The girls took some time to adapt, but did eventually start spinning webs. The trouble is, the webs were not the right thickness - too thin in places and too thick in others. They failed to catch the (rather measly) one house fly that they were given to eat. I guess they were meant to share. (They did give them some rare steak, but did they ask if they were vegetarians first? I don't think so.) The scientists (they were men by the way) broke the first web so that Arabella and Anita had to build again, which they failed to do on the first day, but did on the second. Ultimately, they died, probably of dehydration. They might have intended to give them some more water, but probably had to go do something important like somersaults for the camera instead.
Normally, the silk that spiders weave has the same tensile strength as steel. It appears so fine and fragile to us, but on their scale, it's holding up the Forth Road Bridge. (Sorry - Bristol Suspension Bridge - I went to university in Scotland.)
It ocurred to me a few years ago that the silk threads are a metaphor for many women that I know and have known over the years. At first glance, they appear to be fragile. In an unatural environment, say a hospital ward,or frenetic office, with 1001 other things to do at home, the strong material they are made of is like the silk spun by the spiders out in space - too thin in places and out of shape.
Given a natural environment and a centre of gravity in line with the earth's and they can regain that strength that is in the DNA of every woman. How else would our species have survived?