Though spiders and their leg hairs are generally creepy to most people, they are actually very interesting. The hairs found on many Arthropods, like spiders, are called Setae which are bristles protruding from the spiders’ tough outer layer called a cuticle. What is amazing about these leg hairs is that they can do everything from allowing them to walk upside-down or on water, sensing touch and temperature, gravity and acceleration, even equivalents of hearing and taste. Because spiders don’t have ears, they can “hear” you with their leg hairs, called trichobothria, from the pressure waves created from flying insects, and others can sense tiny vibrations in the ground to help locate walking prey. Other setae branch into smaller bristles called setules, which increase the effects of two forces—“capillary adhesion” and “van der Waal’s forces”—allowing spiders to climb on walls and smooth surfaces just like the gecko. These setules are numbered in the thousands and are each tipped with spatula fibers which are almost as small as the wavelength of visible light! Similar hairs allow them to “walk on water” but in this case the hairs are coated in super-hydrophobic wax and are bumpy to increase surface area, allowing them to essentially be pushed up to the surface by the water itself. Spiders are missing the sense of taste in their mouths as well, but they are still able to taste things because their leg hairs are sensitive to chemicals. These hairs come into contact with whatever the spider is interested in, whether it be food or a potential mate, and “tastes” the object. A similar process goes for smelling; in this case chemicals floating in the air are “smelled”. Think of that the next time a spider is on your wall—it’s not just looking at you.
Guest article written by Brian Devonshire (thesciencellama.tumblr.com)
(Image Credit: 1, 2, 3)