The dodo is an iconic animal, made famous by the humans who wiped it out. Yet we don't really know what it looked like.
Not a single bird was preserved in its entirety, so the models on display in museums are all best-guess reconstructions. Their overall shape is guided more by 17th-century art than science. The feathers are from chickens and pigeons. Even the few skeletons that remain are medleys of different individuals.
The one specimen that came close to being preserved is now just a mummified head and a tattered foot. After its kin went extinct, this specimen was slowly eaten in a storeroom in the Ashmolean Museum in Oxford, UK – probably by insects.
If that sounds like the sort of ludicrous blunder that couldn't possibly happen today, think again. The world's museums are fighting a constant battle to preserve their specimens, in the face of marauding pests determined to eat them up. It's a war fought in secret, using a host of techniques including chemical weapons and gigantic freezers. And it's a war at least partly of our own making.
The first comprehensive anti-insect pest strategies were proposed in the 18th century. In 1772, John Coakley Lettsom set out how to protect collections from insect attack. In The Naturalist's and Traveller's Companion, he suggested using toxic metals such as mercury and arsenic to preserve natural history.
The use of toxic metals has waned since Darwin's day
Thanks to Lettsom, many crucial collections can still be admired today. That includes the butterflies of Henry Walter Bates, the beetles of Alfred Russell Wallace, and even the birds of Charles Darwin. "He almost certainly used this book," says David Pinniger, an entomologist and pest management consultant.
However, the use of toxic metals has waned since Darwin's day, and over the last two decades many pesticides have been banned. That means we need new tricks.
Carpet beetles are some of the worst offenders. One example is the Guernsey carpet beetle, whose wing covers look like tiny Rorschach inkblot tests. Their hairy larvae, known as "woolly bears", snaffle up textiles, fur, and feather.
Meanwhile, the "museum nuisance beetle" tends to eat other insects, making them the bane of dried insect collections.
Curators were providing the beetles with free meals, free rides and new homes
In the 1980s and 1990s, biscuit beetles were becoming an increasingly problematic species across the UK. Also known as drugstore beetles due to their habit of eating pharmaceuticals, their small white larvae can chew through foil, plastic, or paper if trapped in packaging.
They also have a penchant for the starchy seed heads of centuries-old dried plants.
Also, as they eat they sometimes hitch a ride. When herbarium specimens were transported from museum to museum, the beetles would go with them, alighting at each destination in the search for food.
In short, curators were providing the beetles with free meals, free rides and new homes. "That's when they decided to find a way in which we can treat the herbarium collections without chemicals, safely," says Armando Mendez, coordinator of the Integrated Pest Management programme at the Natural History Museum in London.
The best option, previously used on historical textiles, was deep-freezing. Subjecting plant and animal specimens to temperatures of -30°C for 72 hours ensures that any insect eggs, larvae, or adults are killed.
Today, the Natural History Museum in London uses a freezer that is measured in mammals rather than metres. "We obviously wanted to treat everything," says Mendez. "But the giraffe and the elephant… there was no way we could build a freezer here for them. So we went for the next one, which is a rhino."
So much for beetles that eat museum specimens. But some insects don't tend to damage the specimens themselves. They just erase the information we have on them.
Silverfish are well known across the world, thanks to their metallic carapaces, long antennae, and fish-like movements. The insect group that they belong to has been around for over 400 million years.
You lose the metadata
But in recent years, they have developed a fondness for the ink on museum labels, scraping letters away like a living backspace button.
"The old inks are all organic-based," says Mendez. "[They] are very nutritious to them."
The specimens remain pristine, but the information detailing where it was from, when it was collected, and who collected it is eaten. "You lose the metadata," says Mendez. "That is a devastating loss."
These labels are used widely, so even inedible fossils, minerals, and pottery need protection.
We now have them nailed as soon they start coming in
Fortunately, serious damage from beetles and silverfish is rare. Silverfish only thrive in damp conditions, so they're fairly easy to control. What's more, in the 1990s a dedicated cadre of entomologists started focusing on beetles.
"We understand their behaviour," says Mendez. "We now have them nailed as soon they start coming in. It was pretty easy."
Then the moths arrived.
The webbing clothes moth is probably the reason you have holes in your old woolly sweaters. But in museum collections, "they are a different kettle of fish," says Mendez. For one thing, if it's warm they fly around the museum's labyrinthine corridors, making them hard to track.
They eat the hairs of mammals and the feathers of birds
They also like the dark side, literally; they will lay a clutch of up to a hundred eggs on the backs of specimens.
The eggs hatch out of sight, and the larvae start to devour anything containing animal protein. They eat tapestries. They eat wool. They eat the hairs of mammals and the feathers of birds, turning a bear into a bare bear, an eagle into a bald eagle, and a bearded vulture into a vulture.
With year-round central heating, these moths multiply quickly. "[The species] lays an awful lot of eggs, goes through a fairly short life cycle, and you can get in real problems in a hurry," says Thomas Parker, the owner of Pest Control Services Inc in Kennett Square, Pennsylvania. He says they are "the number one public enemy in museums" around the world.
That said, at least the moths only threaten the specimens. Termites threaten the museum buildings themselves.
