Bug News Roundup: Ant Rafts, Robot Caterpillars

Drop a clump of fire ants into water and they will assemble into a raft that stays afloat for weeks, according to a new study. Plus, a new soft-bodied robot is modeled after caterpillars that curl up and roll away from predators without joints. SciFri's "Pick of the Week" turns to insects and engineering this week.

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IRA FLATOW, host:

I'm Ira Flatow. This is SCIENCE FRIDAY from NPR.

Now, with that out of the way...

(Soundbite of laughter)

FLATOW: Speaking about bugging, Flora is still with us here. And our Video Pick of the Week has to do with bugs, right?

FLORA LICHTMAN: Yes. Yeah. We are just up on the bug beat. We're not going to let you miss one bug story.

(Soundbite of laughter)

LICHTMAN: So this week, top of the bug news is a study about how fire ants - if you take a sort of glob of them and stick them in water or, let's say, their nest floods because it's really rainy, they form together - they join together and form a raft that they can float, sail on for weeks.

FLATOW: I couldn't believe this. I saw...

LICHTMAN: I know.

FLATOW: ...I didnt even know ants could do this.

LICHTMAN: Me neither.

FLATOW: But then, you show that it - that somebody sort of...

LICHTMAN: A graduate student.

FLATOW: ...of course, dumps a whole bunch, it must be hundreds of ants in some water, and instead of flowing down and drowning, they create this beautiful circle raft.

LICHTMAN: That was the other thing that's so amazing. It's not just kind of a motley raft. It turns out that it ends up being the sort of perfect circle. And it happens - this is what the researchers are looking at. Can you look at the ants' individual movements and figure out how they create this, you know, because they don't really know what's going to the ants' minds.

FLATOW: Right.

LICHTMAN: But it turns out if they move randomly and then when they hit the edge they stop moving or they turn back, eventually, through sort of the law of averages, you get this beautiful circular raft. And it carries these passengers for weeks. And it turns out, you know, I was curious, how do the ants breathe under water because some of them are submerged, right?

FLATOW: Right.

LICHTMAN: So part of what keeps the raft afloat and allows these ants to breathe is that there are air bubbles trapped between the ants' bodies, so they can sort of sneak a breath here and there.

FLATOW: Wow. It's just - it's amazing. And then the other part of your Video Pick of the Week has to do with...

LICHTMAN: Caterpillars and robots.

FLATOW: Yeah. What a combination.

LICHTMAN: I know. You wouldn't think - the best part was the researcher, Barry Trimmer, was like, you know, it's weird that we're looking at caterpillars, which don't move that much, to make a robot move. But caterpillars have a few tricks for getting away quickly. They can roll up then kind of shoot away like a wagon wheel. And you can see that happening on the video.

And he's interested in making a class of soft-bodied robots, robots that don't have hard parts. And the advantage is that they can sort of inflate or deflate. They can - they could go through tiny little holes. So if you're trying to navigate complex terrain, or let's say you're the Mars rover and you get your wheel stuck in the sand, you could just change your shape and get out.

FLATOW: Right.

LICHTMAN: And that's the sort of advantage of figuring out how to make these soft bodies move, which is not trivial.

FLATOW: No, it isn't. And you show how the caterpillars can squeeze through those little places. And it's up there on our website, on our Video Pick of the Week, up on - the usual left side on our website. And there, you know, the ants making these rafts, which I still can't believe.

LICHTMAN: They're amazing engineers.

FLATOW: And how they, you know, and how do they know how to do it in unison? You know, it's things about all of these colony, sort of insects.

LICHTMAN: These social insects, they...

FLATOW: They just - together, without any sort of - how does they communicate with one another to say, build that raft, get it circular and everybody do it?

LICHTMAN: Yeah. I mean, it was - I asked, how do they know? Who's in charge here? And, you know, of course, no one knows how they know how to do it, but it does seem to be an adaptive strategy to deal with - they hail from the rainforest, where it's rainy. And this is how they survive.

FLATOW: Great video. It's our Video Pick of the Week, up there at Flora Lichtman's creation, up on our website at sciencefriday.com. Watch those ants build a raft, and watch this robot caterpillar, a double header.

LICHTMAN: And you can do the ant experiment yourself, it turns out.

FLATOW: You can?

LICHTMAN: Get some gloves, first of all, find a fire ant nest - this is what the researchers said.

FLATOW: Find a fire ant nest?

LICHTMAN: with your gloves on.

FLATOW: Carefully.

LICHTMAN: Carefully. Dump them in water and you'll see for yourself.

FLATOW: Yeah, but under supervision. Thanks, Flora.

LICHTMAN: Thanks.

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