Deep in the labyrinth of the American Museum of Natural History, past the giant suspended blue whale and the first floor’s Alaska brown bears, is an unobtrusive locked door. On it, there is a small sign.

“Bug Colony.”

Behind the door, accessible only to a handful of museum employees, thousands of flesh-eating dermestid beetles toil around the clock handling a task of specimen preparation that even the museum’s best trained specialists cannot.

They eat the meat off animal skeletons, leaving only clean bones behind.

Since many skeletons are too fine to be cleaned by human hands, the museum’s osteological preparation team turns to the six-legged staffers to prepare them for research and display.

The work is carried out in three gray wooden boxes the size of footlockers that house the colony. They are lined with stainless steel and their flip-up tops reveal beetles swarming the earthly remains of various small animals, mostly birds. They feast upon the gobbets of flesh clinging to the carcasses.

The room is pervaded by the soft, crackling sound of gnawing. “It sounds like something frying, or Rice Krispies when you add milk,” said Rob Pascocello, the colony’s tender.

The beetles are tiny enough — just a few millimeters long — to crawl into the recesses of the smallest animals and nibble away without affecting delicate skeletal structures, said Scott Schaefer, who oversees the museum’s collection of more than 30 million specimens and objects.

“They do the fine, detailed work that cannot be done by hand, because it’s so delicate,” Mr. Schaefer said. “It’s gentler than boiling a specimen or soaking it in chemicals or acid.”

Museum officials say the ravenous colony has processed most of the bird collections’ more than 30,000 skeleton specimens over the decades, plus countless other forms of carrion. “They get into the small crevices and, if left unchecked, keep eating until there’s nothing left to eat,” Mr. Schaefer said.

On a recent weekday, Paul Sweet, collection manager for the ornithology department, stood in the Bug Room, and in the interest of scientific precision pointed out that its name was imprecise.

True bugs, known to their fans as the Hemiptera order, have mouthparts that pierce and suck. Beetles — Coleoptera — are typically cylindrical and have mouthparts that chew.

The colony had gone to town with those mouthparts to reduce a once-lustrous pink flamingo to a humble bone bundle. A regal snowy owl was similarly picked clean. Then there was the small skeleton in a canister, with bones tinier than toothpicks.

“That’s a songbird,” said Mr. Pascocello.

Dermestid beetles are scavengers often found in the wild on animal carcasses, and in the nests, webs and burrows of animals.

Museum officials told The New York Times in 1979 that their dermestid colony had remained self-sustaining since being brought over from Africa in the 1930s. Mr. Sweet said the current group has been around for his entire 35 years at the museum, but could not say for sure if they were the original colony’s descendants.

Either way, since a beetle’s life is only about six months, “they’re all kissing cousins,” said Mr. Pascocello. He said that while the museum was closed during the coronavirus pandemic, he “kept a backup colony in my bedroom.”

On this day, Mr. Sweet was looking to skeletonize a northern gannet, a sea bird recovered from Midland Beach on Staten Island. It had been skinned, dried, and trimmed of most of its flesh by researchers before it was handed over to the colony for finishing work.

Within minutes, the carcass was swarmed. The beetles can pick clean a small bird within a couple of days, but may need two weeks for larger skeletons like the gannet.

Mr. Pascocello once served the beetles an orangutan; Mr. Sweet once gave them an emu. But the size of the beetles’ boxes is a factor. Larger specimens must be served piecemeal, like the carcass of a feisty Cuban crocodile known as Fidel, obtained from the Bronx Zoo in 2005.

Before the pristine skeletons are boxed and cataloged, they are soaked in water and frozen for days to kill remaining beetles or eggs.

The beetles are not a threat to humans, but an infestation of the museum’s specimen collection would be disastrous. Keeping the beetles well fed discourages them from wandering away, as does a strip of Vaseline toward the top of their boxes and a sticky floor section across the room’s doorway.

If the supply of specimens should stall, Mr. Pascocello keeps some chicken around as emergency food. Mr. Sweet said he offered the colony pigs’ feet during the pandemic because it was the cheapest bone meat at the supermarket.

The gourmandising of the beetles is a reminder that important science is not always conducted in gleaming, hygienic laboratories. On the door, under the “Bug Colony” sign, is a handwritten addendum:

“Bad odors emanating from behind this door is normal.”