Question: How do insects stick to walls and ceilings? How can a spider scuttle across my ceiling without falling off?
Answer: The answer depends on the animal. Most small animals simply rely on their claws and minute rough areas or cracks in the surfaces that they walk on. Such creatures cannot walk up genuinely smooth and steep surfaces.
Some spiders can leave a sticky trail of silk wherever they go and use it much like a climber's rope, often with breathtaking sophistication. For example, some kinds of jumping spiders can actually use their line to leap on flies while both are hanging from the ceiling.
Various insects exploit the stickiness of substances they secrete, which is in turn due to the van der Waals forces between the sticky material's atoms. These substances range from the a layer of slime similar to that on which a snail glides, to a minute ...
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