If you wander into the Ralph M. Parsons Discovery Center at the Natural History Museum and look up, you might think you've entered the Twilight Zone.
Hanging overhead, next to the skeleton of a finback whale, is what some staff members call "a fantastic dragonfly." But these staffers (jaded, no doubt, from working near all those dinosaur skeletons) call the dragonfly fantastic not because it's 18 feet long but because Yoshinori Shimazu took artistic liberties in carving its tail.
Thirty-three enormous wooden insects created by the Japanese artist are on display in the Discovery Center, a museum gallery devoted to hands-on exhibits and activities for children, through the end of the year.
This Sunday, admission to the museum is free.
Visitors can roam through all the life-science, earth-science and historical displays, and at 2 p.m. Gretchen Sibley, museum education specialist emeritus and honorary archivist, will give a slide-show lecture on the museum's history.
The free-admission day culminates a yearlong 75th-anniversary celebration. Sibley began working as a science instructor in 1946, "retired" in 1976 and is completing a book about the Natural History Museum.
"She knows more about the museum than anyone I've ever met," museum spokeswoman Ellen Girardeau said.
Three docent-led tours are available (at 11 a.m., noon and 1 p.m.) and a special exhibit, "The Museum at 75: A Retrospective," illustrates the institution's history through photographs, documents and artifacts. Among those artifacts is the museum's first acquisition: a tiny nest containing four finch eggs (one broken) found in the San Gabriel River bottom in late 1911.
Items on display in the retrospective "aren't all our oldest, but in many cases they're the best," said Tom Sitton, assistant curator. Also included in the show are a sabercat fossil head, a Galapagos tortoise skeleton acquired in 1915 and a restored 1912 Yale motorcycle.
In other galleries, special shows include "Famous Diamonds of the World," which features the Smithsonian Institution's Eugenie Blue diamond and Marie Antoinette earrings, and "Lost and Found Traditions: Native American Art 1965-1985," a large exhibit of contemporary Indian artworks.
Junior visitors usually are fascinated by the permanent display of dinosaur skeletons near the museum's main entrance, according to Girardeau.
"Megamouth," a plant-eating shark preserved in a big glass case, is also popular. "Kids really love this; it's just gruesome enough," Girardeau said. Caught in 1984, the shark is believed to be the only Megamouth on display anywhere.
In the afternoon, Sibley's hourlong talk will cover the museum's life story, from the laying of its cornerstone in 1910 and the grand parade that marked its opening on Nov. 6, 1913, to the present. Sibley has been organizing the museum's archives ever since her retirement.
These days, with about 300 employees and a $15.7-million budget, the museum is establishing more educational outreach programs and is revamping many exhibits. Its bird display, closed until 1990, will eventually feature "robotic birds and ecosystems you actually walk through," Girardeau said.
Permanent-exhibit areas open to the public Sunday include displays on American history, African and North American mammals, marine life, the chaparral environment, California history, antique autos, California fossils, gems and minerals and, of course, the dinosaurs.
The museum, at 900 Exposition Blvd. in Exposition Park, will be open from 10 a.m. to 5 p.m. The Discovery Center's hours are 11 a.m. to 3 p.m. All-day parking is $1 at Menlo Avenue and Exposition Boulevard.