It may have made for the perfect lesson, but it was a discovery that no invasive species expert wants to make.

During a workshop on invasive species last October, University of Wisconsin-Madison Arboretum leaders took students into the field to show them, theoretically, how to survey for invasive species.

But as a Wisconsin Department of Natural Resources invasive species expert was explaining how the ground would change if a specific species of earthworms was present, the class got a much more realistic lesson than they were expecting.

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“We went out to the woodlands and Bernie (Williams) was telling them about this Asian worm that we’re on the lookout for, but that’s not here yet. And then there it is, jumping and snaking around,” said Brad Herrick, an ecologist at the arboretum.

It was the first confirmed sighting of Amynthas agrestis in Wisconsin, although it’s been found in the Southeast and East since it was reported in the southern Appalachians in 1993.

The worms, also known as "jumping" or "crazy" worms, can be inadvertently transported to the United States from their native Japan and the Korean Peninsula along with imported landscape plants.

The fear of the jumping worm in a new habitat is that the forest floor will become barren, reducing the regeneration of trees and making it more hospitable for other invasive species.

“This particular invasive worm is very large and aggressive, and it reaches maturity very quickly,” explained Monica Turner, a University of Wisconsin-Madison zoology professor. “It eats its way through the soil faster than other earthworms.”

The jumpy worm, UW Arboretum

It also appears to be hardy, surviving the past winter, Wisconsin’s coldest in 35 years. Although the effect on vegetation is obvious, there has been little research on long-term effects of the worm. So Turner and her students have begun a study of the critters and hope to have some initial data by spring 2015.

“Because we know the starting conditions, we will be able to compare changes in the soils with and without the worms to see what they can do within one season, and how that varies with soils from different kinds of ecosystem,” Turner said.

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A second, observational study will measure soil characteristics at locations within the arboretum that have been invaded by the worms versus locations that have not.

Ironically, the worm species that Amynthas agrestis could threaten is not native, either: The worms commonly found in Wisconsin and the Midwest arrived from Europe with the first settlers.

While the worms are not welcome, there are too many unknowns to say exactly where they fall on the spectrum of invasive species nastiness, Herrick said. Unsuspecting gardeners may actually appreciate them for the high nutrient soil they help create.

“But they do more harm than good,” Herrick said.

The arboretum is limiting access to infected areas, and staff there are washing boots, tires, and tools of anything that gets near the worms, to control their spread.

Meanwhile, people who see the worms in their gardens should contact the local department of natural resources, Herrick said. They can be identified both by their active, jumpy behavior and their white rings.