It all started with the octopus.

When she died of old age in February, her tank at the National Zoo’s invertebrate exhibit was left empty. The zoo’s administration never started looking for another creature to take her place. And the keepers wondered.

Meanwhile, the 1930s building that the spineless animals were housed in was falling apart. There was peeling wallpaper, leaking pipes, cracked tanks — and a $5 million estimation of what it would take to fix it all. So the keepers worried.

Then, on June 16, the announcement was made. Within the week, the invertebrate exhibit would close for good. Now the keepers knew.

“I thought maybe we were in the clear financially, but we know now that’s not the case,” said curator Alan Peters. He helped create the exhibit in 1987, when the idea of having an area for invertebrates only was unheard of across the country. The dark and damp space housed a wide variety of animals with one commonality: no spines.

Ella Stough, 9, meets a butterfly at the National Zoo’s invertebrate exhibit, one day before the exhibit was scheduled to close. (Yue Wu/The Washington Post)

Despite the gloominess and drizzle of Saturday’s weather, thousands of people streamed through the zoo, past the lions — visitors remarking, “Don’t you just want to cuddle with him!” — the playful otters — “This just never gets old” — and the iconic panda — “Follow daddy’s finger, he’s up in the tree!” — to stand in line for what was billed as the final chance to see the bugs, jellyfish and the empty octopus tank.

“They might look disgusting, they might feel weird, but they make a huge difference in the lives of all of us. They allow the flowers to grow, the birds to eat, and they are a great teaching tool about how life works,” said Enrique Ograj, who brought his 11- and 14-year-old children to the exhibit for the last time, partially to try to curb his daughter’s fear of squids.

That fear of squids, or tarantulas, or beetles — or any of the other invertebrates that might not be at the top of anyone’s favorite zoo creature list — is one of the main reasons invertebrate conservationists are upset about the closure of the exhibit.

“This pushes invertebrates out of the limelight even more,” said Matthew Shepherd of the Xerces Society, an invertebrate conservation organization. “When people don’t get to see and learn about invertebrates, then they only think of them when they see honeybee swarms or bedbugs or cockroach infestations on the news.”

Curator Peters and his zookeepers have been trying to bridge that divide for 27 years, bringing zoo visitors up close and personal with peacock mantis shrimp, goliath bird-eating tarantulas and hissing cockroaches.

In the final hours of the exhibit’s existence, children pressed their noses against the tanks of the coral, asked volunteers how leafcutter ants build their homes and jumped back when they realized there was no glass separating them from the webs of the golden orb spiders. It seemed, one volunteer said, like any other day.

Meanwhile, the staff was celebrating and mourning, toasting with plastic glasses of champagne and passing around scoops of chocolate and vanilla ice cream. Peters’s daughter picked out the flavors.

Sitting in a moist-smelling back room, the ice cream melted as the keepers and volunteers waited for Peters to finish interviews for the many news cameras that arrived at the zoo Saturday. When bug fans on local and national media, Facebook and blogs spurred a wave of public outcry about the closure, the invertebrate exhibit garnered more attention than it had experienced in years, possibly in its existence.

A change.org petition to keep the exhibit open had more than 3,000 signatures by Monday morning.

Terri Jacobsen, the Bethesda, Md., resident who created the petition, stood behind the news cameras Saturday, waiting for her chance to have a word with Peters. Jacobsen pointed out that without giving the community time to respond, there is no way for money to be raised to save or improve the exhibit, as has happened in the past.

“What you’ve done is disrespected the community by not giving people the chance to absorb the news and weigh in on it,” Jacobsen said. “You can’t do that to the people.”

Zoo spokeswoman Pamela Baker-Masson said the short notice is about the animals, not the people. The keepers would not be able to maintain an open exhibit and take proper care of the invertebrates while also working to find them new homes. By closing, they can focus on finding safe places for the animals to go before moving on to new jobs within the zoo.

Some invertebrates will go to other exhibits at the National Zoo and some to other zoos. Because of the short notice, there is little certainty as to which animals will go where, Peters said. His e-mail has been flooded with requests from other zoos’ invertebrate exhibits, asking how they can help and what animals they might be able to take.

Many of the animals with short life spans, including the cuttlefish and butterflies, will die before they can be moved. The employees call it “living out their natural lives” at the zoo. Just like the octopus, and now, just like the exhibit itself.