Little Annette Longenecker sat on her bay Dartmoor pony, Tiny Tot, chewing on a Tootsie Roll. She had just finished a clean round over the two-foot fences in the hedge ring.

The chocolate was her payoff. . .but not for the ring performance.

"She fell off out in the schooling ring," said Penny Longnecker, who had traveled from Mechanicsburg, Pa. with her daughter to the five-day Middleburg National Horse Show, which ended yesterday. "I promised her a candy bar if she didn't cry. It's the first time she's falled off jumping."

Annette, competing for the first time in long stirrups after graduation from the little-kid, lead-line classes, is a veteran of 3 1/2 years on a 20-show summer circuit.

Annette turned 6 on Sunday.

Ever the most casual traveler easing along Route 50 past shops and restaurants with names like the Iron Jockey, Dominion Saddlery, The Coach Stop and Red Fox Tavern catches the message: They take their riding seriously in Middleburg, Va. It is a tradition that stretches back to the turn of the 19th century when the area became known as the nation's horse and hunt capital and there's no strong indication that it is about to change soon.

Exhibitors of more than 700 ponies and horses from Virginia, Maryland, Pennsylvania, New Jersey and the Carolinas twisted along the ribbon of road that leads to the Foxcroft School where the show was held. Another stop on the circuit, another round of classes-all in a summer's work.

Jane Nichols, "the Perle Mesta of the Middleburg show," sat at her table under the yellow-and-white striped canopy that stretched between the two major rings. Heedless of the rain that on both Saturday and Tuesday sent a continuous drizzle over the awning edges, she wore her signature accessories, dark glasses, a sweeping brimmed straw hat and a small ransom in jewelry. Every day Nichols presided over a sideboard of solid, sensible fare she prepared for her friends and any newcomers who might wander into the reserved region of the show.

"Do come back on Monday," she enunciated last Saturday in tones that gave the generous invitation the ring of a royal command. "ThatS the day of the breeding classes and we always have quite a little party. Many of the old Virginia types will be here and the classes are just lovely with all those little babies and all. Breeding is terribly important to Virginia, you know."

Monday's balmy sunshine brought with it another problem in the form of yellow-ja3417.124ckets, which flew a kamikaze course through the tent, attacking the spare-rib main course and buzzing Nichols' guests. Some perfumy insect repellent just wasn't doing the job and reinforcements were found. A stable-strength bug bomb cleared the air and the party continued.

Horse shows come with a standard cast of characters, chasing a limited number of ribbons and as many points as they can gather on their way to the Washington International or the Garden. But the motivations are different. The pros do it because it's a living. Owners pay the pros to ride their horses because they want to own winners. The children and the amateur owner-riders are after the sport. . . and the glory. No one's in it for the money. . . even the professionals have to scrabble in order to support the high living on the circuit.

"It used to be just for the sport," said Jane Nichols, who doesn't show as much anymore. "There was no return and mostly trophies and ribbons. Now there are more professionals and it has gotten so expensive that they try to give purses. And in most shows the gate is for charity; that way those who ride can deduct their fees."

Old hands maintain that it's still the sport that counts. The contests at Middleburg are a more chummy test of skills than at some of the linger established A-class shows where it gets to be cut throat and big business.

Sure, the pros are around. Rodney Jenkins was there riding about 30 different horses for their owners, according to some estimates, but he is a Virginia boy who grew up on the circuit and He's accepted.

"There are more happy people here," said J. Arthur Reynolds, a resident of Warrenton whose grandson, wife and daughter were competing over the five days. "ThereS more of a possibility of winning ribbons. It's an even bunch of horses, well-matched, and you don't know before a class who will win a ribbon."

But later in the day, and through most of the show, Jenkins made a sweep of all the major events and left early to compete in a Long Island show that began yesterday.

Some things don't change. The competitors are mostly girls. And the girls bear a carefully chiseled similarity.

They are straight-backed and remote, within themselves, one might even say aloof. And they're 9 or 10, or 11, or reaching into the teens. The legs are long, teeth good. (A nonhorsey spectator asked quite seriously if they were bred this way. It's not an outrageous question.)

The hair is in braids, or skinned back under their tidy velvet caps, or trapped in nets that give the effect of a pageboy cast in concrete. And the faces. Looking at these poised, controlled young females whose determined jaws are firmly molded and whose face bones are clearly defined even to the delicate indentations from the cheek to the chin, one can easily imagine them in 40 years. They'll seem youthful in middle age; now they appear almost old.

Boys play no role in the feminine conversation when the mostly silent young riders do speak.

