It's 12:15 p.m. on the panda watch. Ling-Ling, America's cuddly, black and white giant panda, is stretched out on the floor of her den at the National Zoo -- all 6 feet, 260 pounds of her -- sound asleep. Three video cameras above monitor her every movement. Styrofoam panels block the public's view. Blue lights simulate a moonlit night.

Ling-Ling, the object of all this attention, may be pregnant. But then again, she may not be. No one really knows.

She was artificially inseminated on May 17 and 18, and could have her cub -- if she's pregnant -- in the third week of September. "By the middle of October," says Dr. Robert Hoage, panda expert, "if she hasn't shown any pre-partum behavior or given birth, we will have to start seriously considering that she's not pregnant. At this point, we really don't know."

Hsing-Hsing (the possible father) paces back and forth in his den, scowling at the tourists, who are flashing their cameras at him.

Lingg at the tourists, who are flashing their cameras at him.

Ling-Ling (the possible expectant mother) rolls over, looks at the camera and goes back to sleep.

Is she or isn't she?

Francis (Buddy) Dreher, zookeeper, in the panda kitchen next to the video monitor, preparing the rice-based gruel that supplements her bamboo and fruit diet: "I hope she's pregnant, but I don't see any change in her movement."

Tommy McClinton, tourist from Baltimore, watching Ling-Ling on the remote monitor set up in the lobby of the zoo's education building: "Who the hell knows. I'm just glad I got here to see them before they close the panda house next week."

The watch continues. 12:35. Ling-Ling sits up in a resting posture, her legs stretched out on the floor, her head hung on her chest. She scratches her chin.

Last weekend, FONZies (Friends of the National Zoo) begin a "possible pregnant watch," pulling three-hour shifts all night long, looking, Hoage says, "for actions not characteristic of her normal tine, any high-intensity activities, or nesting behavior (small bits of straw have been placed in her den in case she's inclined to build a nest.)

"But so little is known," continues the 34-year-old primatologist, "we're not absolutely positive what the indicative behaviors are. The fetus is only four ounces at birth and pandas don't show any signs of pregnancy. That's why we're doing this watch."

Since Ling-Ling was artificially inseminated in May, Hoage and his colleagues have been recording the giant panda's every urination, leg cock and handstand, hoping for signs of success. Until recently, only the Chinese were known to have artificially inseminated giant pandas with success -- they have a two - for - five record so far. Last month, however, a cub was born to Ying-Ying at the Chapultepec Zoo in Mexico City, but it died on its ninth day when its mother sat on it.

12:37. Ling-Ling gets up on all fours and pads off to the corner of her den. She grabs a six-foot bamboo in her left paw and begins munching. At home, in her native Szechuan, China, she prefers "fountain" or umbrella" bamboo. Here, she eats a nameless brand, grown in the District.

Ling-Ling, 11, was artificially inseminated, Hoage says, because after several years of abortive breeding atempts, zoo officials decided that 9-year-old Hsing-Hsing was showing a hopelessly "ineffective mating posture. He can't do it. We don't know why."

Then technically, Ling-Ling is a virgin?

"It's irrelevant," says Hoage. "Let's just say that technically, he's not been an effective mat, ergo . . ." he shrugs his shoulders.

The scientific community, Hoage says, doesn't really know a whole lot about pandas. There are only about 50 in captivity in the world, and no one knows exactly how many are loose in the wild. This week, the zoo's chief veterinarian, Mitchell Bush, went to Mexico City to find out what he can from panda experts down there. Next year, an expedition to China is planned. fAbove that, he says, "we're on the forefront dealing with a relatively new phenomenon. We're learning as we go along."

You would think that the Chinese, when they presented the pair of rare mammals to former President Richard Nixon during his good will trip to the mainland in 1972, would have included instructions.

"Well," says Hoage, "they did recommend that we keep them separate, but close enough to exchange looks and gestures."

12:45. Ling-Ling puts down her stalk, walks to a rock and rubs her hind-end against it. She sits down again, watching a mouse run across her den.

"Some people," Hoage says, "have taken issue with artificial insemination, saying it's against her will. We feel we are helping to preserve the species . . . . Breading is the wave of the future in zoos. Countries are not letting animals out anymore. Zoos are beginning to become animal producers rather than animal consumers. They breed and then sell their surplus."

1:03. Ling-Ling stands up, then falls to all fours, walking back toward a corner. She beaches herself on the concrete and goes to sleep.

"Since the birth in Mexico City," Hoage says, "this birth has been built up like cheerleaders. If she does have a baby, it'll be, well, pandamonium."