The experiment was set up so that a spider, released by an astronaut (Owen Garriot) into a box similar to a window frame, would be able to build a web. A camera was positioned to take photos and videos of the webs and spider activities. This is the Skylab experiment cage, shown here during ground operations.
Three days before the launch, each spider was fed a house fly. They were provided with a water-soaked sponge in their storage vials. The launch took place on July 28, 1973. Both Arabella and Anita needed some time to adapt to near-weightlessness. Neither spider, kept in holding vials, voluntarily entered the experiment cage. Both Arabella and Anita made what has been described as 'erratic swimming motions' upon ejection into the experiment cage. After a day in the spider box, Arabella produced her first rudimentary web in a corner of the frame. The next day, she produced a complete web. Here is a photo of the first spider web spun in space:
These results prompted the crewmembers to extend the initial protocol. They fed the spiders bits of rare filet mignon and provided additional water (note: A. diadematus can survive up to three weeks without food if an adequate water supply is available.) On August 13th, half of Arabella's web was removed, to prompt her to build another. Although she ingested the remainder of the web, she did not build a new one. The spider was provided with water and proceeded to build a new web. This second complete web was more symmetrical than the first full web.
Both spiders died during the mission. They both showed evidence of dehydration. When the returned web samples were examined, it was determined that the thread spun in flight was finer than that spun preflight. Although the web patterns made in orbit were not significantly different from those that were built on Earth (aside from a possible unusual distribution of radial angles), there were differences in the characteristics of the thread. In addition to being thinner overall, the silk spun in orbit exhibited variations in thickness, where it was thin in some places and thick in others (on Earth it has a uniform width). The 'start and stop' nature of the silk appeared to be an adaptation of the spider to control the elasticity of the silk and resulting web.
Reference: Witt, P. N., M. B. Scarboro, D. B. Peakall, and R. Gause. (1977) Spider web-building in outer space: Evaluation of records from the Skylab spider experiment. Am. J. Arachnol. 4:115.