Find me some bugs. And make sure they have six legs!" bellows Stanford University ecologist Nate Sanders. Ten ninth-graders from East Palo Alto, California, scatter across the San Francisco peninsula grasslands, swatting each other with butterfly nets. A girl looks at her watch in misery, but two boys race off gleefully. "I got one, I got one!" yells Miguel Chavez, clad in baggy rip-stop pants, a mesh "Mexico" jersey, and a red and green bandanna stretched across his forehead. Something blue-green flails in the net as he hands it over. "Ooh, a dragonfly," says Nate, inspecting the five-inch iridescent creature through the gauze. "This guy is one of the oldest members of the whole insect world. To catch a dragonfly, that's really nice."

Miguel blushes. The insect buzzes helplessly as Nate pulls it out of the net, holding it high, explaining how its dome-shaped eyes almost wrap around its head for peripheral predator vision. He asks two girls to come closer. The taller one wrinkles her nose and recoils. "That's not close," says Nate.

Though he's 27, Nate shares their childlike fascination-though not their revulsion-with bugs. Growing up on an Arkansas farm without cable TV or video games, he was shooed outside for entertainment. Ranging through the woods in search of big adventure-mountain lions and grizzly bears-he became obsessed with the tiny, bizarre world of insects instead. As the kids look closely at the dragonfly, Nate happily watches tough teenage attitudes slip away and a whole new sense of discovery awaken, just as it had for him.

A shriek pierces the air. Hopping backward from a gnarled oak, Amber Bundy points down. "Catch it, catch it! It's a potato bug!" All bravado, Miguel rushes to her rescue, scooping up a three-inch, striped insect with threatening jaws and a large, baldish head that looks eerily human.

"We have a winner!" says Nate, holding up the burrowing insect unaccustomed to sunlight or an entomologist's affection, its spiny legs cycling in the air. "This is a Jerusalem cricket. If it were our size, this thing would belong in that bar full of aliens in Star Wars." Nate sets the cricket down, and it immediately tunnels under the dirt.

"Every single person has to catch an insect and show it to me," commands Nate. "What makes an insect an insect? Are spiders insects? They have eight legs-so do ticks. Insects have six legs and three body parts-head, thorax, and abdomen. There are about 30 million species of insects in the world, a lot more than people-you should have no trouble finding one."

Miguel is off again, chasing something big and fast a hundred feet away. Five classmates follow. "Don't worry, it doesn't bite," says Nate, catching up. He looks more closely at the lizard. "Uh-it does bite. Do you have a glove?"

Miguel and Amber see no pretty dragonflies at home in East Palo Alto. An island of poverty in Silicon Valley only five miles from Stanford University, East Palo Alto lacks even a public high school. While elaborate stucco walls hide verdant backyard gardens in Palo Alto, rusty chain-link fences guard untended patches of soil in much of East Palo Alto, its arid atmosphere of dilapidated homes and liquor stores distant from the bustle and beauty of a forest ecosystem.

In a city where only one in three kids graduates from high school, Eastside College Preparatory School opened in 1996 to provide a rigorous, tuition-free education to 105 students. Its earth-science class visits Stanford's nearby 1,200-acre Jasper Ridge Biological Preserve eight times a year, studying a different aspect of nature each time. A grant from the Community Foundation Silicon Valley covers transportation, lunches, educational supplies, and stipends for teaching assistants like 20-year-old Stanford junior Zoe Bradbury, who masterminded these Jasper outings so Eastside kids could learn firsthand how living things rely on each other. "We start with how everything depends on the soil, and get into biological interactions that way," says Zoe.

