A REPLICA of a limestone sinkhole spattered by a 40-foot waterfall in a Central American jungle is blurring the line between zoo and museum.
The site is the Cockrell Butterfly Center, part of the Houston Museum of Natural Science. As the name suggests, thousands of butterflies swarm in the Cockrell's tropical vegetation.
And so do thousands of delighted visitors. True, the museum also boasts the Brown Hall of Entomology, an eye-popping if conventional exhibit of mounted specimens in glass cases. But what draws the crowds is the cenote (``sacred well,'' in Spanish) or sinkhole, where a visitor may discover a flying jewel on his sleeve, fanning its wings.
It happened last week to young Kathleen Barkley. ``She was delighted,'' says Clara Collins, a neighbor who brought Kathleen and her own three children. ``She screamed and it flew away.''
James, Mrs. Collins's sixth-grade son, preferred viewing the Cockrell's live selections to the butterfly specimen that came with his home microscope kit. At the museum, ``it was hard to find two that looked alike, there were so many,'' he says.
The Cockrell, which opened in July, is one of a half dozen such facilities around the United States. Though Europeans have browsed through butterfly gardens for three decades, this country's first one opened just 10 years ago in Ft. Lauderdale, Fla. Others will be completed in Denver and New Orleans this year, and St Louis is also planning one.
``It seems to be the hot new item,'' says Nancy Greig, the Cockrell's director.
Ironically, the Cockrell came about because the museum acquired a 100,000-insect collection in 1987. Lacking display space, the museum trustees began to plan an addition. Then, hearing about butterfly gardens, they visited one at Calloway Gardens in Georgia.
``We were impressed with the numbers of people they were getting,'' says museum president Truett Latimer. ``It was a crowd-pleaser.'' The trustees liked the idea of an exhibit that presented live as well as preserved specimens, a groundbreaking concept for a museum.
The Cockrell was included in what grew to be a $20 million expansion. The butterfly center is enclosed by a cone-shaped greenhouse, 70 feet tall and 105 feet in diameter. Its 600 panes of glass - each custom-cut because none is rectangular - face the southwest for maximum sunlight. The temperature inside ranges from 78 to 85 degrees F. with 80 percent humidity.
``If it weren't so hot, it would be real tranquil,'' Mrs. Collins says.
``It seems ridiculous to attempt to recreate what is already outside,'' Mr. Latimer says with a laugh. But Houston's weather is not always a steamy enough tropical habitat.
All the plants come from Western Hemisphere rain forests. ``We're trying to be authentic,'' Dr. Greig says. The chosen species must be either good nectar sources or valuable rain forest plants, such as the coffee bush, papaya tree, and guava tree.
The butterflies, representing more than a hundred species, come from Asia as well as North and South America. The staff debates the authenticity question, but Greig figures that the public won't care where a beautiful butterfly came from.
It's also a matter of economics. Butterfly life spans are as short as a few weeks, so the Cockrell must import 4,000 a month in the chrysalis stage. Butterfly ``farms'' in Asia charge $1 each. Latin American farms charge $2.50 or more.
On the other hand, the many dollars earned by Latin American farms probably prevent rain forest from being burned for cattle ranching, Greig says.
``We haven't found a butterfly farm in Africa yet, although I just got a call from a woman in Kenya,'' Greig adds. She expects to receive samples in a few weeks.
Why doesn't the Cockrell simply breed the butterflies it buys?
``We're not supposed to,'' Greig says. The US Department of Agriculture is concerned about the risk nonnative butterflies might pose to crops in the caterpillar stage. The museum also is forbidden from importing any citrus-eating butterfly.
In fact, the butterflies do mate. But they will lay eggs only on certain plants, and those are not present in the Cockrell. So the fertilized females die without laying eggs. Native butterflies are allowed to breed.
There's more to operating the Cockrell than just figuring out how to keep the butterflies from being sucked into the return air vent of the climate system, Greig says.
Since not all butterflies visit flowers, the Cockrell also has feeding stations where the insects might smell ``a nice fragrant rotting banana,'' Greig says. Supplemental nectar is provided in a red sponge on a yellow plate.
Controlling unwanted bugs is a challenge, since pesticides can't be used. ``We have a bad ant problem,'' Greig notes. Ants like to eat the excretions from aphids, and will herd them like cows and protect them from the parasitic wasps that the Cockrell's staff has introduced to eat them.
More than half a million visitors are expected at the Cockrell this year. ``For the price [$3 adults, $2 children], I thought it was really a good bargain,'' Collins says.