Arachnophobics Beware

The story contains big, hairy spiders. And they don't like to be told what to do.

By Matt Jennings

The Chilean Rose Hair Tarantula is one nasty looking arachnid.
Classified as a “moderately large” tarantula,

it has legs like crooked pipe cleaners, a bulbous abdomen, and a fused thorax and head; covering the whole thing is a coat of reddish fuzz. But what really sends chills up the spine is when the creature decides to go for a stroll. Its eight legs move as if it was being choreographed by Wes Craven, each appendage moving independently from the others, with those on opposite sides of its body alternating steps.

“That unusual creepy walk that freaks so many people out?” says biology professor and neuroscience program director Tom Root to the students in his Animal Behavior course. “That combination of movement is called the gait. That’s what we’ll be studying.” Specifically, the class will be studying the neurobiology of locomotion in an attempt to understand neural decision-making in the tarantulas. Root outlines the basic neural circuitry—brain, nerve cord, interoceptors, exteroceptors—involved in the instantaneous decisions the spider must make as it moves. “The task for a tarantula’s brain,” he explains, “is to keep its eight legs moving, not in a random way, but in a very specific way.” The students’ task, then, will be to record a spider’s specific gait, indicating which legs move when, first in a controlled situation and then in an experiment that will spatially challenge the creature. Of course, to do so, the students will have to handle the tarantulas, which, not surprisingly, has some folks spooked.

So as 25 men and women look on—with expressions ranging from disgust to fascination—Root begins to explain that there are direct and indirect methods of handling the spiders. Indirectly, one can use a flat substance (cardboard, slate) to scoop a specimen from its terrarium into a Tupperware-like, circular holding chamber.  From there, the chamber can be tilted onto its side, and the spider can be coaxed to move along into a “walking chamber,” a clear plastic rectangular structure about the size of a shoebox. Once in the walking chamber, the spider can again be coaxed to walk the length of the box; there’s not a top on the box, and a pencil or thin watercolor paintbrush can be used to prod the spider. (It usually takes just one poke, Root says.) It’s during this stroll that the students videotape the tarantula’s gait; later, they’ll review the tape to observe and record the order in which the legs moved.

Now, Root says, there is also a direct method of handling a tarantula. All you has to do is allow it “to walk onto your hand.” But, he adds, “you don’t want to grab it. Leave the choice up to him.” As the students scatter in pairs to their respective workstations in the lab, a few brave souls are willing to go the direct route.

“Oh man, this is so cool; it’s barely touching me,” says one woman. Next to her, looking a little less confident, a guy is allowing one of the tarantulas to creep onto his hand. And right then, his lab partner bounces over and announces, “Root says that yes, they are poisonous, but no, they won’t kill you. But if you get bitten it will hurt like hell.”

“Oh my god. Will someone please take this spider back?”

Tarantula #10 (let’s call him Boris) is not doing what Ian Drummond ’09 and John Havel ’09 want him to do.  Two weeks have passed since Drummond, Havel, and the rest of the animal behavior class conducted their control experiments with the tarantulas—videotaping their gaits, observing said tape, and recording the results. In the interim, the students have been designing experiments that will challenge the spiders in their walking environment. One pair has placed a foamed egg crate in its walking chamber; another has scattered twigs and grass on the floor of its chamber. The purpose is to see if the spiders will adjust their gaits in order to navigate the new terrain.

Drummond and Havel want to see how tarantulas step across gaps—they hypothesize that the spiders’ gaits won’t change—and to answer their query, they have fashioned a one-and-a-half-inch gap by placing two blocks of wood in the chamber. The blocks have identical heights, so the spider will be walking across a relatively level terrain. The widths are the same, too; there are no gaps between the edge of the wood and the wall. Each block covers about half the length of the walking chamber. Almost, but not quite. And there’s that gap, the inch-and-a-half expanse between the blocks.

Boris, though, doesn’t want to step across the gap; he finds it easier to just climb down into the space between the two blocks and sit there. Drummond and Havel narrow the gap to one inch.

Down goes Boris.

“Oh, come on,” says Drummond.

“What if we stack two more blocks on top, doubling the height?” Havel suggests. The idea is that the drop would be significant enough that Boris won’t have a choice but to step across.

But Boris does have a choice . . . and down into the gap he goes.

They try it a few more times with the same result. “OK,”  says Drummond, “let’s try a new spider.”

A few minutes later, spider #24 (we’ll call her Natasha for the sake of the narrative) is introduced into the chamber. She spiders along the first block of wood, reaches the gap, begins to stretch a leg across, and then slowly steps . . . down. Into the gap. They try again. Same result.

Root stops by and has an idea. “What if you were to take two terrariums and place them almost end to end, separated by about an inch and a half. Then place two walking chambers on top of each.” The terrariums are about a foot tall. Surely Natasha wouldn’t want to drop that far.

She doesn’t. But she doesn’t want to step across the gap, either. She simply stops at the edge of the chamber. When Drummond gently prods her with the thin end of a fluorescent green paintbrush, Natasha takes offense.

All eight of her legs seem to move at once (though intellectually we know that’s not the case) and she lets out a hiss.

“Jesus,” Drummond yells, jumping back from the table. “I think it grabbed the brush. I’m sweating. That scared the hell out of me.” His face is as red as the T-shirt he’s wearing.

“Let’s try a new spider.”

Havel returns Natasha to her terrarium and returns a few seconds later with spider #9, a huge, hairy creature. Let’s call her Shelob.

“She’s a monster,” mutters Drummond. “John, you can do this one.”

Drummond and Havel are now trying a different approach. They’ve placed the two walking chambers directly on the lab table, leaving a quarter-inch gap between the two. Root likens it to creating a puddle for the tarantula to step over. But, like her friends, Shelob wants no part of it.

Drummond and Havel are now an hour-and-a-half into what has proved to be a fruitless experiment. Not one spider has cooperated, and to conduct the experiment properly, the students would have to run three trials—with ten different spiders.

“Maybe we need a new experiment,” Havel says.