Today's trip is a bug walk, a hands-on hunt for creeping critters that makes the dynamics of an ecosystem clearer than any classroom lecture could. "It's humbling to learn how these little creatures you squish between your fingers have an enormous impact on ecosystems," laughs Philippe Cohen, director of Jasper Ridge, after a recent bug ramble. These miniature wilderness adventures are catching on across the country, providing a bug's-eye view to families and curious adults as well as inner-city teens, allowing even the eco-elite to shed their scientific demeanor while peering in the grass on their hands and knees. "The chance to poke around with a purpose is important for many adults who would otherwise feel too self-conscious," says Ron Lyons, who has "bugged" for nine years at San Diego's Carpinteria State Beach. "And bug walks provide an opportunity for children to bring adults into their world."

At the Chicago Field Museum, bored birders are exploring the world another step down the food chain. In Lansing, Michigan, the Young Entomologists' Society offers bug walk how-to's, lesson plans, bug swaps, edible "insect" snacks like butterfly cookies, plus "Bugs on Wheels," a traveling minibeast zoo. North Carolina State University entomologist John Meyer uses bug walks to convert horticulture students who think the only good bug is a dead bug, and the Smithsonian's Gary Hevel gives racy prewalk talks about pheromone trails that get adults pretty excited. "They actually pay for the experience," Hevel boasts.

Kids, however, don't need much convincing; Nate just gets his young explorers on all fours looking for "anything small and weird" as he explains how the little things are more important than the big things-including people. Especially people. How do humans dominate ecosystems? By cutting down trees and putting up parking lots. Insects dominate nature in good ways, Nate explains-by decomposing dead matter, recycling nutrients into the soil, pollinating plants, and providing food for birds and other animals. Ants in particular are an ecosystem's movers and shakers, bulldozing even more soil than earthworms and performing the valuable service of deconstructing dead insects, birds, and mammals. "Imagine going out to get the newspaper with all that stuff still on the ground!" says Nate.

And unlike a $10 ticket to the San Francisco Zoo, bugging out comes at the low cost of just looking down. "People are attracted to big game, but those animals just stand around," says Nate. "There's drama and action with bugs. Nature's most voracious predators are wolf spiders and army ants, not polar bears." Army ants, for example, function as a "superpredator"-staging group raids to kill and dismember small mammals, lizards, and even baby birds many times their own size.

Nate peers at the ground beyond his magnifying glass, the portal to this Alice-in-Wonderland world. In a forest of thistles, ant troops carry off seeds and grass shreds, and pick apart a lizard carcass. Not quite dead, a termite struggles in an ant's jaws. A spider ambushes an ant soldier, tearing its head off but leaving behind the poisonous gland, like a child eating around the creamy filling of a Hostess Ho Ho. Nestled in the fork of a native grass, slender insects spin frothy homes, safe from predators and sunlight. Nearby, a Zarhipis beetle's furry black antennae sprout from its red head, while just beneath it a scrub jay snatches up an armored black beetle and flies off, the bug's legs irately churning on either side of the jay's beak. "NASA is trying to discover life in outer space," Nate tells the kids. "But we can just crawl around here and look at as wacky a world as any science-fiction movie."

Miguel has wrangled the foot-long, thrashing alligator lizard, his hand protected by a wadded T-shirt. It's fair game for a bug walk by virtue of the 20 western black-legged ticks it hosts. If one hooked onto Miguel, Nate explains, he'd be unlikely to contract the Lyme disease sometimes carried by ticks. The lizard's blood contains a substance-probably a heat- sensitive protein-lethal to the Lyme bacterium. (In fact, University of California, Berkeley, entomologist Robert Lane credits alligator and western fence lizards with reducing Lyme disease in the western United States.)

Cure-all lizards! Blue dragonflies with wraparound eyes! Star Wars aliens! The promise of more wonders sends everyone snaking down the forest trail. Although Jasper Ridge's redwoods were heavily logged in the 19th century, a cathedral-like oak canopy overhead still shades the cool, dark forest floor tangled with rotting logs and branches. Owls hoot across Searsville Lake, and Steller's jays hunt overhead. Nate touches a three-inch, gourdlike orb dangling from an oak branch that contains oak gall wasp larvae. When this tree produced new foliage, a wasp drilled into what was then a soft twig, depositing her eggs before the bark toughened. The tree isolated the wound with this scab-like gall, he explains, leaving the wasp an incubator and edible home for her offspring, which later chew themselves to the outside.

