Species: Morpho peleides

Habitat: Tropical forests

Range: Mexico to Colombia and Venezuela

''Literature and butterflies are the two sweetest passions known to man,'' Vladimir Nabokov, the novelist and lepidopterist, once wrote.

There are 20,000 species of butterfly, and one of the most dramatic is the morpho peleides, large and cobalt blue, which lives in Central and South America and is particularly plentiful in Costa Rica.

Dwelling in a canopy of rain forests, the saucer-size morphos (with a five- to six-inch wingspan) sparkle like blue gems. Their iridescent wings are the result of a microstructure on their upper surface that refracts light, causing them to shimmer as the butterflies bask in the sun.

''In all of the Neotropics there are few sights more spectacular than watching the flight of a male morpho lazily sail above the canopy of the rain forest or along a river on a brilliantly sunny day,'' wrote Philip J. DeVries in ''The Butterflies of Costa Rica and Their Natural History.''

Morphos start life as an egg laid on the leaf of one of a select few rain-forest plants. The egg hatches into a larva, which in the case of morpho peleides is a bright red-and-yellow caterpillar with a triangular head capsule covered with stiff hairs. The larva forms into a pale green egg-shape pupa. Then the eternally magical process of metamorphosis transforms the green blob into the magnificent morpho, which has a fleeting life of just three or four weeks.

Morphos use their long, strawlike proboscis to feed on the juices of rotting rain-forest fruits. When feeding and sleeping they close up their wings, hiding the brilliant blue outer surface. The under surface is mottled brown with several eyespots that provide camouflage.

As morphos fly, the different colors of the upper and underside of their wings create a visual illusion that can confuse birds and other predators. The morphos seem to bounce along in the air, exhibiting flashes of blue as they flap their bicolored wings. But, according to Mr. DeVries, the slow, floppy wing beats can immediately accelerate into a wild, swooping flight when danger is near. LYNNE CHRISTENSEN

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