The BioGeek Memoirs: Pill Bug

Okay, you know this little guy well. I think that I first called him a roly poly when I was a child because… if you mess with them or pick them up they roll up into a little ball. Those little rolled up bugs look a little like pills, hence the alternative name: pill bugs. I suspect that we were kind of mean to roly polies when we were kids. Poor guys.

Roly poly from my garden.

I have quite a few of these critters hanging out in my garden. They appear in the loose dirt as I pull out weeds, move stones, and dig around in my gardens. They build extensive tunnels under my bricks in the side garden and are feasting away on the leaf and mulch debris and landscape timber around my gardens. They are, essentially, decomposers and really excel at that niche in the garden ecosystem. Can they also eat leaves, roots, and other things that I want to grow in the garden? Well… yeah. They can be a problem, but I think that since I mulch pretty aggressively due to our dry climate that hasn’t been an issue for me.

Did you think that they were insects? I mean, we call them pill BUGS. Nope. They are actually a type of crustacean. As in, they are land dwelling cousins of lobsters and crayfish. They rely on gills to obtain oxygen, and they have other characteristics common to crustaceans like the hard exoskeleton, jointed appendages and two sets of antennae on their heads. (One set is not visible to the curious gardener. Bummer. I have looked.)

These isopods (that’s the name of the crustacean group that they belong to) are also called potato bugs. That is kind of my favorite because you can catch them by cutting a potato in half, scooping out most of the inside, and then putting the potato back into the garden where it will attract pill bugs for you. Easy peasy, right? Here’s a little video that shows how to catch them with a potato.

That explains why I used to take some potatoes to school with me, make a couple of potato traps in my AP Biology class, and then assigned the class the homework of catching 10 potato bugs each over the next week.

Say what?

I used the pill bugs in class to do a lab with them that helped them identify animal behaviors and to also learn some things about experimental design with live animals. Poor little guys. They became the star performers in an open-ended inquiry lab where students had to generate an hypothesis, create the test chamber, collect data, and then draw conclusions from their results.

Choice chamber made from petri dishes. There is a little door between the dishes that lets the potato dudes move between the chambers.

I know, I know… those aren’t pill bugs! I dug around in my bead collection and found these to stand in for the real things. (Um… it is winter and snowing outside…) Still, you can get the idea of how this worked. The students would set up the chambers to offer the pill bugs a choice between the two sides; the pill bugs would run around like crazy and the students would collect data that would (hopefully) reveal a clear preference in their environment. Try to imagine student teams trying to set up the chambers and then getting in 10 pill bugs, putting the lids onto the dishes without harming one of their experimental animals, and all the chaos that ensued. Shrieking. Escaped pill bugs. Ice cubes melting on lab notebooks…

The trick was to offer the isopods a clear choice: wet/dry, warm/cold, sweet/salty, or maybe covered/open conditions.

The second trick was to make sure that the isopods were being offered only one choice.

The final (and most important trick) was to figure out how to collect data and then process it. Teams struggled to come up with a data table. Once you have the data, how do you make meaning from it? Most teams decided to count the number of critters in each dish every 30 seconds and then graphed the results to show the preferences.

At the end of the lab cycle the pill bugs were all released in the landscaping right outside my classroom where they went back to their best little pill bug lives in the bark mulch and plantings along the front of the building. My principal never caught on to what my class was up to, but he did once ask me why kids from my class were frantically digging through the mulch out front. “Oh. Those kids forgot to do their homework on time,” I said as I beat a path out his office door. Poor man. He had been an English teacher before he became a principal.

So, what do pill bugs like? They like to be under cover. They also prefer damp to dry, cool is much better than warm (they will all stand on an ice cube to try to get away from the warmer dish), they avoid salt, and they prefer rotting potato to fresh potato.

I loved this lab. I always used it towards the start of the year as it was extremely helpful in establishing good practices in hypotheses, experimental designs, data presentation, dependent and independent variables, and, of course, lots of details about pill bugs and animal behavior. It was helpful in establishing norms and lab expectations in my classroom in a lower risk environment (unless you were one of the pill bugs) as other labs involved more chemicals, sharp instruments, and stressful time constraints.

All that comes back to me every time I weed the garden and the roly polies emerge, potential experimental animals, each one of them.

Pill bugs and the advancement of scientific knowledge.

I bet that you will never look at pill bugs the same again.

Author: Midnight Knitter

I weave, knit and read in Aurora, Colorado where my garden lives. I have 2 sons, a knitting daughter-in-law, a grandson and two exceptionally spoiled kittens. In 2014 I was diagnosed with a serious rare autoimmune disease called systemic sclerosis along with Sjogren's Disease and fibromyalgia.

20 thoughts on “The BioGeek Memoirs: Pill Bug”

  1. This was so interesting! I actually gasped when I read that they are crustaceans. That is a very good lab idea, I wish my teachers would have done something like that. You must have been a great teacher. The biogeek memoirs are the best part of the blogging week.

    1. I really, really loved my job! I think that it’s best to get in as much hands-on stuff as possible to support the concepts that they are getting in the book and class discussions. I’m a true BioGeek for sure!

  2. Very cool! I didn’t know any of that except they rolled up into a ball. Thanks for a great science lesson!

    1. I’ve never seen one indoors, but it is really dry here and they would never survive. Woodlice! No wonder you never played with them or you would know that they roll up. I’m pretty sure that we tried to play marbles with the poor things when I was a child.

  3. Fascinating– your students must have really enjoyed it and loved having you for a teacher.. i hadn’t realized that pill bugs aka roly polys (sp?) were also called potato bugs. And i certainly will put them on my ‘A’ list of bugs! (i also like most spiders ).

    1. I think that I was pretty good, but never as good as I wanted to be. It was always a moving target. I like some spiders too! I have an idea for a post about orb weaver spiders but I haven’t gotten a good picture yet. I may have to resort to using a photo service for some of these.

    1. Isn’t that a riot? I was a little shocked when I found out. They have gills! No wonder they prefer damp conditions and can become a problem in wet climates. Mine are very well behaved in my garden and probably didn’t deserve to become experimental animals, but that’s the life of a pill bug. One day you’re snacking on a piece of rotting potato, and the next you are off to high school!

  4. Never too old or too late to learn! Enjoyed this very much. I do indeed remember those roly polies and how we always had fun getting them to roll themselves up. We never killed any that I recall but they were fascinating to us like hedgehogs and porcupines were as well. Blew my mind when you said that they are a type of crusatacean though. And then that they are a class of land crustacean…..🤯 that is a thing?! What a fascinating little “bug” and class experiment!

    1. I am so relieved by positive comments like yours. I wasn’t sure if my geeky love of the natural world would be well received by anyone else. Thank you for the nice comment! I remember being fascinated by how they rolled up too. So cool! I have no experience with hedgehogs in the wild (a student once brought one in to show me… this is what happens when you are a biology teacher) but every encounter with a porcupine was as an adult. Yep, visualize me clutching my friends as we all backpedaled frantically away from porcupine. We have armadillos here… so cool! The whole rolling up thing is just fascinating.
      Inquiry labs are hard to do. I had another one that was pretty successful that featured yeast, but who wants to read about that?

  5. That was really interesting! I had no idea they were crustaceans! That sounds like such a great series of experiments you had your class doing – I would have loved something like that too 🙂

    1. I think that all children are just charmed by things like roly polies (AKA pill bugs) because they are so… cute. I have heard them called sow bugs, but that is just crazy bug talk right?!

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