Bed Bugs Don’t Need Beds, or Humans, to Survive. They Never Did…

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The rise of bed bugs preceded modern humans by at least 100 million years. They survived the extinction that killed the dinosaurs. Could they outlive us all?

By Katherine J. Wu   May 16, 2019

Nova.jpgDon’t be fooled by their charming name: Bed bugs don’t need beds to set up shop. These intrepid insects will colonize pretty much any place where people pile up, including hotels, movie theaters, libraries, even the occasional subway—ready and waiting to ruin a human life with their bloodsucking mouthparts and death-defying durability.

It’s easy to dismiss bed bugs as loathsome pests that exist to make humans miserable. But in reality, bed bugs predate humans by leaps and bounds, making us the unwanted interlopers that first crossed into their turf.

According to a newly mapped bed bug family tree, these puny pests have been guzzling the blood of other animals for more than 100 million years, long before the rise of both modern humans and bats, their most common host. The research, published today in the journal Current Biology, shows that the bed bug timeline stretches further back than even the mass extinction that wiped out 75 percent of Earth’s plant and animal species, including all dinosaurs, 66 million years ago.

The surprising longevity of bed bugs means we’re no longer certain of the identity of these bloodthirsty buggers’ first host. But the study’s findings could still offer clues on how bed bugs once made the jump to humans, and if that transition will have an encore act in the future.

“Bed bugs didn’t evolve on humans,” says study author Michael Siva-Jothy, an entomologist and evolutionary biologist at the University of Sheffield in the United Kingdom. “We just happen to be their current host at the moment—which means they’re very good at what they do.”

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Bed bug bites are caused primarily by two species—Cimex lectularius and Cimex hemipterus—which pierce human skin and drink blood with their sucking mouthparts. Luckily, neither is thought to transmit disease. Image Credit: smuay, iStock

The scourge of bed bugs on humankind is believed to stretch back to the very dawn of our species. But only three species—Cimex lectulariusCimex hemipterus, and, less commonly, Leptocimex boueti—routinely spend their nights supping on human blood. At least 100 other types of bed bugs exist worldwide, feeding mostly on bats and, to a lesser extent, birds, and researchers still don’t have a good understanding of these insects’ origins, and how species have split and diversified over time.

To generate a more complete bed bug catalog, an international team of scientists led by Klaus Reinhardt, a molecular and evolutionary biologist at the Dresden University of Technology in Germany, set out to amass insects from around the world.

A handful of specimens weren’t too hard to come by, arriving via the generosity of natural history museums, or scientific colleagues who had seen the team’s requests for help on Twitter. Collecting the lion’s share of the data, however, required some pretty gnarly field trips that featured amateur cliff scaling, treks through knee-deep guano, and hikes into remote mountaintop caves—all in search of nondescript insects just millimeters long.

In all, sample collection alone took the study’s 15 authors the better part of 15 years. But the result was an unprecedented collection of pristine bed bug DNA, representing 34 species hailing from 62 localities around the globe.

“It’s really difficult to collect these specimens,” says Christiane Weirauch, a systematic entomologist at the University of California, Riverside who was not involved in the study. “It’s just so cool that this team has pulled this together.”

By comparing DNA sequences across species, Reinhardt, Siva-Jothy, and their colleagues were able to trace the evolutionary relationships between the bed bugs they’d collected. The researchers then combined their data with evidence from known insect fossils to pinpoint when bed bug lineages had split in the past. And when the bed bug family tree was finally mapped, the team was met with a set of findings that flew in the face of almost everything they’d expected.

Because bats remain the most common host of bed bugs (technically, bat bugs) today, Siva-Jothy says, most researchers have assumed that the first bed bugs to scuttle the Earth also gorged on the blood of these winged mammals. Cozied up to cave-dwelling bats, bed bugs would’ve then had an easy time making the hop to our human ancestors seeking shelter some 2 million years ago, and evolved alongside the genus Homo ever since.

Neither of these theories panned out.

The researchers’ analysis now places the origin of bedbugs around 115 million years ago, during the Cretaceous—a whopping 30 to 50 million years before bats are believed to have come onto the scene. It’s not yet clear what species first drew the bed bug straw, but a good candidate might be a small, social, cave-dwelling mammal, Reinhardt says.

Others, however, aren’t ready to completely rule out bats, or at least an early bat-like ancestor. “The fossil records for [both bed bugs and mammals] are patchy…that makes it hard to make definitive statements,” says Jessica Ware, an entomologist and evolutionary biologist at Rutgers University who was not involved in the study. “It’s possible bats are older, and we’ve just underestimated.”

Some 70 more bed bug species have yet to be analyzed in this way, and the family tree could still change with the addition of new data, Ware says. “That being said, this is the first and maybe most comprehensive analysis people have done for [this group of insects].”

Regardless of where, and on whom, bed bugs got their start, it appears these insects were hardy enough to weather a mass extinction—and have remained alarmingly adaptable ever since. The researchers’ findings suggest that, throughout their evolutionary history, several bed bug species went from bothering bats to terrorizing birds and vice versa. Along the way, at least three species dipped their spindly legs into human stock. Surprisingly, all three species appear to have evolved independently, with each making a separate jump to human hosts.

In other words, we humans didn’t actually do much to shape the evolution of one of our most iconic pests, who were perfectly content binging on the blood of bats and birds. It just so happened that, when an unlucky member of the genus Homo stumbled onto their path, certain bed bugs were flexible enough to expand their palates.

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Bats were once thought to be the first host of bed bugs. But a newly mapped family tree shows that bed bugs predate bats by 30 to 50 million years. Image Credit: Mark Chappell, University of California, Riverside

There’s even a chance another bed bug species might one day develop a taste for human blood, Reinhardt says (in fact, it might already be happening). Based on the historical data, these transitions happen roughly every half a million years.

But the more pressing concern might be the enemies we already know, Siva-Jothy says. “With human populations expanding, and our reliance on animals, and the way cities grow and communicate…there will be more opportunities for the species we’ve already got to become more widespread.”

Given the stubbornness of bed bug infestations, that’s not great news. It’s enough to make us wonder if bed bugs have the apocalyptic armor to outlive us all.

We might not have made our bed bugs. But we still have to lie with them.