Do the wasps have some sort of suction cup, in which case, how do they regulate the suction to match their walking speed, or instead do they use a set of hooks on the base of their feet like velcro? If it is the latter, how do they “unhook” their feet without actually ripping their legs off (in case their hooks get stuck)? Or is it a completely different method?
They have thousands of small hairs on their feet. Here is a pdf file about it. The file also has some spiffy electron microscope pictures.
P.S.
Do not search for “insect feet” with Google. Yargh.
Geckoes do this too. They have ultrafine hairs on their toes, and make use of the molecular cohesion force to stick to walls and other smooth vertical surfaces.
To expand on QED’s explanation here a fascinating article on the specifics of the process.
On the same subject…
http://www.nature.com/nsu/030527/030527-11.html
“Inspired by geckos’ toes, a new super-sticky tape is so strong that it can stick a person to the ceiling by just one hand.”
A couple of Staff Reports that may be of interest:
How can ants walk on walls and ceilings?
How come geckos stick to the ceiling but centipedes don’t?
Here is a paper [.pdf document] which details the workings of the arolia mechanism, as described in the first of bibliopahge’s links.
Just yesterday I was watching a single tuft of dandilion fluff floating near the black plexiglas I was working on. The seed was gone, so the tuft was drifting on the breeze. It bumped the vertical plastic sheet and immediately adhered. I pulled it loose and let it drift close to the plastic, and it did the same thing again. It wasn’t visibly attracted to the plastic before it touched.
It’s chemical bonds, but at a scale where humans can watch it happen.
Think: why does adhesive tape stick to things? “Because it’s sticky” is not a good answer. Or ask a better one: why do most things NOT act like adhesive tape?