IF YOU THINK reptiles are some of nature's most beautiful and fascinating creatures, this is the show to see. If you think that reptiles are creepy, scary or just plain unappealing, this is still the show to see.

Just ask the keyed-up kids at Rockville's Luxmanor Elementary School who are about to get their first look at Reptile World. The moment the students file into the all-purpose room, every eye zooms to the large padlocked crates on stage. Everyone expects a circus- style start, with crates flying open and animals jumping out. But what they get is much better -- a low-key, information-packed program by Michael Shwedick, a soft-spoken guy who wants kids to see the beauty and fascination of his creatures.

Shwedick, who appears at schools throughout the area and will be presenting a Reptile World program Saturday at the Barns of Wolf Trap, offers a show that beguiles as it educates.

He begins by calming the nervous excitement reptiles often evoke. Not a single scale, nail or tail appears until Shwedick has everyone attentive, but not tense. Then comes this delightful introduction: "My turtle's parents are green, and her grandparents are green, and all her cousins and 49 sisters and brothers are green, but Buttercup was born a very rare, soft-shelled albino Siamese turtle from Bangkok, Thailand."

To gasps of pleasure, Shwedick brings out a lovely, large white turtle with a lemon-yellow shell and pink eyes.

While Buttercup "swims" gently atop Shwedick's palm, he goes into the kind of detailed description that helps make his reptile presentation so fascinating. Among other things, Shwedick gives Buttercup's history and tells how large she'll grow, how long she'll live, what she eats, and why an albino turtle could never live in the wild without camouflage.

"I have seen an albino giraffe," he says, "and yesterday I met two third graders who were albinos. They were very special and beautiful, just like Buttercup."

Next on stage is Iggy, a show-stopper if ever there was one. This stunning, five-foot- long South American iguana is pale green with an orange overlay; there are large black bands on his tail, and spines run the length of his back. The spines look dangerous to a predator but are really paper thin. Shwedick tells the enthralled crowd that if a jungle cat pounced on Iggy's tail, the tail would come off and wiggle for 20 minutes, confusing the cat while the reptile climbed to safety. (Yes, it would eventually grow back, too.) While Iggy loves American cheese, he's fussy about taking vitamins unless they're mixed in fruit cocktail. Iggy gets to sit on a branch for the rest of the show, occasionally upstaging everyone simply by bobbing his head or licking his lips.

Cookie was the size of a hot dog when Shwedick met her, bu now, four years later, this American crocodile is quite an armful at four feet, nine inches and 39 pounds. Shwedick explains that 18 of the 19 crocodile species are endangered, and he talks about poachers and captive breeding programs. He does not gloss over the fact that crocodiles sometimes eat humans, but calms any fears by stressing that all reptiles instinctively run away from people unless scared or driven by hunger. When Cookie cooperates (which doesn't happen in every program), by staying calm as she is hoisted upright, Shwedick remarks that "she is allowing me to share her underside with you." He sums up by saying of Cookie and her kind, "She will never be my pet. She doesn't like me but she doesn't dislike me. Their real concern is survival."

Even as the kids marvel at the animals, they sit wide-eyed in wonder at Shwedick's ease in handling the ungainly reptiles while keeping up his flowing, easy-going talk. Such professionalism began in the 10th grade, when a kind-hearted biology teacher allowed Shwedick to keep his pet snakes at school. (His mother couldn't even look at a picture of a snake, much less endure the real thing in her home.) Shwedick started giving talks about his pets to other students, and from there, he and his brother Bruce went on to form their own company, Reptile World. Today they own 147 reptiles and give educational programs for pre-school to college-age students. Though Shwedick is fascinated by all reptiles, his favorites, he acknowledges, are still the snakes.

They're the kids' favorites, too, which is obvious from the burst of applause that greets their appearance on stage at Luxmanor.

First comes Oliver Twist, a boa constrictor, of course, followed by Junior Miss, an Indian Rock python. Shwedick hoists the boa onto his shoulders, saying, as he does at many points in the program, "I am not doing this to show off, because you know that that's not what my animals are for." While he continues talking and walking around the stage, Oliver Twist gradually drops to his waist and does what boa constrictors do. As he coils around him, the crowd becomes noticeably nervous, and Shwedick stops his talk to reassure them that "Oliver Twist isn't squeezing me, because he knows he cannot eat me and he isn't panicked."

Junior Miss, twice Oliver Twist's seven feet, is 175 pounds. It takes three strong men to lift her, and it's hard to believe she hatched from the small, leathery egg that Shwedick holds up. The diets of the large snakes are no small part of their fascination, and Shwedick tells it like it is. Somehow, with that gentle and humorous style of his, even the eating habits of these animals seem absorbing rather than abhorrent.

At the end of the program, all the kids are invited to pet the python's elegant, patterned skin. They do, every one of them, with absolutely no squealing or face-making or silliness. It's clear they feel the calm and the wonder that Shwedick has imparted.

REPTILE WORLD SHOW -- Reptile World programs will be presented Saturday at 11 a.m. and 1 p.m. at the Barns of Wolf Trap. Tickets are $4 each and can be reserved by calling 938-2404. For more information, call 255-1939.

Reptile World, which is based in Largo, Md., also does programs in private homes and allows its animals to be photographed for educational purposes. The phone number is 301/464-5600.

Mimsi Kromer Milton last wrote for Weekend on touring and raspberry picking in Virginia's Westmoreland County.