The scopulae are pads of bristles found on the pretarsus of all spiders. Each bristle has thousands of branched ends.
Van der Waals forces create a molecular Velcro, allowing tarantulas (and geckos) to readily crawl across walls and ceilings. A fine film of water further increases attachment capability.
Terrestrial tarantulas tend to have small scopulae that are used for grasping prey.
Arboreal tarantula scapulae (see below) appear as large pads, which allow individuals to rapidly run across vegetation high in rainforest canopies.
I’m looking forward to having my freshmen feel the difference tomorrow, when we begin discussion of arthropods!