Rock Flipping: Two Worms and a Pill-bug

Today is International Rock Flipping Day, a day to get outside and discover what critters lurk below rocks at the edges of our backyards, vacant lots, alleyways, and other wild and not-so-wild places.


I was a bit worried about this day.

For one, nights and mornings have been rather cool here lately; we even had our first (albeit very light) frost a few mornings ago.  Would some of the critters already be gone for the year?  And second, I live in a dry climate.  Most of the nearby rocks are baked by the sun and surrounded by parched dry grasses – not the most appealing setting for animals that like cool, damp, shady locations.  And we don’t have a lot of rocks to begin with.

Would I find anything under my rocks?

I started in my backyard.  I flipped two rocks.  Nothing.  I walked all over our yard, around the trails, down the hill.  No more rocks.

I thought that a damper, cooler location might be more promising, so we headed for a nearby creek.  The creek is next to a rest area that is right beside a busy highway.  As we scrambled over slippery wet rocks and dodged low-hanging branches, all I could hear was the sound of constant traffic thundering over the bridge.  The creek was beautiful, but it wasn’t a very appealing place to spend time.  And yet, I thought, what a perfect example of a place that is “at the edge of the ordinary.”  Only a few metres away from the highway, yet tangled with wild trees and bushes.

We flipped a rock.  Nothing.  And another.  Still nothing.

The creekside was becoming more and more impassable.  We decided to try one more rock (pictured in the above photo).  It was on the bank next to the creek, high enough that the space beneath it would not fill immediately with water, but low enough to remain damp and cool.

We flipped it.  And there was life!


Two worms and a pill-bug!  Or maybe a sow-bug.  Or a different related species.  I don’t know how to identify different species (and I only got a fleeting glimpse and a mediocre photo) so I tend to call them all pill-bugs.  These critters are also known as woodlice and are part of the order Isopoda.  They’re not insects; in fact, they’re crustaceans, just like crabs, lobsters, and shrimp.  They help to decompose rotten wood and other decaying organic material, and need moisture to survive (hence are usually found only in damp, dark places – like under rocks).  The pill-bug (or whatever it was) quickly dashed into a crevice, but I was able to take a photo before it vanished.

Here’s a close-up:


One worm and the pill-bug were on the underside of the rock.  They conveniently posed side-by-side for me for a second so I could take a photo.  The other worm was in the soil below the rock.  And what about that dark shape in the top right of the photo?  I didn’t notice it when I was examining the rock and taking photos, but now it almost looks like it might be something alive as well.

I didn’t find much in my rock-flipping adventures, but I am happy with what I did find.  A different place and a different time of year (say, after a few days of rain) might lead to different results.  And I did learn that rocks like these are probably important refuges for creatures like pill-bugs in the hottest, driest days of summer.

Go out and flip some rocks, and who knows what you might find at the edge of the ordinary?


International Rock Flipping Day

Rock Flipping: Two Worms and a Pill-bug is part of International Rock Flipping Day 2014.  I’m hosting IRFD this year, and I’ll be posting the round-up of links tomorrow once most have come in.  If you’re participating, get your links to me as soon as you can!  Details and contact information are here.

This entry was posted in Ecology and Environment, Walking the Edge and tagged , . Bookmark the permalink.

5 Responses to Rock Flipping: Two Worms and a Pill-bug

  1. The dark thing on upper right is probably some sort of beetle. I can see 3 legs on one side, a separate head, and a squarish body. Then again, with that description, it could be a fly of some kind.

    It’s been dry here, too; I flipped dozens of rocks with nothing under them but baked dirt before I found a shady spot where the dirt was just toasted instead.

    • Heather says:

      I’m still not entirely convinced that it’s not just a blob of mud, since I find it hard to believe that I would have missed it the first time. But, yes, let’s say it’s a fly or beetle; that would bring my total up to 4 critters instead of just 3!

      And I’m glad to hear that it’s not just me who had trouble finding anything :)

  2. Sara Rall says:

    Just found your blog from Wanderin’ Weeta and very much enjoying it. To tell a pill bug (which can roll up) from a sowbug (which can’t), look at the back end. If it has two “tails” that stick out you have a sowbug (which would be my guess in the photo, but I can’t really see well enough to be certain).

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