Dr. Dale Marcellini thinks he knows why the Reptile and Amphibian House ranks second in popularity only to the panda pad at the zoo.

"People either love them or think they're awful," says Marcellini, who's curator of the creepy-crawlies. "And do people like awful things? Of course! That's why they go to horror movies -- to be titillated."

Now, in a recently opened room in the Reptile House, people can be titillated up close -- and learn about reptilian creatures in the process. Herplab, short for herpetology laboratory, features recordings of frog calls, films of lizard fights, tortoise skeletons to piece together -- even a live snake-of-the- day and frog-of-the-day you can check out and get to know.

As soon as one of these critters is checked out and taken in its own plastic box to one of the tables, the human question-asking reflex is activated.

"Why is it sticking out its tongue?" asks a visitor staring at a corn snake in a box with a mirror on the bottom that reflects the snake's corn-kernel-like underbelly.

The answer (the snake is not sticking its tongue out at you -- it's using its tongue to taste and smell the air) is right there in the same box, separated from the snake by a partition. Visitors' questions are anticipated even before they're asked, thanks to a team of experts who spent about three years setting up Herplab under a grant from the National Science Foundation.

"We sat down with families and found out what they wanted to know," says Judith White, the zoo's education chief. "Then we talked about what we thought was important. We tried out prototypes of the boxes on visitors to the zoo in June, then revised them. What we're doing is developing materials to help families learn biological principles, using reptiles as tools. Most reptiles are small, so they're easier to handle than mammals and it's easier to look at many different species."

Perhaps White is partial to reptiles because she's married to Marcellini, whom she met when, as new employees, they were being fingerprinted. The couple does not, however, keep any creepy-crawlies at home.

"Snakes in your house are like plants, not pets," says Marcellini. "As pets they're terribly boring. I used to have lizards. Lizards are somewhat social, more complicated. They're the intellectuals of the reptile world."

Lizards' social -- some might say anti- social -- activity has inspired a movie at the zoo. Informally dubbed "Bonzo Meets Godzilla," the film illustrates the fact that lizards, like lions and bears, are territorial.

Filmed on location at Herplab, the short flick opens with a shot of a kingfish lizard -- a male, of course -- resting on a rock on its own turf when a young upstart comes along. The challenger flaps his dewlap (a reddish bag of skin between the jaws) -- in lizard terms, this is like waving a red flag. The challenge is met by the incumbent's dewlap, and the battle is joined. To find out which of the leaping lizards wins the turf, you'll have to see the movie -- and play the territoriality board game and read the co-ordinating comic book. They're all free, at Herplab. SNAKE MEET Herplab is open from Wednesday through Sunday, noon to three in the Reptile House at the National Zoo. Only 20 people are allowed in at a time and children must be accompanied by an adult.