A casemaking clothes moth caterpillar crawls around partly surrounded by its long, lumpy case. Now scientists have found a caterpillar case (not this one) that incorporated hair from a nearby abandoned human body. Using the DNA in the hair can help invest

Clothes moth caterpillars may be a nuisance for your wardrobe, munching holes through sweaters and socks. But the pests don’t just eat clothing, they also feast on human hair. And though that may not sound as tasty as a glass of milk and cookies, the insects’ ghoulish appetite could help detectives who want to identify dead bodies.

Just like butterflies, casemaking clothes moths, Tinea pellionella, start as caterpillars. They transform to their moth namesake later in life. These insects are known best for the holes they leave in wool garments. But scientists have known that clothes moths also dine on dead animals in the wild, according to entomologist Sybil Bucheli of Sam Houston State University in Huntsville, Texas. “They had to eat something before people invented wool sweaters,” Bucheli said.

Now, though, Bucheli is showing how to use the moths’ leftovers as a forensic tool to solve mysteries. Little stubs of hair chewed up by a clothes moth caterpillar contain enough DNA, or genetic material, to identify the person the hair came from. That can help police sleuth out the identity of dead bodies, or even figure out where a person died.

To keep cozy and safe, the clothes moth caterpillar builds itself a case of woolly fibers and hair. The caterpillar burrows inside the case, dragging it around while feeding. The insect pokes its front end out to eat, growing bigger by the day. To adjust, the caterpillar expands its case with snips of hair and fiber found along the way.

Once it’s time to change into a moth, the caterpillar shuffles off into an out-of-the-way place and sheds the woolly case. The new moth may fly away, but it leaves its cast-off case behind.

And that’s precisely what forensic scientists could use to put a name to a dead body. These cases have enough bits of DNA-carrying hair that police can determine the identity of the person the hair belongs to — even if the person’s body gets moved to another location, away from the caterpillar’s case.

Already, the moths have showed their worth in a real case. They collected enough hair for DNA testing from an unlucky person found dead in Galveston County, Texas in 2007, Bucheli said.

Going Deeper:

Scientists have found a way to use hair to figure out where a person is from and where that person has been. The finding could help solve crimes, among other useful applications.

Water is central to the new technique. The liquid makes up more than half an adult human’s body weight. Our bodies break water down into its parts—hydrogen and oxygen. Atoms of these two elements end up in our tissues, fingernails, and hair.

These maps illustrate how the concentrations of certain hydrogen isotopes (top) and oxygen isotopes (bottom) in water differ throughout the United States. Red areas are where concentrations of these isotopes are highest. Blue points to regions having the

Proceedings of the National Academy of Sciences

But not all water is the same. Hydrogen and oxygen atoms can vary in how much they weigh. Different forms of a single element are called isotopes. And depending on where you live, tap water contains unique proportions of the heavier and lighter isotopes of hydrogen and oxygen.

Might hair record these watery quirks? That’s what James R. Ehleringer, an environmental chemist at the University of Utah in Salt Lake City, wondered.

To find out, he and his colleagues collected hair from barbers and hair stylists in 65 cities in 18 states across the United States. The researchers assumed that the hair they collected came from people who lived in the area.

Even though people drink a lot of bottled water these days, the scientists found that hair overwhelmingly reflected the concentrations of hydrogen and oxygen isotopes in local tap water. That’s probably because people usually cook their food in the local water. What’s more, most of the other liquids we drink—including milk and soft drinks—contain large amounts of water that also come from sources within their region.

Scientists already knew how the composition of water varies throughout the country. Ehleringer and colleagues combined that information with their results to predict the composition of hair in people from different regions.

The new technique can’t point to exactly where a person is from, because similar types of water appear in different regions that span a broad area. But authorities can now use the information to analyze hair samples from criminals or crime victims and narrow their search for clues.

“This [technique] doesn’t allow you to find the needle in a haystack, but it reduces the size of the haystack,” says Wolfram Meier-Augenstein, an analytical chemist at Queen’s University Belfast in Northern Ireland.

For example, one hair sample used in Ehleringer’s study came from a man who had recently moved from Beijing, China, to Salt Lake City. As his hair grew, it reflected his change in location.

Based on the finding, Jurian A. Hoogewerff, a chemist at the University of East Anglia in Norwich, England, offers this advice: “If you’re a criminal, shave.”

Going Deeper:

Perkins, Sid. 2008. Hairy forensics: Isotopes can identify the regions where a person may have lived. Science News 173(March 1):131. Available at http://www.sciencenews.org/articles/20080301/fob1.asp .

The spider “almost fell right on me,” says Autumn, who was lying in bed at the time. “I was terrified.”

Once he got over his fear, Autumn started to think about what he had seen. How did both creatures manage to defy gravity and walk on ceilings? And why was the gecko so much stickier than the spider?

