They’re slaters, in the West of Scotland. No idea why.
Trilobite.
Pillbugs or Rolly-Pollys.
Sowbugs (or Salbugs, as I heard it) were the similar, but slightly larger and lighter gray ones that didn’t roll up into balls.
Ever since reading The Leaf Men and the Brave Good Bugs, I’ve also called them Doodlebugs, but I didn’t grow up with that name.
(Southern CA, but might have gotten the nomenclature from my Iowa/South Dakota grandparents.)
I use its correct latin scientific name: roly-poly.
When I was a kid, we used to have races with them.
They’re great bugs for kids to play with. They don’t bite, they’re not “dirty,” and they don’t even make a mess if you squish 'em.
Me too. Grew up in So Cal.
Ah well I’m not surprised by anything from the land of the choochter and the tatty bogle. 
Pill bug.
This being like, a critical question, I wonder why I am not allowed to vote in the poll. Did it expire in less than four hours? Am I not accepted on the bug-naming protocols approved by the Perfect Master? 
When our daughter was little, she always called them ball bugs. So, we stuck with that. We still call them ball bugs some 20+ years later.
I grew up in San Diego. I knew “sow bug,” “potato bug,” and “pill bug,” but I called them sow bugs. I never heard roly-poly growing up, by far the most common now. We also had the abomination of real potato bugs, linked upthread, but I never knew a name for them.
Why are they called “sow bugs,” anyway?
Pill bug in the picture. Sow bug is the kind that look similar but can’t roll. Wood louse I know is the scientific term that nobody really uses. I’ve never seen a pill millipede to my knowledge. It’s okay to call them rollie-pollies… if you’re four. Seriously though, that name annoyed me even as a kid.
Doodle bug is not a word I’ve ever heard used where I’m from, but I understand it as referring to ant lions as well.
AngelSoft, you’re beginning to make me regret installing the SDMB Greasemonkey image script. Damn potato bugs…
Then you’d get the pill/sow bugs who were purple, presumably from some toxin. And sometimes you’d find one with hundreds of writhing young clutching her underside…
That is a sow bug, which is different from a pill bug. Sow bugs are larger, and don’t roll into as tight a ball as a pill bug.
This is what we called a potato bug.
Southern California.
Once I was helping to fix up a house and when we were working on the porch, I suddenly heard a group scream. “Aagh! Is it poisonous? Is it poisonous?” I turned around, and looked at what a half-dozen people were pointing at.
It was a pill bug. I told them it wasn’t poisonous. I hope I was right. Nobody died…that day.
Woodlouse, Pill bug, Roly-poly, though I’ve heard Sow bug too.
Roly poly, occasionally pill bug.
Potato bug? interesting, that was what we always called these guys. Which I now see is officially called a “Jerusalem cricket”.
Huh, so that’s where the name comes from. I thought it was from being brown and squishy looking.
For some reason I can’t even figure out, we call those things “water bugs”. They don’t show up in the water, they don’t have anything more to do with water than any other bug, but that’s what we call them.
Water bugs to me are generally Nepomorpha, but more specifically these creepy fuckers. Who can bite. Hard. I don’t know if I’ve ever actually seen one though, don’t think they were native, but never used the term for water boatmen, backswimmers, or water striders I did see.
I guess “water bug” is also used for cockroaches. While vacationing in Florida, I had a damn American cockroach (the bigger ones) drop on me in the shower. I am not ashamed by my shrieks!
“Cute!” should be a poll option.
I actually have a creepy ass story about those little buggers. In the late 90s, I worked for daycare centers. One day, someone found a potato bug and thought it would be neat to show the kids. Now, these kids were all about 2-3 years old. We had an insect cage that someone had made out of window screen material. And it wasn’t the normal type that tears easily. They had made it out of the thick stuff that’s really strong. So we had it in the cage, and showed the kids. It was about naptime, so we set it off to the side and planned to release it after nap was over. Well, nap time’s over. We go to get the bug. It’s gone. Little fucker had chewed a hole right through the screen mesh and was somewhere in the room. We never did find him either.
And for the love of god. Never. Ever. EVER step on one. The sound plus the sensation of them being crushed under your shoe on top of the resulting mess will give you the squeebies for days to come.
Aussie here. Pretty much everybody calls them slater bugs. Kids sometimes call them rolly pollys