Why spiders dont stick to their own web, centuries old mystery solved

Researchers at the University of Costa Rica led by Daniel Briceños and William Eberhard tackle the very old yet never fully answered question of just how come spiders do not stick to their own webs.

This Research Snapshot comes all the way from Costa Rica, pura vida!

Researchers Daniel Briceños and William Eberhard from the University of Costa Rica and the Smithsonian Tropical Research Institute in Panama have figured out the ancient question of just how spiders avoid sticking to their own webs. To tackle this sticky question the authors repeated old studies, based on observations of the spider's behavior, using modern technology to precisely track down the web-weaving behavior of two tropical species, Nephila clavipes and Gasteracantha cancriformis.

Their findings were published in the April issue of the journal Naturwissenschaften and confirm some previous results, but also add new evidence suggesting that these spiders use three basic approaches to avoid sticking to their webs.

"...dense arrays of branched setae on the legs that reduce the area of contact with adhesive material; careful engagement and withdrawal movements of its legs that minimize contact with the adhesive and that avoid pulling against the line itself; and a chemical coating or surface layer that reduces adhesion.

Repeating old, widely quoted but poorly documented studies with modern equipment and techniques they discovered that spiders are protected both by a layer of branching hairs and by a non-stick chemical coating; spiders also know how to walk around, very carefully, in ways that minimize adhesive forces as they push against their sticky silk lines hundreds to thousands of times during the construction of each orb.

"We have shown that they were correct regarding a coating on the spider's tarsi, but that they were seriously incomplete in not appreciating the importance of the setae on the legs and the very careful movements of the spider that minimize the adhesion of lines to their legs."

Future research from this team is now focused on gaining more information about the chemical basis of the coating substances used by spiders, and to tackle another, even more complicated mystery.

"On the one hand, Daniel has begun work with chemists at the Univ. de Costa Rica to attempt to characterize chemically the coating substance or substances. Secondly, we have both spent time (so far without major advances) thinking about a different type of sticky silk that some spiders make, which is not based on sticky liquid droplets but many many extremely fine lines. The spiders that make this second kind of sticky silk also do not adhere to their own silk, and the mechanism of this is still a complete mystery."

Best of luck with this new research!

The Article "Spiders avoid sticking to their webs: clever leg movements, branched drip-tip setae, and anti-adhesive surfaces" is available here: http://dx.doi.org/10.1007/s00114-012-0901-9

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