Frantically tapping Nate's shoulder, a petite girl with hair pulled back Audrey Hepburn-style daintily presents an ant on a leaf, extending her arm forward and her disgusted face as far back as possible. "This ant's from Argentina," says Nate, relieving her of the burden and spinning a tale of ant stowaways disembarking in New Orleans from a sugar or coffee ship in the 1890s. Migrating west, they forced out native ant species by out-competing them for the available food. Unlike the single-queen colonies of most ant species, the Argentines' hundreds of egg-laden queens make them virtually impossible to exterminate with the usual method of poisoned ant bait carried back to the nest.

In the early 1980s, the San Francisco peninsula (along with other large swaths of California) were sprayed from the air with the pesticide malathion in an attempt to eradicate the Mediterranean fruit fly. Jasper Ridge, however, was exempt from the spraying, leaving it an oasis of insect diversity. But as the Argentine invasion eradicates local ant species, Nate fears a ripple effect in this sheltered ecosystem when other creatures cannot find their preferred food source. (The Argentine ants are too minuscule for some animals to feed on.) The next species to go is anyone's guess.

Nate delicately squishes an Argentine ant on the end of his finger and says that like all ants we'll see today, it's female. Does anyone know why? "Yeah," nods Amber, poking at a male classmate. "After mating, you're DEAD!" She's right, Nate explains; fewer males than females of most ant species are created. The males die within three days after mating with the queen, and the annual event leaves dead ants everywhere right here at Jasper.

Amber looks through Nate's lens. On a thistle, a native Prenolepis imparis, or false honeypot ant, scurries around a tiny speck, stroking it with a leg, caressing it with an antenna. Then around to the other side of the light-green, pear-shaped speck-an aphid-for a poke. Another native ant races up the plant's stem, helping position the aphid to insert its needle-nosed proboscis into the leaf. A tiny golden drop appears from the aphid, and the honeydew-really aphid excrement-is swallowed by the second ant. The translucent substance is the ants' sweet symbiotic reward for tending and protecting the pest.

A few feet away, a column of false honeypot ants streams up and down the oak where the jays are hunting. The southbound lane is slower, the ants' abdomens swollen with tree sap. Their exoskeletons separate slightly, giving a tiger-striped effect. At the base of another oak, everyone is on hands and knees, mesmerized as an Argentine ant struggles with a dead beetle, while two more push, pull, and roll a torn-off white spider abdomen down a hole. When the Jasper hillsides turn brown in the summer, ant nests remain green, fertile with the spoils of scavenging. "They're the little creatures who run the world," says Nate, quoting Harvard zoologist E. O. Wilson. It's a biology-essay cliché, says Nate, that without insects, this would not be the world as we know it. With so many species, so much abundance, they provide every service-everything other animals do, they can do, and more. He turns to a girl pointing down at her bug du jour. "You gotta pick it up or it doesn't count."

"Oh . . . no . . ."

Farther down the trail, water thunders down 67 feet of stepped concrete into the San Francisquito Creek as the Eastsiders thread across the 1870s Searsville Lake dam. A stand of yellow mariposa lilies explodes below, while white Pieris butterflies flit just out of reach. Sunlight glitters off the marsh reeds, and a thick pillow of fog rests on the conifers atop the distant Santa Cruz Mountains. Nine banana slugs lounge in the shade, the air damp from the spray.

