Terrifying Parasitic Wasps Knife Their Way Out of Bug Corpses With Spikes on Their Backs

Those aren't just strange bumps on this wasp's back—they're blades. Carolyn Trietsch

Wasps have a bad reputation for their sharp stingers, but a new species of wasp appears to take inflicting pain to a whole new level. Scientists believe the parasitic wasp grows up in another animal's body and then, once it reaches adulthood, saws its way through the host's body to freedom, according to a recent paper published in Biodiversity Data Journal.

The authors of the new paper studied four individual wasps—two males and two females—that had been collected from Costa Rica in 1985 and placed in the U.K.'s Natural History Museum in London and the Frost Entomological Museum in Pennsylvania. These wasps are absolutely tiny—2.7 millimeters, about twice the size of a grain of sand.

The insects' size is part of why they've been sitting around for 30 years. "Some of them are very common," lead author Carolyn Trietsch, a doctoral student at Penn State University, told Newsweek. "The problem is because they're so small no one has really studied them in depth before."

She added that she knew as soon as she saw the specimens, they were something new. But making a formal species identification in the insect world also means carefully studying the samples and comparing them with other, known species. In particular, they dissected the male wasps' genitalia to examine under the microscope, since those vary dramatically, even between species that otherwise look pretty similar. That work confirmed that these wasps are definitely something special, and the team decided to name them Dendrocerus scutellaris.

Because the team was using only museum specimens to study the new wasps, they don't know for sure how these critters live their lives—but thanks to close examination of the wasps' bodies, they can make some educated guesses.

Those aren't just bumps on this wasp's back—they're blades. Carolyn Trietsch

Often, parasitic wasps have a mean jawline. That's to help them break out of the comfy homes they grow up in when they reach adulthood, usually killing their host in the process. The new wasp doesn't have the equipment to eat their way to freedom—but it does have a trio of spines along its back, like a stegosaurus, not found in any of its relatives. That makes the researchers suspect the wasp uses them like a saw to cut its way out of its host.

All of that sounds awfully gruesome, but there's nothing to fear from these wasps. Parasites are a hugely important part of ecosystems, keeping other species' populations in check. In fact, recently scientists have raised concerns that we aren't doing enough to protect them, but have become too distracted by their more traditionally charismatic hosts.

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In fact, these species could be a priceless addition to our knowledge of the natural world, Matthew Buffington, an entomologist at the Smithsonian Institute and the U.S. Department of Agriculture, told Newsweek. After all, these tiny wasps are killing off whatever they grow up inside—and that could well be a species of bug that chomps away at our crops.

"We can regulate pest populations without having to use pesticides if we can use these wasps instead," Buffington said. He was involved in identifying a similarly tiny wasp that eats its way out of the eggs of the brown marmorated stink bug, a pest particularly common in New York, Pennsylvania and Ohio. Now that the wasp has been formally identified, it can be used to control those stink bugs.

And there are likely other "nano-wasps," as Buffington calls them, just as intriguing as these waiting to be spotted in museum collections. "Insect biodiversity is incredible and there just aren't enough taxonomists to look at it right now," Trietsch said. "We have all these new species just waiting to be described."