Meet the Smithsonian’s Spookiest Staffers: Flesh-Eating Beetles

This Halloween season, learn how the National Museum of Natural History’s dermestid beetle colony transforms decaying animal carcasses into spotless skeletons.

A shelf of brown boxes with white bones peeking out of the top has small black beetles crawling all over them.
The Smithsonian’s Osteo Prep Lab houses a colony of over a thousand flesh-eating beetles that work round-the-clock, feeding on animal specimens to prepare their bones for research and display in the museum’s exhibits. Smithsonian Institution

As the moon rises and the chill of October settles in, an army of Smithsonian staffers works tirelessly through the night.  But these creepy curators aren’t wearing lab coats.  Instead, they’re clad in exoskeletons as they meticulously clean the hair, feathers, and flesh off of the scores of zoological specimens that arrive at the National Museum of Natural History each year.

Thousands of Dermestes maculatus, more commonly known as flesh-eating beetles, reside behind the heavy metal doors of two bunker-like chambers at the Smithsonian’s Museum Support Center in Suitland, Maryland.  From wool rugs and books to leather and dried pasta, these intimidating insects will eat almost anything.  And at the museum’s Osteo Prep Lab, eating is their job.

Dermestid beetles are best described by their wide variety of common names, such as hide beetles, leather beetles, carpet beetles, larder beetles, skin beetles, flesh-eating beetles and taxidermy beetles.  Measuring only 1-12mm long, dermestids are capable of eating up to 5 times their body weight each day.  U. Schmidt

The Osteo Prep Lab receives an average of 50 animal specimens per month from the museum’s various research departments, meaning its freezers are never empty.  These include specimens ranging in size from colossal whales to fragile hummingbirds.

Before researchers can study the slender bones inside of a bat’s wing or museum visitors can peek under the shell of a giant sea turtle in the museum’s Bone Hall, these remains undergo a thorough cleaning process.

Osteo Prep Lab manager Ella Haigler (left) and osteo preparator Inger Toraason (right) remove the skull of a cetacean from a specimen compost bin.  While most soft tissue is disposed of, Haigler and Toraason often send skin, hair, and muscle samples to the Smithsonian’s Biorepository for long-term preservation and research. Jack Tamisiea, NMNH

The first step takes place in a large room where suction tubes snake down from the ceiling and bone saws lean against the walls.  This space is known as the necropsy lab, where Osteo Prep Lab manager Ella Haigler and osteo preparator Inger Toraason remove as much soft tissue from the specimens as possible.  Once the remaining flesh has dried out and reached a jerky-like consistency, the specimens are transported to the next step in the painstaking process: the beetle colony.

While entering a room full of flesh-eating beetles as they devour a decaying feast may sound like a horror movie scene, the experience is far more extraordinary than eerie.  Strips of fabric act as insect highways between old military trunks that hold withered whale skulls and rows of rib bones.  The specimens rest on thick layers of beetle exoskeletons — a stark reminder of the colony’s size — as hungry larvae crawl in and out of empty skeletal eye sockets.

The skulls of two cetaceans rest in the Osteo Prep Lab’s free-roaming beetle chamber.  While the live beetles are not a threat to humans, the mixture of dung and exoskeletons that collects at the bottom of the containers can cause an allergic reaction with prolonged exposure. Emma Saaty, NMNH

Using beetles for museum preparation is a time-honored tradition that has been an integral part of Smithsonian operations since the 1800s when the colony resided downtown in a small shed next to the museum.  Researchers from around the world penned manuscripts comparing specimen preparation techniques, and dermestid beetles consistently came out on top.

“Dermestid beetles are faster and more delicate than any other method of bone cleaning we could use, and their tiny bodies can get into nooks and crannies much more efficiently than we can,” said Haigler.  “They’re our unsung heroes, and we couldn’t do the job without them.”  A specimen that could take days to clean by soaking in water or picking by hand takes the beetles a matter of hours, allowing the lab to keep up with the museum’s abundant requests.