Joel Perez quietly tugs Nate over to an oak sapling. Atop a gently rolled leaf, a wasp is barely stuck in a few strands of silk. It tests one leg, then another, trapping itself more and more. One-tenth its size, a ghostly white spider peers from behind the leaf's curl with all eight eyes. This prey is too large to wrap and stun. It grabs one of the wasp's two remaining free legs. The spider pulls. The wasp counters. This tug-of-war continues for a few seconds until the wasp collapses backward into the tangled web.

A girl in a fluorescent-yellow parka makes a startling picture, offering a matching yellow banana slug, torchlike, on the end of a stick. That's not an insect, says Nate-but he's pleased that at least she's shifted her interest from an intense conversation about boys. Two girls watch soldier beetles mating, the male expressively raising his middle two legs on either side now and then. A few feet away, students find a striped yellow spider lying in wait, a furry green caterpillar feeding on a brilliant mule ear flower, and a honey bee pollinating an orange California poppy. On a bay leaf, a neon-yellow juvenile Mirid only a millimeter long resembles a miniature Pokémon, the base of its comical red-striped antennae visible deep inside its translucent body. Three girls squeal as a small cloud of gnats envelop them. Miguel's voice booms from down the trail. "Yuck! Look at this-it's like a plastic bag. Hey, hey, hey, Nate, come here!" Nate gently disperses the jellybean-size foam pouf to reveal a half-inch green nymphal spittlebug. "A whattlebug? What's this? Bug spit? There's a bug under all this stuff? For real?" The spit-nothing more than voided plant sap and "ooze," a viscous substance mixed with air-protects and humidifies these young insects as they feed on their host plant.

These minute observations are what Nate hopes the group carries home. "Sort of a trickle-down, they tell their friends and it snowballs, this information about something underappreciated," he says. It's about understanding biodiversity: careful observation showing why it's important to conserve every species.

Joel finds a western tussock moth caterpillar, tiled red, yellow, and black, with four gray tufts and a matching fringe of fur all around. It's almost feline, except for antennae-like projections and a tail resembling bunches of black enoki mushrooms. As Ogden Nash observed, the trouble with a kitten is that it eventually becomes a cat, and this flamboyant creature soon will metamorphose into a dull gray moth. Joel picks at something else in his net but crushes it. Nate leans over reassuringly to say that he'd be a fine scientist. Joel says he's planning to become president. How about being a scientist-president? "Yeah!" says Joel. "Like Thomas Jefferson."

Back at the docent center, nine of the teenagers cluster at two picnic tables. Their teacher, Monya Baker, breaks out sugary Mexican funnel-cake pastries. What have you learned? Nate is bowled over by the enthusiastic, accurate response. Ants are female, moths have hairy wings but butterflies don't, only insects have six legs, dragonflies' eyes wrap around their heads, there are more beetles than any other animal, spiders are mean!

Joel sits alone, scratching the sand with a stick. He's surprised that bugdom is so small and so busy. He didn't know bugs were so cool. Nate realized the visit was sinking in when Joel slowed way, way down-poking at leaf litter, finding smaller and smaller insects. The success of a bug walk is measured in how little territory is traversed. A really good micro-safari covers only 100 yards all afternoon.

Like Joel, Nate had his own transformative bug experience. In college, he was preparing to study physical therapy, but then came a taxonomic treasure hunt in a required zoology class. While turning over a rotting stump, his teacher whispered how lucky he was to be paid for doing this. Realizing he could make a career out of what he'd loved so much since rambling through the Arkansas woods, it was conservation biology from then on. As for Joel, Nate is confident that if he gets as excited about insects or anything else as he was today, he'll succeed at it easily.

The Eastside van rumbles away and a cloud of dust settles around the edge of the forest. Umber dusk filters through the oak canopy, dappling the ground. Out of the quiet, the trees crescendo with bird calls and an occasional cicada. A small snakefly lands on Nate's sleeve and a ground beetle climbs across his shoe. Everything we disturbed is closing in again. "After you've been here awhile, everything returns, as if it all gets used to you and you become a part of it," Nate says, as softly as humanly possible.