National Geographic : 2011 Nov
PHOTOS: DAVID LIITTSCHWAGER; CLAIRE RIND INSET An adult tarantula reaches thetopofa glass pane. NOW Tarantulas are among the largest, most primitive, best known spiders. Yet how these hairy crawlers negotiate steep, slippery surfaces has been a tangled web for arachnologists. Some say climbing tarantulas---too heavy and fragile to rely on sticky foot hairs as other spiders do---release silk from their feet when they lose their grip. Others insist silk comes only from abdominal spinnerets; the feet merely distribute it when a tarantula goes vertical. Enter Newcastle University biologist Claire Rind. This year she and her colleagues studied several species, including a Chilean rose (above) that they put in a glass tank lined with microscope slides. When the bin was tilted and jostled, the spider slipped but hung on. A video verified that only its feet had touched the slides, which bore silken footprints. The final test was a hard look at molted exoskeletons, whose feet had silk traces and what looked like nozzles among the setae, or hairs. Though some experts remain skeptical about silk-shooting foot spigots, Rind says she's pushing on. The next strands she hopes to unstick: whether nozzles exist on smaller or juvenile tarantulas---or even on other spider species. ---Jeremy Berlin Spider Spigots Seen through an electron microscope, a tarantula's foot has sticky hairs and what some believe are thin, silk-secreting spigots.