Thank you for joining us for this brief bit of election counterprogramming that may or may not make you feel better, depending on how you feel about parasitic wasps. Because, sure, we’re all stressed the hell out, but at least a wasp hasn’t injected you with an egg that hatches into a larva that feeds on your nutrients before erupting out of your body.
But let me back up. The caterpillar stage of the aquatic moth Elophila turbata lives in the freshwater ecosystems of Africa and Asia. It’s a waste-not-want-not kind of critter, feeding on vegetation floating at the surface and using the material to build a case as a protective home. It situates its case amidst the vegetation, just below the waterline. There it lives a peaceful life, munching along, growing bigger, making bigger cases every so often, not worrying about elections.
Then a female Microgaster godzilla comes along. That scientific name is not a mistranslation or a weird bit of Latin, but a very intentional honorific that researchers bestowed upon a species of parasitoid (meaning a parasite that kills its host) wasp in a new paper in the Journal of Hymenoptera Research. The Godzilla of pop culture emerges from the sea to make life miserable for humans, and this wasp does the same for moth caterpillars. Also, Godzilla once fought Mothra, and Microgaster godzilla menaces the caterpillars of aquatic moths.
“I'm guilty of naming many species with funny names,” says the study’s lead author, Jose Fernandez-Triana of the Canadian National Collection of Insects. “In the past, I named one Keylimepie. And I have named a wasp genus Toblerone after the Toblerone chocolate bar. I named one after Crocodile Dundee,” an Australian species, of course. “We have some fun, and why not?” he asks.
Crocodile Dundee ain’t got nothing on our Godzilla wasp, though. To watch it in action, the researchers collected aquatic caterpillars from ponds in Japan and reared the wasps that emerged. They then set each wasp loose in an aquarium in the lab with 20 more caterpillars, and recorded the ensuing chaos with a video camera.
The footage, above, puts any Godzilla film to shame for lack of inventiveness. The wasp strolls along the vegetation that Elophila turbata frequents, searching for an aquatic caterpillar in its case. When the parasitoid finds one, it taps the case with its antennae and dives down to pull it out of the protective shell. Fleeing for its life, the caterpillar surfaces into the vegetation above its home, only for the wasp to emerge from the water, Godzilla-style. The wasp grabs hold of the caterpillar and drives its ovipositor into the squishy body, injecting a single egg.
Unfortunately for the caterpillar, that egg soon hatches into a larva, which feeds on its insides. Exactly what it’s eating at the beginning, Fernandez-Triana can’t yet say. It may be fluids, it may be tissues that are not essential for the caterpillar’s survival. “The reason for that is to allow the caterpillar to accumulate enough nutrients,” Fernandez-Triana says. That is, the parasite wants to keep its host alive to ensure a steady stream of fresh food. “These wasps, they start eating fat tissue, but they don't touch the major organs,” he continues. “So the caterpillar is parasitized—I'm sure it's not feeling well at all—but it continues to live.”
Eventually, though, the caterpillar outlives its usefulness to the wasp. The parasite has grown big enough to make its dramatic escape, and to devour the rest of its host alive. “At that point, the wasp larva will come out of the caterpillar—pretty much like in the original Alien movie—to spin a cocoon from which an adult wasp will eventually emerge,” says Fernandez-Triana. “Needless to say, the caterpillar dies after this.”
This species of aquatic moth is not alone in its travails—other wasp species menace other aquatic caterpillars. “This behavior is rare, but has been documented in well over 100 species from 11 different families,” says Robert Zuparko, a curatorial assistant at the California Academy of Sciences who studies wasps, but wasn’t involved in this work. What may be unique here, though, is that the researchers captured the encounter on camera in the lab. The upside is it allowed them to observe the wasps and caterpillars in a controlled environment, free from complicating factors like weather and other animal species butting in. The downside is that it’s not a one-for-one replication of natural conditions, which means the interaction between parasite and host might be subtly different in the wild.
Now, I know you’re thinking it: Is this wasp larva also mind-controlling the caterpillar? Good question. It certainly wouldn’t be the first wasp to do so: A whole genus of different species called Glyptapanteles inject up to 80 eggs into a single caterpillar. The eggs hatch into larvae and feed on their host’s insides, then all burst en masse from its body. But they’ve taken care to not fully consume the caterpillar, and in fact have somehow convinced it—perhaps by releasing some kind of chemical while inside—to protect the larvae as they spin their cocoons. The poor bastard will violently lash out at any predator that comes near.
But it appears the Godzilla wasp larva doesn’t modify the behavior of its moth caterpillar host, Fernandez-Triana says. This may have to do with predation. Presumably, the Glyptapanteles wasps evolved the ability to turn their hosts into bodyguards because they were under intense pressure from predators on the hunt for the vulnerable young. It may be that the Godzilla wasp larva just doesn’t face the same kind of threat, and can devour its host and be done with it.
So … at least our aquatic caterpillar doesn’t suffer the indignity of its parasite putting it to work. Or have to live through another election.