Sen. Joe Biden (D-Del.) is wiping watermelon-pink lipstick from his lower lip. He's reaching a hand around the Maryland-Delaware Watermelon Queen's rib cage, mugging for yet another photo.

"Sure! Do it again!" Biden cheers on the photographer.

"This is hard work!" he says with a hardy har-har-har. He resumes chatting with Angie Riggin, the 19-year-old melon queen. She has teased blond hair, rind-green eyes. She's wearing a sleeveless, plunging V-neck dress, with two watermelon-shaped appliques on her hips.

Surrounded by plump, ripe melons and wedges of sticky, wet pulp, Biden is having a fine time at the seventh-annual Watermelon Feast on Capitol Hill. So are the Hill pages (all guys). So are the Hill interns (mostly guys). So are the various watermelon-state congressmen with sugary water dribbling down their chins.

Agriculture Secretary Edward Madigan proclaimed yesterday Watermelon Feast Day. A day for gorging on juicy pink fruit. Spitting slippery black seeds. Gawking at the National Watermelon Queen from South Carolina and her court of eight state watermelon queens.

"We're picking up on watermelon babes," says Sanford Michelman, 21, a Senate intern.

His sticky-fingered friends are passing around signed glossies of the beauties. Michelman's favorite is the national queen, Pam Mizzell: a cheerful bouquet of blond curls, heavy makeup, a diamond tiara and a low-cut red and white dress.

"I like her because she's intelligent," Michelman says. His buddies guffaw.

The event certainly is generating interest in melons.

"We have a fancy thing in the Senate called the filibuster," Biden continues, still chatting up the Maryland-Delaware queen. "That means the senators talk a lot."

Biden tells the queen how desperate he is to get votes on his crime bill. "And the CFE {Conventional Forces in Europe} Treaty, I'm in charge of that too," he adds.

Here comes Bruce Price, president of the National Watermelon Association, the event's sponsor. "Hello, Mr. President!" Biden says.

A startled Price: "I'm not used to being addressed as 'president.' "

"Nor am I. But it sounds good!" exclaims Biden, whose presidential ambitions are thought to be ripening for 1996.

How high spirits are soaring this noon over the grassy courtyard of the Russell Senate Office Building!

Sen. Jesse Helms (R-N.C.) is hugging the North Carolina queen. He's wearing a pink and green North Carolina Watermelon Association hat for the occasion. Someone yanks off the hat for a picture.

"Hey! I don't have any hair!" Helms objects as the camera clicks.

Suddenly his maw is buried in a loaf-size piece of watermelon.

"Now you have a bite." Helms offers a slice to the North Carolina queen.

The senator says he came to the fruit fest because the queen invited him.

"When someone looks like that from North Carolina, you listen to her," says Helms, grinning.

But his queen is gone. Off to the seed-spitting competition.

Three spits to a queen.

Miss Indiana steps up to the white line first. She extends a high-heeled foot. Arches her back. Throws back her mane. Grabs hold of her crown. Screws up her mouth. Purses red lips. And shfooooo ... the aerodynamic little pellet shoots straighter than Robin Hood's arrow.

"Ahh-yahh," gasp the awed spectators.

Not to be outdone, the Maryland-Delaware queen fires a black wet bullet 22 feet 7 1/2 inches. (The record is 66 feet 11 inches, set in Illinois.) She blows away the competition.

"Boy can she spit seed!" marvels an intern.

Would any of the congressmen like to face-off with the ladies?

Dick Nichols from Kansas volunteers. He is slightly disoriented. Holding a messy wedge in one hand.

"Step up to the line and spit your seed!" commands the national queen.

"Do you have some in your mouth?" Nichols asks the Maryland-Delaware queen.

She lets one rip. It's out of the park. The crowd goes wild.

Nichols blows.

"Is it raining, or is it him?" Phil Bellaria, a Hill intern, wonders out loud.

Nichols defeats the queen and bursts into excited paean: "We love watermelons! We love ag people! And we particularly love these queens!"

Nichols carries off his prize, a whole watermelon. The crowd disperses. Half-devoured pink slices are left behind.