These insects are so devastating because of their unusual biology. Unlike pretty much every other animal, they can eat and digest cellulose, the main constituent of wood. Since wood is often the main constituent of our buildings and furniture, hungry termites can be a problem.
They kind of look like deflated American footballs
Drywood termites form small colonies composed of workers, soldiers, larvae and the queen or queens. They can all live entirely within a chair or a table.
They also leave trademark indications of their presence. As their name suggests, these termites need to conserve water, and this makes their poo, or "frass", quite distinctive.
"They kind of look like deflated American footballs," says Parker. The termites push these faecal pellets out of little "toilet holes" in the wood.
Termites that live underground are less obvious. They build colonies that can house millions, and devour a building's walls, floors, and foundations.
"When they start getting into more high-value historical buildings, it becomes quite an issue," says Nan-Yao Su of the University of Florida in Davie.
As the wooden parts of a building are eaten by termites, its historical value drops. "You cannot replace them with another piece of wood that old," says Su.
In the spring of 1994, for example, eastern subterranean termites were found feeding under the feet of the Statue of Liberty. Separated from the mainland by the Hudson River, Liberty Island was termite-free until reconstruction works started in the 1980s. When lumber was ferried over, so were termites.
Swarms of sexed-up insects regularly mobbed visiting tourists
The statue itself is made of copper and is safe. But the pedestal, which houses a museum, was originally a fortress, a relic of an invasion that didn't happen, and its interior is made of wood.
"That's what they were eating," says Su. Like worms through an apple, three colonies ate their way through the fortress's walls and floors, and some of the museum's display cabinets. The infestation was so bad that the museum was temporarily closed.
The colonies also released thousands of winged males and females, known as alates, whose sole purpose is to reproduce and start new colonies. These swarms of sexed-up insects regularly mobbed visiting tourists.
To get rid of the infestation, Su and his colleagues used the termites' foraging behaviour against them.
Although most of the colony remains underground, workers occasionally search for food on the surface. They bring any morsels back to the colony and pass them around, mouth-to-mouth. This behavior is called trophallaxis, and ants, bees, and wasps all do it too.
Okay, slap this bait on top of it and see if they'll eat it
"They spread the food to each other very quickly," says Su. "They have a common stomach, so to speak."
So the researchers laced paper towels, which the termites like to eat, with insecticide. Su sums the plan up as "Okay, slap this bait on top of it and see if they'll eat it, take it back to the colony, and kill them all."
It worked. The insecticide prevented the termites from making chitin, the main component of their exoskeletons. When the termites moulted, they could not grow another protective coat. Naked and squishy, they died.
This above-ground baiting system, commercialized as Sentricon, has taken off. "It is probably the number one [in termite control], as of 2014, in terms of commercial sales," says Su.
The trouble is that humans are encroaching onto their habitat
Sentricon has been used to exterminate subterranean termites that were infesting Fort Christian, a U.S National Historic Landmark in the Virgin Islands. Similar sentries have been established at the White House and the Capitol Building in Washington D.C., Independence Hall in Philadelphia, and Iolani Palace in Honolulu, as well as in thousands of homes.
Away from human settlements, termites are "keystone organisms", because they can unlock the vast amounts of energy stored in the woody fibers of plants. By doing so, termites help support many other species.
"They are very, very beneficial insects," says Su. There are more than 3,000 species in the world, and only around 80 are considered serious pests.
The trouble is that humans are encroaching onto their habitat and using their food as a building material. "Of course the termites are going to find something to eat," says Su. Increased human activity is the problem here.
The accidental introduction of termites to Liberty Island was a local example of a global phenomenon. By travelling around the world, we have been modifying ecosystems for centuries, transporting animals and plants into faraway lands.
Biscuit beetles are known from 3000-year-old Egyptian tombs. They were probably native to the Mediterranean, before being ferried around the world in ships carrying herbs, spices, and dried grains.
"The Romans had problems with pests," says Pinniger. "We've got examples of Roman textiles which are damaged by moths."
This problem is getting worse.
Perhaps most devastating is the spread of formosan subterranean termites.
It's pretty much found in the entire south-eastern United States
Also known as "super termites", these insects breed incredibly fast. They are native to China but were introduced onto the Hawaiian island of Oahu in the 1800s by the sandalwood trade. Since then they have spread onto all the other major islands of the archipelago and is Hawaii's most economically damaging pest.
In the 1950s, the termites turned up in Charleston, South Carolina. Colonies have been popping up in nearby states ever since. "It's pretty much found in the entire south-eastern United States right now," says Su.
On closer inspection, even species that seem to be indigenous often turn out to be recent arrivals.
For example, webbing clothes moths are now commonplace across Europe. Yet the Swedish botanist Carl Linnaeus didn't mention them in his classic 1758 book Systema Naturae, in which he exhaustively listed all the species known at the time.
We've given them a fantastic environment
"He didn't know it was a species," says Pinniger. They may have arrived in Europe during Victorian times, perhaps on the backs of animal skins from South Africa.
Webbing clothes moths are one of the species that have flourished in ecosystems shaped by humans. Such species are known as synanthropes.
"We've given them a fantastic environment," says Pinniger. "We've given them a heaven."
As long we keep accidentally moving species around the planet, there will always be new pests trying to eat irreplaceable artefacts. This is one problem that we keep inadvertently making worse.