Van der Waals force
When the scopulae are splayed out and placed against a surface, remarkable adhesion is produced due to the accumulation of adhesion of each individual setule interacting with a substrate. The adhesion may be due to the excretion of liquid from adhesive pads, although setae can adhere in both dry and wet modes. This enables spiders with scopulae to climb even sheer, smooth surfaces such as glass. The adhesion is so great that the spider could grip using this force and support 170 times its own weight. Possible physical mechanisms may include capillary, electrostatic, viscous, or Van der Waals force. (Niederegger et al 2002; Betz and Kölsch, 2004)