An invasive species of caterpillar has been seen occasionally in the United States over the last couple of decades, but scientists have only just discovered the scale of devastation they can wreak on a native moth.
What's happening?
As Newsweek detailed, the spongy moth caterpillar is native to Europe but has been feasting on U.S. trees for around 20 years. They are known to strip trees of their leaves, and large populations have the capability to cause untold damage to forest areas.
"They're the most destructive defoliators in North America," entomology professor emeritus at the University of Wisconsin–Madison Rick Lindroth told Newsweek. "And they can strip hundreds of square miles of forest bare."
After witnessing a huge mass of spongy moth eggs in the forest while attempting to conduct research, the University of Wisconsin-Madison research team decided to change tack, choosing instead to investigate how these caterpillars can affect a native species of moth.
When defoliated aspen trees produced new leaves, those leaves were found to have eight times more defensive compounds in them than the previous batch.
These compounds are toxic to insects, and researchers fed the leaves to native caterpillars of the polyphemus moth to see how they'd react. Only 18% of the caterpillars survived, with the rate of survival being considerably higher for those feeding on non-infected leaves.
Why is this concerning?
The polyphemus moth is the second-largest moth species in North America, according to Newsweek.
Lindroth noted that despite the two insects never meeting each other, the spongy moth caterpillars can still be deadly for polyphemus moths.
"We're seeing an invasive species harm a native species—a cherished, charismatic, beautiful moth—by changing the quality of its food plant," Lindroth said.
But it's not only the polyphemus moth that's at risk. The spongy moth caterpillar has a large number of suitable host plants compared to other moth species, meaning its destructive path is not limited to just one or two types of plant.
The spongy moth caterpillar's feeding habits can also affect other insects and mammals, while it can also have a notable impact on a forest's ability to absorb planet-warming pollution from the air because of stunted growth among infected trees.
"In every breath that you take, there are molecules of oxygen that were produced by aspen trees," Lindroth added. "It's a very important forest species, and to see the effect of an invasive insect ripple out into the forest community through changing the toxicity of the food landscape is astounding."
What can be done about the spongy moth caterpillars?
You can report the presence of invasive insect species to your state regulator, and the U.S. Department of Agriculture can help you find the appropriate contact details.
Meanwhile, the department calls for vigilance because the spongy moth caterpillar is a known "hitchhiker," with people unknowingly spreading the egg masses when they move items located outdoors. Keep an eye out for any egg masses if you live in a quarantine area, and dispose of them in hot, soapy water, or in a sealed plastic bag that should then be left in the sun.
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