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Fossilized Wasps Showcase Unique Predatory Strategies of the Past
Recent examinations of ancient insects trapped in amber have illuminated an intriguing evolutionary path which concluded after the mid-Cretaceous period. An international team of researchers has analyzed several specimens dating back approximately 99 million years, unveiling a previously unknown wasp species characterized by abdominal appendages reminiscent of a Venus flytrap. These adaptations allowed the wasps to capture other insects efficiently before laying their eggs within them. The findings were published on March 26 in the journal BMC Biology.
Approximately 10 percent of known insect species are classified as parasitoids, which require a host for larval development, often resulting in the host’s demise. However, none of these contemporary insects bear resemblance to the extinct species Sirenobethylus charybdis. Recent studies, particularly involving 16 amber-preserved female specimens discovered in Myanmar’s Kachin region, suggest that S. charybdis may represent an entirely new lineage of insects. This identification arose from the unique vein structure of their hind wings, which substantially differ from the current Chrysidoidea superfamily, which includes common wasps like cuckoos and bethylids.
Abdominal terminal of the specimen displaying the grasping apparatus. Credit: Qiong Wu
Aside from the distinctive hind wings, S. charybdis exhibits an exceptional three-flapped abdominal structure that resembles the traps of a Venus flytrap. The lower flap, characterized by fine bristles, stands out among its features.
“The abdominal apparatus of Sirenobethylus is unlike anything previously reported from any extant wasp or indeed any insect known to us,” the research team noted in their paper.
The researchers proposed two theories regarding the function of these intriguing appendages. The primary hypothesis suggests that the females might have utilized these jaw-like extensions during mating; however, with no male specimens available for study, this concept remains speculative. The team acknowledged the rarity of females gripping males during mating within the insect kingdom.
“Indeed, it would be unique for insect females to restrain the males during mating, rather than the other way around,” they explained.
Reconstruction of Sirenobethylus charbybdis. Credit: Xiaoran Zuo
In a more unsettling conjecture, it is postulated that S. charybdis utilized its specialized appendages to ensnare potential hosts rather than consuming them directly. Instead, these wasps likely subdued their prey to facilitate egg-laying, maximizing opportunities to target more active insects. When the appendages detected movement—triggering the hair-like bristles—it could close around the unsuspecting victim, completing the predatory cycle. Additionally, given the positioning of its stinger on the dorsal side of the middle flap, it is conceivable that S. charybdis inflicted a sting on the host larvae as well.
The timeline and reasons behind the extinction of this terrifying wasp remain uncertain. Nevertheless, its discovery sheds light on the early evolutionary strategies employed by some Chrysidoidea species to adopt parasitoid behaviors by the mid-Cretaceous. Sirenobethylus charybdis, named after the menacing sea creature from Greek mythology in The Odyssey, exemplifies a predatory lifestyle that remained one step ahead of its prey.
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