BZZZZZZZZZZZ. You hear them before you see them. Nine large bees, antennae bobbing, meander down a narrow trail, stopping to examine a stream, a flower, a hollow tree. It's enough to make you run for cover -- at least it would be if the bees would stop yanking each other's antennae and demanding that their parents pick them up and carry them.

The group of buzzing 2- and 3-year-olds is gathered for "To Bee or Not to Bee," one of six nature programs in Discovery Creek's Toddler Treehouse series. The children's museum offers a wide variety of environmental-education programming for kids, including those still in diapers. Toddler Treehouse, one of three Discovery Creek series designed for the very young, was launched in 2000. At the time, says marketing director Jessica Fraser, there were few programs in the Washington area for toddlers.

The same is true today -- especially for kids younger than 3, the minimum age for many children's activities.

Discovery Creek's classes are held at the museum's Historic Schoolhouse location on MacArthur Boulevard in Northwest Washington. The building's snug 19th-century dimensions -- the circa 1864 building is the District's only remaining one-room schoolhouse -- help create a child-scale learning environment. The room's appointments do the rest: Those more than 36 inches tall need not bother looking for a place to sit. Cages housing a variety of furry, scaled and feathered tenants sit at floor-level around the perimeter of the room. At one end, a lop-eared rabbit snoozes in its hutch and turtles splash in an open-topped tank; at the other, a coiled snake glares through the glass of its aquarium.

A recent Friday morning finds the "To Bee" kids seated in a circle around a multicolored parachute. Underneath is a pile of objects that represent the division of labor between a hive's bees: a hard hat for the industrious worker bee, a pillow for the shiftless drone and, of course, a tiara for the queen. As the adults around the periphery lift the chute into the air, the kids are asked to run underneath one at a time and retrieve an object from the pile. Sometimes it even happens that way. More often, three run underneath at once, one takes off for the turtle tank, another scoops up the entire pile of objects, and yet another has to be bodily removed by his or her parent as the parachute descends. Naturally the game is a huge success.

So they do it again. Despite preschoolers' infinite distractibility, Hugh Squire, the museum's director of family programming, says they are his favorite age group to teach. "It's amazingly rewarding," he says. "They are so inquiring, so ready to learn -- everything is new."

The museum's educators hold brainstorming sessions to come up with class activities. "It's definitely a team effort," Fraser says. In terms of both content and presentation, she says, knowing your audience is key. Live animal encounters, for example, are perennial crowd-pleasers. (Except, of course, in the bee classes, where other critters serve as stand-ins for the main attraction.) Teachers make sure that no single activity lasts too long and that there's enough variety for a kid who hates one activity to have a good chance of enjoying the next.

"I don't expect any kid to come in and give me their attention for 15 straight minutes," Squire says. "I want to make sure it's not just kids sitting and listening to me talk."

Not much chance of that. The hour-long class passes in a black-and-yellow blur as the kids make antennae headbands from construction paper, pipe cleaners and pompoms; reassemble a large stuffed bee whose legs and antennae are attached with Velcro; and venture outside for a short bee hike. The Historic Schoolhouse is on the grounds of Battery Kemble Park, and once under its canopy of trees it's easy to forget that you're just yards from a city street.

Will your toddler come home and start throwing the word "thorax" around?

Probably not. Avery Gunther, who has taught Toddler Treehouse classes for three years, says their benefits are likely to be less concrete, like stoking a love of nature or helping a child overcome a fear of animals.

"They learn about behavior, rules and how to have fun," she says.

Other Discovery Creek offerings for the preschool set include Polliwog Pals, a pilot program for babies between six and 18 months old, and Babes in the Woods, a series of hikes for infants old enough to ride comfortably in a backpack carrier, but not too old to insist on getting out and walking themselves. The goal of these series is the same as that of Toddler Treehouse, Fraser says. "We want to introduce parents and children to the outdoors."

TODDLER TREEHOUSE -- Programs take place at the Historic Schoolhouse, 4954 MacArthur Blvd. NW. 202-337-5111. www.discoverycreek.org. Each session includes three one-hour classes. Cost is $65 per session.

Upcoming sessions:

Summer Senses -- June 5, 12 and 19 at 9; June 5, 12 and 19 at 11; or June 6, 13 and 20 at 9.

Itty Bitty Bugs -- July 10, 17 and 24 at 9; July 10, 17 and 24 at 11; or July 11, 18 and 25 at 9.

Animal Adventures -- Aug. 7, 14 and 21 at 9.

Hope Donovan, left, and Jack Sterling hang their beehives out in the woods outside Discovery Creek's Historic Schoolhouse location. At right, Oliver Snow places a bunny in the "B" Hive.