On the left, the first web built by the Larinioides patagiatus spider on the International Space Station in 2008. On the right, the first web built by the Metepeira labyrinthea spider partially destroyed Larinioides’ work. Photo courtesy of NASA

Weird things happen in outer space.

Weightlessness is, by all accounts, the strangest new world for astronauts. It’s a factor in everything from space sickness to disorientation to psychological disruptions, all complicated by isolation, close quarters and the risk of exposure to cosmic radiation. Astronauts describe difficulties judging distances and the sizes of objects. Sometimes simple mental operations, such as imagining the rotation of different objects, become problematic. And the weirdness can range into the vicinity of hallucinatory. Several crews of Chinese astronauts reported distinct knock-knock-knocking-on-the-door-like sounds, unexplained.

So, what would happen if you plunked spiders into that weird environment?

It’s been tried three times in the U.S. space program. The first try, in 1973, happened as the result of the Skylab Student Experiment Competition, which a high school student won by suggesting it might be interesting to see how spiders build webs in zero gravity. So they shipped two cross spiders, aka Araneus diadematus (which we have here in Maine), up to Skylab. One reason they were chosen is because cross spiders’ webs are normally very regular, even among orbweavers.

The spiders, which the astronauts called Arabella and Anita, indeed built five webs, four of which appeared unusually small and irregular. But in the end the webs could not be evaluated adequately because the astronauts for some reason took no photos showing an entire web. And somehow, no one thought to feed the spiders either, so there was no way to know if web construction was affected by sheer hunger and lack of prey.

In 2008 some arachnologists designed what they thought would be a better experiment (with food). Two spiders, a labyrinth orbweaver (Metepeira labyrinthea) and a young Larinioides patagiatus (close cousin of the furrow orbweaver and bridge orbweaver), shipped up to the International Space Station. (We have all these spiders in Maine.) Larinioides was supposed to be a sort of backup in case Metepeira died, so she started out life in space in a holding chamber inside the main box. Somehow, though, she escaped. This time there was a supply of fruit flies for the spiders to catch and eat. So the spiders started trying to build webs, which again was a serious engineering problem in zero gravity. But after a lot of flailing and experimenting, Elmo and Spiderman (as the astronauts called them) were building “awkward-looking, but stable spiral webs.”


Within a week, though, there was trouble. The webs were so close together that Metepeira’s webs were wrecking Larinioides’ webs. Meanwhile, the fruit flies were reproducing. Larvae and pupae started collecting on the observation window of the spider box. Within a month there was such a thick smear of fruit fly youth on the window that the astronauts could not see into the box, much less take pictures of the webs. Again, it was hard to tell with much certainty how the zero-gravity webs differed from the control webs on Earth.

In 2011, the arachnologists got a chance to try again. They sent to the ISS two golden silk orbweavers, Trichonephila clavipes (nicknamed Gladys and Esmeralda), chosen because their orb webs are markedly asymmetric. The golden silk orbweaver, a tropical and subtropical spider, builds very beautifully regular webs on Earth, with a hub that is noticeably off center, or asymmetric.

The golden silk orbweavers lived up there in space for two months. Once they figured out how to operate in zero gravity, they built nearly three dozen webs. This time the experiment incorporated 12-hour light and dark intervals, and photos made every five minutes showed that webs built in darkness tended to be symmetric, while webs built in light tended to be more Earth-typically asymmetric.

On Earth, Trichonephila like most orbweavers sits face down on her web. In the zero gravity of space, they tended to face down when the lights were on, but when the lights were off, they showed no tendency to face in any particular direction. This is all interesting because it implies that light, as well as gravity, is a factor to the spiders. This was all assessed from photos taken of the first two-thirds or so of the webs.

A lot of snipping, tightening and discarding goes on in spider web construction, leaving silk debris that on Earth is cleared away by wind, rain and other animals. Maybe there’s even more snipping and discarding of silk during the trial and error in zero gravity. I bet you can see where this is going. Soon there was such a buildup of discarded and leftover silk floating around inside the box that the cameras couldn’t get pictures of the last 14 or so webs the spiders built.

The space webs were generally less regular than webs built in Earth gravity, and the regularity of webs decreased during the experiment. The researchers thought the decreasing regularity could be due to the fact that the spiders did not have enough space to build as big as they do in wild conditions on Earth. Which is kind of ironic when you think about it for a second. They were, after all, in space.

They were up there for about two months. The female Trichonephila molted three times, which was a first. The male made it back to Earth alive, the first spider to survive the round trip.

No mention is made, of course, of what the spiders thought of all this, because no one knows if spiders even think, in the way we think of “thinking.” I wonder if they have difficulties judging distances and the sizes of objects and how the objects rotate or how weightless silk moves. They figure it out. It would be very weird to find out how.

Dana Wilde lives in Troy. You can contact him at naturalist1@dwildepress.net. His book “A Backyard Book of Spiders in Maine” is available from North Country Press. Backyard Naturalist appears the second and fourth Thursdays each month.

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