A gecko has feet that can grip glass, even when the gecko is upside down.

K. Autumn

Autumn happened to be a gecko expert, based at Lewis & Clark College in Portland, Ore. So, when he came home from Hawaii, he turned his attention to the gravity-defying feats of the little lizard-like creatures.

Six years later, Autumn and his coworkers think they’ve cracked the secret of how geckos stick to surfaces, no matter how smooth. Their work contributes to a growing list of discoveries about spiders, frogs, flies, and other sticky wall-crawlers.

Together, the research could inspire a new generation of super-sticky materials, with applications from medicine to engineering. Some day, you might even use “gecko tape” to walk up walls.

A sticky mystery

People have been fascinated by geckos for thousands of years. In ancient Greece, the philosopher Aristotle wondered how the reptiles could walk upside down. No one had a good answer for him.

Even when scientists got into the act in the last 150 years, they still had trouble cracking the gecko’s secret. Step by step, however, they did manage to narrow down the possibilities.

Originally, some scientists thought that geckos might make a kind of glue to coat their feet. Many insects produce a gooey ooze that allows them to stick to waxy leaves. But geckos don’t leave sticky tracks, so this theory couldn’t be right.

In 1939, a German scientist showed that geckos can stick to glass even when all the air has been sucked out. This finding disproved the idea that the animals might have suction cups on their feet.

Likewise, water doesn’t affect a gecko’s stickiness, which nixes the suggestion that a type of static electricity enhances its grip. Static electricity, which works best under dry conditions, is the kind of force that allows a rubbed balloon to stick to a wall.

The first significant clue came just a few years ago. Geckos have millions of microscopic hairs, or setae, on the bottom of their feet. Autumn’s group used a special microscope to take a closer look at a single hair. “Each hair had a really bad case of split ends,” Autumn says. In fact, a single hair could have hundreds of bristles.

A single hair, or seta, on a gecko’s foot splits into hundreds of tiny bristles, or spatulae.

K. Autumn, E. Florance

The researchers suspected that these hairs might be the key. They used special sensors and microtweezers to analyze the setae, one at a time. Their work revealed a few surprises.

First of all, the hairs aren’t sticky by themselves. “We tried for months,” Autumn says. But “we couldn’t get them to stick until we measured how the gecko really moves its feet and toes. The secret is mechanical.”

Simply pushing the setae onto the surface and dragging them forward a tiny bit makes them stick, the researchers found. Just increasing the angle at which a hair touches a surface then allows the hair to pop off. In effect, a gecko peels off its feet just as you would peel off adhesive tape.

It’s really the size and shape of the tips of gecko foot hairs that matter most. At the right angle and pressure, a single hair can lift the weight of a large ant. A whole gecko’s worth of setae could lift the weight of a child.

Ceiling walkers

Autumn has focused on geckos partly because they are the biggest type of animal that can walk on ceilings. Some of the 850 species of geckos can grow to be as big as iguanas.

Other scientists are taking a broader approach. Around the world, teams of biologists, chemists, physicists, and engineers are using different strategies to understand how a variety of animals might stick to slippery things.

One group in Germany, for example, recently looked at setae in many different creatures that varied in size, from beetles and flies to geckos and spiders. The heavier the animal is, they found, the smaller are its hairs. A beetle’s hairs, for instance, are about a tenth the width of a human hair. A gecko’s hairs are one-fiftieth the size.

“Spider-Man would need hairs that are another factor of 10 to 20 smaller than the gecko’s,” says Ralph Spolenak, a materials scientist from the Max Planck Institute for Metals Research in Germany, who participated in the research. “This is much smaller than anything found in nature so far. So, it’s very unlikely that you will happen to run into Spider-Man down the hallway.”

However, scientists could develop materials that copy what gecko hairs do.

That’s exactly what Autumn and his colleagues have done. To test their theory about gecko adhesion, the researchers designed several types of “gecko tape.” So far, the resulting tape has been sticky, but not nearly as sticky as geckos are on their own.

Researchers continue to work towards making better versions of gecko-inspired tape, with plenty of exciting applications in mind. Think: ouch-less Band-Aids, robots that can climb walls, delicate surgery on one blood vessel at a time, and more.

Eventually, after a lot more work by scientists and engineers, you might even be able put on a pair of gecko gloves and gecko socks and hang out on the ceiling for a while.

“I imagine every one of you has at least once dreamt of being Spider-Man, looking at things from a different perspective, not being subject to everyone else’s constraints,” Spolenak says. “Just being Spider-Man for a while would definitely be very cool.”

“Forget Spider-Man,” Autumn says. “Think Gecko-Girl instead.”

His 7-year-old daughter, Kendra, has already asked to be first in line. Who wants to be number two?

Going Deeper:

News Detective: Emily goes rock climbing

Additional Information

Word Find: A Gecko Defies Gravity

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