By all laws of physics, spiders as big and heavy as tarantulas shouldn't be able to climb walls or hang upside down—they should fall on their heads. But tarantulas do climb, albeit with difficulty, and researchers decided to find out how. So they collected the molted skins of several species of tarantulas, including the lead author's own dearly departed pet, Fluffy (pictured above). The bottoms of their fuzzy feet, it turns out, are covered with microscopic hairs, some of which serve as "spigots" for a sticky silk , which they only turn on when they start to fall. Since most spiders produce silk from spinnerets on their abdomens, the finding might help explain how spiders evolved so many uses for their silk, the researchers report in the June issue of The Journal of Experimental Biology. It also explains why tarantulas leave little silky footprints wherever they walk.
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