The University of Bristol created a wonderfully informative animation that explains how spiders use static electricity in the atmosphere to set themselves aloft. This process is known as ballooning and according to an experiment conducted by Erica L. Morley and Daniel Robert, it can only occur when the weather and the electrostatic levels are just right.
In our lab at the University of Bristol we isolated spiders from any airflow or atmospheric electricity and generated our own controlled electric field at levels found in nature. In response, the spiders began to change
their behavior to perform ‘tiptoeing’ where they straighten their legs raised their abdomen, and released silk. This behavior is only ever seen when a spider wants to balloon.