Key Takeaways on Parasitoid Wasps
Parasitoid wasps lay their eggs in or on their hosts. The wasps' larvae then consume the host, sometimes from the inside out.
Parasitoid wasps can be found on every single continent except Antarctica.
Some species have formed a defense against these parasitoid wasps. They may seem terrifying, but there is a way to prevent them from consuming their prey.
The Xenomorphs from the Alien movie franchise were inspired by parasitoid wasps. That doesn’t surprise Scott Egan, an evolutionary biologist at Rice University. He tells his students that if you can think of a weird interaction between creatures, then he’s pretty confident insects have evolved it at least once.
For those of us who don’t write horror, parasitoid wasps are not particularly inspiring, but they are undoubtedly fascinating. Learn more about these insects and their near-horror-inducing reproduction methods.
Parasitoids Lay Their Eggs In or On Other Organisms
Parasitoids are organisms that lay their eggs in or on the bodies of other organisms.
The eggs then develop, eventually killing the host. It’s the “eventually” part that makes this lifestyle so chilling.
Yes, it’s gruesome. And weird. But it’s weird only to us. In the insect world, it’s a fairly common adaptation. The parasitoid lifestyle has evolved many, many times within insects, explains Egan.
Parasite Wasps Are Found Almost Everywhere
There are parasitoid beetles, parasitoid moths, parasitoid bees, and lots and lots of parasitoid flies. But wasps are probably the most numerous, Egan says. In just one group within the parasitoid wasps, there may be more than a million species, and parasitoid wasps live on every continent except Antarctica.
Most are terrestrial, though a few live in freshwater, and one parasitoid wasp attacks a spider that lives in a tidal zone. As you might imagine, with so many parasitoid species, there are many methods to this grisly madness. Some live on, not in, the host. Others offer a bit of mercy, killing their hosts more quickly.
Read More: The Problem with Parasites
Common Prasitoid Wasp Hosts
Though there are many variations of parasitoids, the most famous example is probably Cotesia glomerata, a parasitoid wasp that preys on caterpillars. C. glomerata injects its eggs into a caterpillar. When the eggs hatch, the larvae eat the caterpillar from the inside out. And the caterpillar is still alive while it’s being eaten.
Some parasitoid wasps take a different page from the science-fiction script. Ampulex compressa, or the jewel wasp, injects not eggs but a cocktail of neurotoxins into the brains of roaches, turning the roaches into very docile zombies. The wasp leads the zombie roaches back to its nest, where it lays its eggs on them. When the eggs hatch, the young devour the still-living roaches.
Egan has discovered a species of parasitoid wasp he dubbed the crypt-keeper wasp. This wasp attacks another type of wasp — the gall wasp. Gall wasps lay their eggs in oak trees and manipulate the oak tree into creating a cozy home, called a crypt, for the wasp’s young. If you’ve noticed what look like little tumors on oak trees, you’ve been looking at gall wasp crypts.
The tiny crypt-keeper wasp lays its eggs inside the crypt, and allows its young to grow alongside the gall wasp’s babies. When the gall wasp reaches adulthood and begins burrowing its way out, the crypt-keeper wasp, which is still in the crypt, stops the gall wasp from burrowing any further, plugging the gall wasp’s head in the hole. The crypt-keeper then consumes the gall wasp, starting from the abdomen and eating all the way through the body and emerging through its face. “So, yeah, that's why I call that the crypt-keeper wasp,” says Egan.
Parasite Wasps Aren't All Dangerous
Hosts aren’t totally helpless in the face of these wasps. They may not have Ripley, but they do have defenses. Matthew Ballinger of Mississippi State University studies the interactions between hosts and wasps and their microbial symbiosis. Wasps have powerful venoms, he says.
“If your whole strategy is to lay living offspring into another living host, you’d better have a way to make that hostile environment more friendly for your baby.”
But that doesn’t always work for the wasps. In some cases, bacteria that live in the host kill the wasp, and the host survives. On the other hand, egg-laying wasps have some very specialized ways to target that response.
“These things go back and forth, and the venom figures out a way to shut down the host response, and the host comes up with a new way to block those venoms,” Ballinger says.
Some insects protect themselves by attacking the eggs, explains Egan. Their immune cells encapsulate the eggs, keeping them from hatching. Other insects take a preventive approach by eating foods that are toxic to the wasps, basically medicating themselves.
The lifestyles of insects can be monstrous, at least from our perspective. But for insects, it’s just another day at the crypt. Who needs movies when you have sci-fi horror right outside your door?
Read More: How a Zombie-Ant Fungus Can Infect a Host
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Butterfly Conservation. Beware of zombies
Natural History Museum. Body snatchers: eaten alive by parasitic wasps
Australian Museum. Predators, parasites and parasitoids
Current Biology. Parasitoid wasps
Frontiers in Immunology. How to eliminate pathogen without killing oneself? Immunometabolism of encapsulation and melanization in Drosophila
Avery Hurt is a freelance science journalist. In addition to writing for Discover, she writes regularly for a variety of outlets, both print and online, including National Geographic, Science News Explores, Medscape, and WebMD. She’s the author of Bullet With Your Name on It: What You Will Probably Die From and What You Can Do About It, Clerisy Press 2007, as well as several books for young readers. Avery got her start in journalism while attending university, writing for the school newspaper and editing the student non-fiction magazine. Though she writes about all areas of science, she is particularly interested in neuroscience, the science of consciousness, and AI–interests she developed while earning a degree in philosophy.
