get your host to stop moving while you lay your eggs on or in it?" said Manuel Brazidec at the University of Rennes in France.
The team believes that the peculiar features of S. charybdis warrant the establishment of a new insect family, Sirenobethylidae, due to hind wing vein patterns that differ greatly from today's Chrysidoidea superfamily. The analysis revealed that the closest analogues of the wasps in amber were modern-day parasitoid species of the superfamily Chrysidoidea, which include cuckoo wasps that lay their eggs in the nests of their hosts and bethylid wasps that paralyze their prey before laying eggs into the victim.
"Our findings suggest that Chrysidoidea displayed a wider range of parasitoid strategies in the mid-Cretaceous than they do today," the researchers wrote.
The absence of male specimens of S. charybdis makes it challenging for the team to fully understand the species' reproductive behaviors and whether the abdominal apparatus could have been involved in the mating process. "It's difficult to verify this theory without being able to compare these female specimens with the species' males, which are missing from the record," the researchers noted.
As they continue to study these specimens, the researchers emphasize how discoveries like these shed light on the diversity and complexity of ancient insect life. Vilhelmsen reflected on the significance of the find. "It was very exciting, but it was also a challenge, because how can you explain how this animal worked when you have nothing like it today?" he said.
The article was written with the assistance of a news analysis system.