"Holy Moly Roly Poly!" This enthusiastic shout came from an adorable, towheaded 4-year old, standing on the far side of a log I’d just rolled toward me. Together, we paused to watch a dozen or more oval gray invertebrates with lots of legs scurry in confusion around their suddenly well-lit home. Then I let the log roll gently back to its original position. We continued down the trail…or rather I continued down the trail, and the boy joined his friends in splashing along the small creek.
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| Two Armadillidium nasatum, one likely Trachelipus rathkii found under the log. Photo by Emily Stone. |
This child’s exclamation was my favorite moment of a fun-filled morning with about 20 kids and their adults at the Kishwauketoe Nature Conservancy in William’s Bay on Geneva Lake in southern Wisconsin. The popular “Kish Kids” program began at the picnic shelter with me introducing the magic of a “treasure finder.” This device is imbued with special powers that guide its path. So when you toss a treasure finder (gently, not too high, and not at your friends,) it will always land on something special.
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These kids hardly needed help! The gadget found vibrant green grass, a web of fungal mycelium, and clover making sugar. But just the act of slowing the kids (and adults) down meant that they found spider webs covered in dew, colorful grasshoppers, a pooping snail, monarch eggs on milkweed, and so much more. By the time the 4-year-old and I had rolled over the log, the treasure finder was completely unnecessary for discovery.
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| This yellow garden spider was an early highlight of the walk! Photo by Emily Stone. |
The discovery continued when I got home. Just based on that boy’s enthusiasm, I knew I needed to write about roly polies. As a start, I uploaded a few of my photos to iNaturalist. To my surprise, all three photos were of different species!
Initially, iNaturalist helped me identify one species as the spurred ridgeback isopod, Haplophthalmus danicus. While they are native to Europe and Asia, entomologists believe they were brought to this continent during the original European settlement—stowed away in the pilgrims’ potted plants and ship ballast, perhaps? When I went back to my observation a few days later, though, two different people with specialties in isopods had made much more educated IDs. This is one of the benefits of posting observations to iNaturalist!
The experts’ IDs, the nosy pill woodlouse (Armadillidium nasatum) and Rathke's woodlouse (Trachelipus rathkii), are two more European species who were brought here, probably by accident. When the nosy pills roll up, they don’t quite form a complete ball, so maybe they don’t technically fit the kid’s ID of roly poly? I called those sow bugs as a child.
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This Rathke's woodlouse
made their home under a log near a creek in southern Wisconsin. Photo by Emily
Stone. |
The common pill bug, aka common pill woodlouse, roly-poly, potato bug, slater, doodlebug, carpenter, wood shrimp, chiggypig, penny sow, cheesybug or Armadillidium vulgare, was the most interesting find of that log. They are introduced from Europe just like the others, but according to the World Catalog of Terrestrial Isopods by German entomologist Helmut Schmalfuss they are “the most extensively investigated terrestrial isopod species.” The benefit of having that title is that we know all sorts of cool facts about their lives!
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The common pill
bug, aka common pill woodlouse, roly-poly, doodlebug, chiggypig, penny sow, cheesybug
or Armadillidium vulgare is a little critter who loves to live in the
damp darkness under rotting logs. Photo by Emily Stone. |
Many of pill bug’s adaptations are centered around not drying out. Isopod’s ancestors evolved in the sea, and the lungs on their bellies still need a thin film of water to work. So they live in damp soil underneath rocks or rotting logs that provide shade and prevent evaporation. They don’t need complicated eyes; they just have a simple photoreceptor to detect light and dark. They huddle with their relatives and seek out tight corners to reduce water loss through evaporation. They often forage at night, on the gourmet fare of decomposing plant litter, with a few seeds, live plants, dead animals, fungi, and some scat thrown in.
By nibbling on fungi, pill bugs reduce the amount of carbon dioxide that the fungi release through decomposition. This may make a small contribution toward reducing climate change, especially when you consider that some locations support up to 900 pill bugs per square foot!
In order to keep their eggs from drying out, pill bugs are an invertebrate version of marsupials. Three times a summer the female places a dozen or so eggs into the nutrient-filled water of her brood pouch. Once they hatch, the young will remain in the brood pouch for a few days before emerging as juvenile adults. Since exoskeletons can’t grow, the juveniles need to molt twice to achieve all seven body segments and seven pairs of legs.
The seven segments in their thorax’s tough exoskeleton allow piddlebugs to roll up into a tight ball for protection against predators, which include spiders, centipedes, beetles, and salamanders. If the danger overwhelms them, common pill bugs may play dead just like their buddy in marsupiality the opossum! The towhead and I must not have seemed dangerous, because none of the isopods even rolled up when we flipped the log.
Climate-mitigating, marsupial invaders who play dead? Holy Moly Roly Poly indeed!
Emily’s award-winning third book, Natural Connections3: A Web Endlessly Woven, is available to purchase at www.cablemuseum.org/books and at your local independent bookstore, too.
For more than 50 years, the Cable Natural History Museum has served to connect you to the Northwoods. Our Summer Calendar is open for registration! The Museum’s new exhibit, The Wetland Way is now open! Discover how life thrives at the intersection of soil and water, and why we must care for these special places as they care for us. Follow us on Facebook, Instagram, YouTube, and cablemuseum.org to see what we are up to.
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