The talk is of horses, almost exclusively. And some of the standard buzz words heard wafting over the grounds are Jenkins and Melanie Smith (the '78 rider of the year and member of the U.S. Olympic team at the Pan Am games).

"Don't I wish I could be like her," said one pig-tailed adolescent, rolling her eyes to emphasize the enormity of the wish.

Riding is discipline and concentration and competition, and learning early on that life's not always fair. It's training in stoicism. Good form.

Kids grow up fast on the circuit.

Horse shows of any size come with an army of camp followers, the show gypsies and horse-supply merchants who tend to the needs of riders and horses. Some trail the circuit for months, traveling in large vans that are shops on wheels, reporting home to the parent store only at the end of the season.

At Middleburg, a rider could commission a portrait of his mount or his favorite dog. For $125, a mother could pick up a Pytchley riding jacket for her 6-year-old. ("The larger sizes cost about the same amount, too," the salesman at the Lees van from Hollywood, Fla., pointed out. "But you must realize that Pytchley makes the finest riding clothes in the business.") Vogel and Dehner make fine boots, too, for a couple of hundred dollars or so, depending on what you require. Hermes is into saddles; there are Gucci horse sheets.

The rainy weather didn't discourage attendance or dull appetities, observed Sue Swain, who was cooking hot dogs in one of the food trailers lined up near the entrance to the grounds. Swain is president of the Middleburg Volunteer Fire Department and Rescue Squad Ladies' Auxiliary which was providing the food for the second year.

"We bought based on what we bought last year and in the first two days we used up almost all of it," she said as she ladled some chili over a frank. "This has been a monster show as far as we are concerned."

Whole families were involved in the operation of feeding the crown of competitors and spectators who had come for the sporting event.

"It's been frantic," Swain continued. "My 10-year-old is over helping out with the drinks and my 15-year- old has been carrying ice. I started breakfast at 6:30 this movning and I'll probably be here until 8. It's a long day if you're here all day, and all these people are volunteering their time. All we get paid is what we eat. . .when we get the time to eat."

Renee Kidd, 15, from Harve De Grace, Md., was overseeing some last-minute grooming of her pony, one of three she was riding in the show. Slim and wiry, Renee wore on her arm the grosgrain ribbon that signified she was one of the top riders of the day, a star. There was the brief flash of a metal-brace smile and a pink flush of embarrassed teen giggles as she and a friend shared a joke. But then it was all business as she rattled off a series of orders to a coterie of younger, jeans-clad girls with all the precision and skill of a mini Marine sergeant.

Her informal complement of stable hands were delighted to do the most menial tasks and lobbied for more. Horse shows wouldn't work without the adolescent volunteers.

At horse shows, each rangy thoroughbred and compact pony appears to come with a support system of two or three humans and one dog. The canine population at these events has promted a motto among many show organizers. "We don't bring a horse to a dog show; don't bring your dog to a horse show." But like the leash laws these officials try to enforce, it is shrugged off. What's more, the officials even set up competition for the dogs.

There were great Danes and German shepherds, poodles and old English sheep dogs and a bumper crop of corgis. The breed in greatest supply at Middleburg was the Jack Russell. Unrecognized by the AKC and not often seen elsewhere, these tiny black and brown and white terriers, bred to chase foxes into their dens when they go to ground and send them out to the pack of larger hounds, are a passion among the horsey set.

Annie Dunning, 10, from Boyce, Va., was carrying her Jack Russell, Gingersnap, through the concession tents.

"We got her this really nice collar, but now we can't find it, and I bought Head and Shoulders shampoo for her but got used on the pony's tail," Annie said.

"Last year," she added, "Gingy was a disgrace. She sat down when she came out of the box and didn't even run over the jumps. She's a victim of her own glory-she's awfully stuck on herself. But this year we might win in the tack room guard dog contest because my father has taught her this trick to growl and seem ferocious when you hold your hand up in just a certain way. Our little cart for the costume class bumped too much along the ground so we couldn't use it and I don't think we'll be in the trick class. . . but maybe there's a chance in the others. . ."

What Annie was talking about were the classes scheduled at the end of the day. After the horses were finished, the dogs competed for rawhide bones and ribbon and their bit of glory (cocktails were provided for the exhibitors).

At horse shows, there aren't many free rides. Even the dogs have to perform.

And sometimes the early morning flush of success can turn into an afternoon's defeat.

Rose Marie Bogley, who won the Tuesday morning sidesaddle class, said, "I think I deserve two blue ribbons for getting up so early." Artist Wally Nall added: "The only thing that gets her up early is a pack of foxhounds."

But Bogley's good fortune ran out later in the day when she placed dead last in the second sidesaddle event. Competition, as she observed, "keeps you humble."