In a paper published in the journal BMC Biology, paleontologists described an extinct species of koinobiont parasitoid wasp found in mid-Cretaceous amber from the Kachin region of Myanmar. Named Sirenobethylus charybdis, this species may have used its Venus flytrap-like abdomen to capture and immobilize its prey.
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Sirenobethylus charybdis. Scale bars – 0.5 mm in (A), 0.3 mm in (B), 0.2 mm in (C). Image credit: Wu et al., doi: 10.1186/s12915-025-02190-2.
“Insects are the most diverse group of animals on the planet, with more than one million described species and probably several times more undescribed,” said Capital Normal University paleontologist Taiping Gao and colleagues.
“Recent estimates suggest approximately 5.5 million species in total.”
“Their highly adaptable exoskeleton has allowed them to radiate and colonize a wide range of habitats and develop highly efficient and innovative solutions to a range of challenges posed by their surroundings.”
“Among other mechanisms, carnivorous insects have evolved a range of prey capture mechanisms.”
“However, insect predation strategies in the fossil record remain poorly understood.”
In the new study, the authors examined sixteen adult females of Sirenobethylus charybdis found in Kachin amber.
The new species lived during the mid-Cretaceous period, approximately 99 million years ago.
The morphology of Sirenobethylus charybdis indicates the insect was parasitoid — insects whose larvae live as parasites and eventually kill their hosts.
“Modern-day parasitoids of the superfamily Chrysidoidea include cuckoo wasps and bethylid wasps,” the researchers said.
“However, the Sirenobethylus charybdis specimens possess a unique pattern of veins in the hind wing that suggests the species belongs within its own family, the Sirenobethylidae.”
The scientists also found that the species was likely to have been a koinobiont — a parasitoid which allows its host to continue growing while feeding on it.
“The wasp specimens have an abdominal apparatus comprised of three flaps, the lower of which forms a paddle-shaped structure with a dozen hair-like bristles, visually reminiscent of a Venus flytrap plant,” they explained.
“The abdominal apparatus of Sirenobethylus charybdis is unlike that of any known insect, and may have served as a mechanism to temporarily restrain the host during egg-laying.”
“As the wasp was likely unable to pursue prey over long distances, it would have waited with the apparatus open for a potential host to activate its capture response.”
“The elaborate grasping apparatus allowed Sirenobethylus charybdis to target highly mobile prey such as small, winged or jumping insects.”
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Q. Wu et al. 2025. A cretaceous fly trap? remarkable abdominal modification in a fossil wasp. BMC Biol 23, 81; doi: 10.1186/s12915-025-02190-2
