Life hides in small places. Turn over a wet rock and you’ll find a few roly poly bugs doodling paths through the soil. Poke one, and it’ll curl up its armored body into a ball. And the thing is—even though roly polies live a bug-like existence, they’re not bugs at all, they’re land crustaceans, related to shrimp, brine shrimp (Sea-Monkeys®), krill, crabs, crayfish, lobsters, and other marine arthropods with two-branched limbs and segmented bodies.
Stretched out to its full walking length, a roly poly is about the size of an Ibuprofen caplet. When startled, a roly poly will curl itself into a pill-like ball—a Claritin D if it’s a baby, and Tylenol pill if it’s an adult. This curling-up action is called conglobation. Roly polies conglobate as a protective measure, as well as to retain moisture. If they dry out, they die. And if they’re fully immersed in water, they die. If not for their ability to roll up into a cute little ball, which makes them endlessly fascinating to kids, a roly poly would be your run-of-the-mill creepy crawly, like an earwig or Paul Manafort.
Roly polies have grudgingly adapted to land. They live where few others can, noshing on harmful funguses that can add carbon dioxide to the atmosphere, in addition to devouring soils rich with heavy metals. Unlike marine crustaceans, whose gills distribute gases throughout the bloodstream and body, land crustaceans have spongy gills that store oxygenated water inside their bodies as they gulp down mulch. In essence, a roly poly is a Sea-Monkey® that doesn’t have its shit together, and only a creature as small as a roly poly could make that into a feature instead of a flaw.
In the English-speaking world, roly polies go by many names. Maybe you called them pill bugs when you were a kid. Gardeners love coming up with names for them. Some names are not very pleasing: woodlice (ew), carpenter’s flea (bleah), sow bug (yuck), pill worm (ugh, squish it). And then you’ve got some good ones: doodle bugs, cheesy bugs, butchy boys, boat builders, bibble bugs, odimadods, woozy pugs, chisel bobs, potato bugs, tomato bugs, granny greys, Billy buttons, tiddlyboars, monkey peas, peaballs, crunchy bats, chitty bobs, and chuggie pigs.
Roly polies come from the family Armadillidiidae, in the order Isopoda. There are many different families of roly polies and pill bugs that live in more arid regions of the world. The bluish-grayish roly polies are the most common ones that I know, but you might be more familiar with ones that are more brown or tan where you live. It really depends on how much time you spend looking under rocks. When it comes to identifying differences between different families of roly polies, you can really get into the weeds. It’s like trying to figure out why the Klingons developed ridged foreheads after the original sixties Star Trek. Of course there’s a canonical answer—will knowing it unlock a hidden layer of the universe to you? (Here’s a field guide to identifying Klingon foreheads for your nature walks, by the way.) Anyway, the blue-gray roly polies have sharply angled antennae that stick out even during conglobation, and the brownies have antennae that tuck in. For the casual observer, unless you’re experimenting with macro photography, one person’s roly poly is another’s pillbug, and that’s fine.
Here are some quick and dirty facts: When a roly poly gets sick, it turns bright blue or purple, which is striking in the way an oil slick can be beautiful. Roly polies can snozzle up water with their anus. Instead of urinating, roly polies excrete an ammonia gas. Roly polies eat their own poop. Why would they do that? Well, a roly poly needs a certain amount of copper jangling around its weird little body to live. Each time a roly poly makes a grumpy, it voids all of its copper, and it must return the copper to its body—by any means necessary. That just seems like finding a penny on the sidewalk everywhere you go, but it’s always tails.
So. Knowing all of these intimate details—what is it, exactly, that roly polies do? And why do they do it?
No matter how much humans try to fuck it up, the web of life is a fairly self-sustaining system where all living things contribute within their means to fostering life on Earth. Roly polies play their part, it’s part of their basic operating system: Roly polies’ gill-like lungs allow them to thrive in places where not many other creatures choose to live—moist places (sorry if the word moist is like cilantro to you) with lots of dead plants to munch on. In these quiet spaces, a roly poly finds purpose.
Like earthworms and snails, roly polies help in the decomposition of fauna, returning organic matter to the soil, “where it is further digested by fungi, protozoans, and bacteria, hence making nitrates, phosphates, and other vital nutrients available to plants,” explains a natural resources guide. And, unless you have a tsunami of roly polies flooding your garden, these creatures are not pests. They don’t eat live vegetation or chew through leaves, to settle their tummies after gorging on chocolate cake, ice cream cones, pickles, Swiss cheese, salami, lollipops, cherry pie, sausages, cupcakes, and watermelons, like a very hungry caterpillar. In the natural world, decay is part of life, and a roly poly helps return the nutrients captured in dead vegetation to the soil.
Because of their need to live in damp areas on land, roly polies are particularly suited to thrive in places where few other species can go, like where polluted water has settled into the ground, leaving harmful heavy metals in the soil. Roly polies can eat these heavy metal deposits, like copper, zinc, lead, and cadmium—removing the toxic metal ions and restoring the soil to its natural state.
In this small way, roly polies contribute to the fight against climate change. And they do more. A PBS report on roly polies cited a Yale study about how land crustaceans play a role in slowing climate change:
[Roly polies] consume fungus that is responsible for breaking down organic matter in the soil, a process that releases carbon dioxide into the atmosphere. As the atmosphere warms, the fungus activity increases, resulting in more carbon released and even higher atmospheric temperatures. It’s a dangerous vortex. But when [roly polies] and their kin are present, they’re able to mitigate the effects of increased temperature by consuming more of the fungus. They’re small, but [roly polies] may be protecting us by slowing climate change.
Fossil fuel ideologues can remove articles about climate change from the EPA’s website, but climate change is beyond debate. I find some comfort in knowing there are creatures out there built to maintain a balance whenever balance is possible, but roly polies can only do so much on their own. While they may not have very complex operating systems, roly polies are a benign force: strange land crustaceans driven by obscure purposes to survive. Even the smallest of creatures, ones so inconsequential that we often mistake them for bugs, are not beyond our notice.
Image: Dave Huth via Flickr