They placed cages in areas of natural vegetation and allowed some grasshoppers to be alone while others were placed in cages with a spider.
They glued the mouths of the spiders shut in order to make sure that the grasshoppers experienced pure fear, but were not actually killed by the predators.
…and thinking, Damn, but scientists can be d*cks sometimes. I know that science ain’t always pretty, but wow. Does PETA know about this one?