Happy Halloween!

By Daniel Barringer, Preserve Manager.

Photo: Daniel Barringer

It’s a time of year when we enjoy frightful things, so how about this hammerhead flatworm, a three-lined planarian (Bipalium pennsylvanicum) below?

Photo: Daniel Barringer

Actually—I don’t find these frightening, merely interesting; these hammerhead flatworms don’t cause us harm. They’re not native, and they could be having some ecosystem impact if their population size grew large enough. They eat earthworms—themselves not native here—and it’s not really known what their populations are. And even if invasive that would not be a reason to demonize the species itself; they didn’t transport themselves halfway around the world on their own, and if successful here, that doesn’t make them evil.

Wanting to know how common hammerhead flatworms are in Pennsylvania is the reason that iMapInvasives included the species in this year’s Invasives Scavenger Hunt. If found during the month of August we participants could record it on the iMaInvasives website. I didn’t find any during that month, not surprising since it was so dry, and you usually see these when it’s wet. But I had seen them previously and just found this photo I took along our front walk in 2018.

If you’d like to learn more about hammerhead flatworms look at this Penn State Extension web page.