The remains of birds and squirrels are being cleaned by the beetles in separate boxes to ensure that the bones are not mixed.  Depending on the size of the specimen, it can take the beetles anywhere from a few hours to multiple weeks to clean a complete skeleton. Emma Saaty, NMNH

The Smithsonian’s beetle colony is almost completely self-sustaining, and aside from a strict temperature requirement between 79-81 degrees Fahrenheit, the colony is fairly low maintenance.  However, the beetles can be picky. So Toraason and Haigler have developed numerous tricks to make their seemingly macabre meals more enticing.  Spraying ammonia or oil made from whale blubber onto the specimens often gets the beetles’ attention, but a coat of bacon grease never fails to get the colony interested in even the most repugnant remains.  

The spine-chilling and nose-wrinkling experience of the beetle chambers eventually leads every Osteo Prep Lab visitor to ask the same question: “What if the beetles escape?”  While the lab is housed in a building completely separate from the rest of the museum’s storage, the isolation has very little to do with the safety of humans.

“I use my bare hands to move the beetles around all the time,” said Toraason, gathering a handful of wriggling insects with ease.  “They won’t have any interest in you unless you are very dead and very dry.  We are very fond of them out here, and they are much less scary than you would think, for flesh-eating beetles.”

Gino Nearns, a research entomologist and the museum’s curator of dermestids, agrees that the beetles are harmless to humans.  The main concern is that they are a pest threat to the rest of the Smithsonian collections.  “Dermestes maculatus are already native to the United States, and they are everywhere,” said Nearns. “So, we are not trying to contain them from getting out into the environment, but we definitely don’t want them in the collections with the other animal specimens that they would love to eat.”

The National Museum of Natural History’s Entomology Department houses a global collection of dermestid beetles with specimens going back 120 years.  With only 1800 known species, dermestids are a small but extremely populous family of beetles that can be found in almost every country in the world.  Emma Saaty, NMNH

Despite their frightening taste, Nearns emphasizes the important role that flesh-eating beetles play in their environments.  As natural recyclers, they can be found almost anywhere in the world, removing dead and decaying tissue from their ecosystems to aid the last stage in the decomposition process.

"They’re our unsung heroes, and we couldn’t do the job without them."  — Ella Haigler, Osteo Prep Lab manager

After the beetles have had their fill, the freshly cleaned bones are taken to the processing lab where they are soaked in ammonia to remove any grease and remaining pieces of flesh.  A mesmerizing line of shelves holds rows and rows of immaculate skeletons, ready to be sent back to the museum.

Although not a speck of flesh remains, the final skeletons maintain a slight yellow tint that illustrates the natural preparation methods used by Haigler and Toraason.  Any bright, white bone in a museum collection has likely been cleaned with peroxide. But the Osteo Prep Lab avoids any chemical methods that might degrade the bones and render them ineffective for biological research. 

Maintaining the beetle colony and using only natural preparation fluids is both challenging and time-consuming, but for the museum’s osteo preparators, it’s a worthwhile endeavor.  “The Smithsonian Vertebrate Zoology Department prides itself in having the cleanest natural skeleton collection in the country,” said Haigler.  “Our lab is considered a research standard, and we want to uphold that title.”

While many specimen preparation techniques completely disarticulate the skeletons, dermestid beetles keep the bones together.  This makes the remains easier to keep track of and causes less damage to the smaller, more delicate specimens. Emma Saaty, NMNH

Spending every day in a lab full of flesh-eating beetles may seem like a living nightmare to some, but Haigler and Toraason’s work has had an immeasurable impact on both the Smithsonian Institution and the global scientific community.  While a small percentage of the Osteo Prep Lab’s skeletal specimens will go on display in the museum’s exhibits, the vast majority will be used as research specimens, helping museum scientists answer some of nature’s biggest questions.

“These animals have a purpose, and they help us to see how populations are trending, how species ranges are changing, and what threats they are under,” Toraason said.  “Processing these bones is critical because they will teach us about the world and help us to protect these species in the future.  Thankfully, our beetles are always up to the challenge.”

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