Vitas Gerulaitis, the lion's-maned party boy who drives his Rolls-Royce to New York's discos, lost today at Wimbledon to a balding fugitive from a janitor's mop and pail.

And 17-year-old Mats Wilander, anointed by the British press as "the new Swedish heartthrob," lost to a hawk-faced bomber who couldn't walk nine months ago.

Mark Edmondson beat the third-seeded Gerulaitis, 7-6, 4-6, 6-4, 6-3, in a quarterfinal match. Brian Teacher ruined the teeny-boppers' day by dropping his explosive serve on Wilander often enough for a 6-4, 6-4, 6-3 fourth-round victory.

Now Edmondson goes into the semifinals of this dreary men's tournament against second-seeded Jimmy Connors, who humiliated the Australian with the loss of only three games in the final at Queens last week and now is swelling with confidence as he points toward a Sunday final against John McEnroe, the defending champion.

Connors is so sharp that the sixth-seeded Gene Mayer, today's 6-1, 6-2, 7-6 victim, said, "It took 3 1/2 minutes."

For a second straight year, unseeded Tim Mayotte, the 1981 NCAA champion from Springfield, Mass., made it to the quarterfinals. His straight-set conquest of Britain's Buster Mottram puts Mayotte against Teacher on Friday, with the winner meeting Friday's survivor of the John McEnroe-Johan Kriek quarterfinal.

That semifinal will be Saturday, as, most probably, will be the Connors-Edmondson match. The return of rain today after two sunny days put the schedule off again. But it is certain the women's semifinals will go on Friday: Billie Jean King against Chris Evert Lloyd, and Martina Navratilova against Bettina Bunge, who today beat Anne Smith, 6-3, 2-6, 6-0.

Though Edmondson is 12th-seeded here, Gerulaitis was a solid favorite because his greater athletic skills had been complemented the last 10 days by new-found power in his first serve. Always good on grass, Gerulaitis reckoned he had a shot at winning the tournament he likes to put down as "too arrogant" for its own good.

"It's worth millions to win," he said the day before he went on Court 2, a notorious site for upsets because of its uneven surface, and lost to the scowling Edmondson, an Australian who during his previous victory unsuccessfully demanded the removal of the Union Jack from a flagpole at courtside. The fluttering flag cast a shadow on the court.

No flag flew near Court 2 today, but the bumpy court itself and a misting rain that dampened the ex-janitor's shining pate caused him no end of complaint later. The court was a "disgrace," he said, adding that for three games in the rain he could barely stand on the slick grass.

As it happened, Gerulaitis' serve was at its best in that early going. Not only that, the New Yorker also broke Edmondson's powerful serve three times to win the second set.

"I said to myself, 'Eventually, he'll have to miss a few first serves," said Edmondson, who turned 28 this week but could pass for 38. He won the Australian Open in 1976, the year he moonlighted as a janitor to make beer money. He is heavy in the thighs and heavier behind him, the kind of man for whom gentleman's jeans were invented. Yet when Gerulaitis did miss first serves, Edmondson was quick enough to devour the seconds.

"And in the second set, he made quite a few easy errors," Edmondson said for Gerulaitis, who refused to attend a press conference. "Against his second serves, I was able to whack away at my volleys."

As for the Connors semifinal and a possible go at McEnroe, Edmondson, who has lost only two sets in five victories, said, "Jimmy beat the hell out of me at Queens. I've never beaten either of the two. But then, I hadn't ever beaten Vitas."

Also an Australian Open champion (in 1980, when he was ranked 12th in the world), Teacher gave a classic demonstration of the grass-court game to Wilander, who in his tennis infancy is a clay-court specialist.

In November, Teacher tore ligaments in his left ankle and couldn't play competitively until April, when he rejoined the tour in Brussels. Now with his movement good again--he wears high-top basketball-like shoes to firm up his ankle--Teacher is the overpowering serve-and-volley player that Wilander figured would put him out of the tournament.

"I'm not disappointed, because I didn't count on doing too much," said Wilander, who as an unseeded player won the French Open on clay two weeks before coming here.

"Mats was winning games with three or four first serves in every time," said Teacher, 27, who is 6-foot-3 and very thin. "I knew I'd get a chance to come in when he missed the first serves. Then I'd break him."

Exactly.

So weak were Wilander's defensive stabs at Teacher's crackling volleys that on three occasions the lanky Californian smashed overheads so violently they bounced out of the playing area and into the bleachers.

Meanwhile, Teacher, who begins his serving motion by first slowly dipping his racket head in the opponent's direction as if waving a curse onto him, fired his steeply-angled serve with such velocity Wilander could only react in self-defense.

His returns blooped back across the net, there to be smashed hither and yon by the shambling figure of Teacher. One return was so pitiful, so slow to come to earth, that Teacher eventually hit it sidearm, sending it five rows into the bleachers at side court.

"I feel like I can play with the top players again," Teacher said.