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Catching prey can be a real chore when you’re a parasitic insect desperate to catch a meal for your babies. Sometimes it’d be easier to let your bum do all the work for you.

Sixteen female adult wasps found preserved in amber for 99 million years may have done just that. Named Sirenobethylus charybdis by the researchers studying the fossils, the new-to-science species features an odd assortment of flaps on its abdomen. These flaps may have allowed the wasps to grip grubs and insert eggs into their bodies.

“Nothing similar is known from any other insect,” wrote the team of scientists, who were led by researchers from Capital Normal University in Beijing.

While they can’t be certain the strange anatomy was used this way, there are clues which make these body parts look perfect for gripping, such as rows of bristles lining the flaps.

The wasp seems to be a type of parasitic insect that uses a needle-like appendage to inject its eggs into a living host. Once the young hatch, they feed and grow inside their host. As gross as it might sound, many insects today use this method to raise their young on slow-moving prey like caterpillars, maggots and grubs.

But today’s parasitic insects seem to do it by actively hunting their prey and snatching it with powerful legs, something this wasp doesn’t seem to be able to do. Instead, it may have sat quietly, waiting for prey to crawl by. The three bristled flaps may have then latched onto the hapless grub, giving the Sirenobethylus charybdis time to inject its eggs.

It’s also possible the bristly flaps may have been used by wasps to hold onto mates, though the researchers think this is unlikely. Finding fossilised males of the same species without the flaps could one day help confirm their use as mum’s bum trap.