Parasitic 'horror' wasp that bursts from a fly's abdomen like an 'Alien' xenomorph discovered in Mississippi backyard

Researchers in Mississippi have discovered a previously unknown species of parasitoid wasp that matures inside the bodies of living, adult fruit flies before bursting out of them like a xenomorph in the "Alien" movies.

The sneaky predator, which researchers have named Syntretus perlmani, is the first wasp found to infect adult fruit flies — similar wasp species are known to target flies during their younger, more vulnerable larva and pupa life stages. The wasps are parasitoids rather than parasites because they always kill their hosts, while parasites usually don't.

A team of scientists came across the wasp by chance while collecting a common fruit fly called Drosophila affinis in their backyards in Mississippi. They published their findings Wednesday (Sep. 11) in the journal Nature.

Study lead author Logan Moore, a biologist who worked on the research as part of his doctorate at Mississippi State University, told Live Science that female S. perlmani use their needle-like ovipositor organ — the stinger in stinging wasps — to stab and deposit an egg within a fruit fly's abdomen. The egg then hatches into a tiny wasp larva, which grows inside the fly for about 18 days before leaving its host for dead.

"It will effectively emerge out of the side of the fly," Moore said. "And just to add an additional layer of horror, the fly will normally remain alive for several hours after that."

Related: These bacteria trigger a sex change in wasps — scientists finally know how

The researchers were screening fruit flies for parasitic worms called nematodes in March 2023 when they first came across a spiky-tailed wasp larva inside the abdomen of one of the flies.