Invitations for The Hunt Ball, Wolf Trap's celebration of its "twelfth successful season," went out this week. They are heavy blue-and-white embossed cards tucked inside little envelopes with enough tissue paper lining to handle a mild cold. In the bottom left-hand corner is the dress instruction: "Black Tie, Scarlet if convenient."

Scarlet? Does that mean a red cummerbund, women in red dresses, maroon dinner jackets, or, as one local secretary queried, "Are you supposed to come with a scarlet letter on your chest?"

"If they don't know what it means, then it obviously doesn't apply to them," answered Austin Kiplinger, president of the Kiplinger Washington Editors Inc. and a member of the Potomac Hunt club. "It's like the Louis Armstrong story. A woman once asked Louis to explain jazz and he told her: 'If you got to ask, you ain't gonna get to know.' "

But a lot of people are asking. Asking newspapers, formal-wear shops and Wolf Trap itself.

"We've had a dozen or more calls this week about 'scarlet,' " said Dan Frederick, manager of M. Stein & Co., a formal-wear outlet. "It completely caught us off guard."

"One man called here and said he went to a formal-wear shop and wanted to rent a scarlet tux," said a spokeswoman from Wolf Trap Farm Park. "They had no idea what he was talking about."

"A lady called just yesterday and asked what 'scarlet, if convenient meant,' " said Paul Glass of Royal Formal and Bridal shop. "I had no idea what she was talking about and I've been in the business a while. We don't rent anything like that, but I could probably order it."

You can't order it, though. Not the real thing at least.

"Scarlet" is the evening wear equivalent of a man's "pinks," the red riding jacket worn by a fox hunter who has been awarded his colors. "It's a very prestigious type of thing. It means a man has proved himself to be a good member of the hunt," explained Rose Marie Bogley, a member of the Wolf Trap ball's executive committee and a proven hunter in her own right. "The minute a man receives an invitation to a hunt ball he immediately goes and has tails made up in scarlet."

"Scarlet is the evening dress that goes along with formal hunt attire. It's really just a scarlet tail coat," said Kiplinger. "It's the same as white tie but with a scarlet coat."

Okay. A pink is a scarlet which is really just a red tail coat. It's only worn by a hunter who's been awarded his colors by the master hunter. But what about women? What about a woman master hunter?

"For the hunt she wears her club colors on her collar," explained Bogley. "At night, to be absolutely correct, a woman is supposed to wear black or white to a hunt ball. But nobody really does that anymore. Except me, that is."