As I recall, it seemed to be a blown-up tarantula, but it was so long ago.

BTW, that is definitely not the woman. As stated earlier, I thought the scene was in WHEN DINOSAURS RULED THE EARTH, after everything began to turn to ****, & the village was destroyed, the one girl stepped into [very quick] quicksand, the guy reached in & groped around trying to retrieve her, etc. My memory had it that it was then, that the cave girl ran into the webbed area. Though it is likely that this is a case of confabulation.

on another topic, one of my very favorite Moon movies is the one with the rock monsters shaped like Gumby.
