The National Zoo celebrated its 100th birthday last week with Barbara Bush leading the noisy hoopla, but over at the Smithsonian's Insect Zoo, things were so quiet you could actually hear the giant Madagascar hissing cockroach hiss.

The silence was broken by shrieks and gasps from a class of first-graders who gathered round to watch Cleo, the orange-kneed Mexican tarantula, gobble her weekly meal of a live cricket.If you blinked, you'd miss the show. Might these spiders be desperately hungry on such a spartan diet?

"Tarantulas don't burn a lot of calories," said Sally Love, the Insect Zoo's director. "They just sit around, waiting for something to bump into them. They can go for a year and a half without eating anything at all."

Love is plainly in love with bugs.

A George Washington University graduate with a degree in biology, she postponed plans to get a master's degree and quit her job as a "grunt" on Capitol Hill seven years ago to run the tiny Insect Zoo at the end of a third-floor hallway in the National Museum of Natural History.

"Insects are gaining momentum in popularity for some reason," said Love, who has appeared on the Johnny Carson and David Letterman television shows as well as West German and Canadian TV to display the biggest, showiest specimens from her zoo.

"Everybody has a horror and a fascination with insects," she said. "But when people try to take a close look at insects, they say `hmmm, they're not so bad after all.' In fact, they are really very interesting."

Among the dramatic bugs she has chosen for her TV appearances - she calls them the "Oh, my's" because of the audience reaction - are some of the zoo's 50 or so tarantulas, a whip scorpion from Arizona, the Giant Walking Stick from New Guinea, 3-inch cockroaches, rare leaf insects from Sri Lanka (whose disguise is to look like the leaves they are devouring) and scarab beetles and and cone-headed katydids from Peru.

To the delight of schoolchildren on field trips to the zoo, Love consents to stare cross-eyed as a giant Madagascar hissing cockroach crawls up the side of her nose.

"For this I went to school?" she says with a giggle.

Love receives $20 a week to spend on fresh fruits and vegetables for her bugs. Most eat things like romaine lettuce and bananas, but the large milkweed bug prefers sunflower seeds and raw peanuts.

The meat eaters - tarantulas, scorpions, centipedes and the like - eat crickets, with an occasional caterpillar or beetle larvae tossed in for a treat. The tobacco hornworms, of course, like tobacco. And the giant coconut crabs from the Seychelles in the Indian Ocean can't get enough of coconut cake, with vitamin-rich fish food sprinkled on top.