WIKIMEDIA COMMONS, TECHUSER
You can’t tiptoe past a spider this Halloween. It will detect even the tiniest vibrations, according to a new study published in the Journal of the Royal Society Interface.
An adult female Cupiennius salei, the Central American wandering spider, has more than 3,000 slit sensilla, or strain sensors, on its body. Located mostly on the legs and near the leg joints, the sensors can detect vibrations in the surrounding substrate, helping them to catch prey even in the dark of night.
The sensilla are comprised of minute parallel slits. Nearby vibrations result in physical forces that compress and stimulate the sensors. Clemens F. Schaber of the University of Vienna and his colleagues used powerful optical and micro-force measurements and found that the sensory organs responded to forces as small as 0.01 milliNewtons—less than half a percent of the body weight of a typical cockroach.