Disgusting bugs weave magical fabric threads
The process is labor intensive.
The unsung hero of the silk industry is the 3-inch long Bombyx mori moth caterpillar as thick as a human finger. Unlike the glamorous silk it produces, this creature is downright disgusting.
"Silk is produced by spit from the caterpillar's mouth," says Jill Graham of the Butterfly Pavilion in Westminster, Colo. "Their salivary glands are just gigantic, about a tenth of their body weight when they are ready to spin."
The caterpillars spend most of their time eating, she says. In three to four weeks, they go from hair-like hatchlings to swollen, three-inch-long caterpillars more than 10,000 times their original weight.
Graham became a silkworm wrangler for six months, raising cocoons from eggs to learn more about sericulture, as the silk industry is called. First, she obtained some tiny steel gray eggs from a scientific supply company. After they hatched, she transferred the almost invisible brood one at a time onto a pile of mulberry food, using a jeweler's magnifying goggles and a paintbrush.
"You have to move them every day to the new food," she says. After 4,600 years of breeding by humans they have lost their ability to crawl.
Time to spin
Once mature, Graham placed each caterpillar into a piece of toilet paper tube. There they began busily spinning silk around themselves in figure eights until they disappeared under a downy coat of white.
"The cocoon is for protection," she says, "like silk long underwear. It's light and really good insulation."
Later, Graham boiled the cocoons in water, donned her jeweler's goggles again and began unspooling them by hand, winding the strong filament around an index card. Two and a half hours later, she had little to show. The yards of thread were barely visible. So Graham taught herself to unwind a dozen cocoons at a time.
Graham's experiments hint at the immense size of the silk industry and the labor required.
"It takes 1,700 caterpillars to produce a pound of silk," she says. "And those cocoons take 10 hours to unwind by machine."