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Bedbugs Have Evolved to Live With Mankind

The rise of bedbugs has followed the rise of mankind living indoors; their latest resurgence illustrates the survival of the fittest.
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"Bedbugs sure is evil, they don't mean me no good. Yeah, bedbug sure is evil, they don't mean me no good. Thinks he's a woodpecker and I'm a chunk of wood.” — Bessie Smith ("Mean Old Bedbug Blues")

Bedbugs are small and sneaky. Bedbugs do nasty things. Bedbugs are also becoming more common, a trend likely to expand and worsen this spring. But none of this is new, not really. The story of the bedbugs in our lives begins no less than 4,000 years ago. It is a kind of parable about the difference between what we want and what we make. We wanted a realm inside our houses, where we would always be happy and might live forever.

Instead, we made the bedbug, a modern chimera we seem unlikely to ever really escape.

It began innocently. Once we were like the birds. The rain fell on our naked shoulders. The sun beat down on our heads. There was no inside or outside. We built our nests of sticks and mud. Then we moved out of the trees. On the ground, the world was more dangerous. Leopards crouched in the darkness between resting spots, venomous snakes hid under leaves. We sought safety, shade and cover and found them all in caves.

Caves changed the world. In moving into caves, we invented the more constant conditions of the "indoors." No matter that this particular indoors lacked an actual door, it was still the rough seed of what would come. It was the beginning of our efforts to make the place we lived "better" than everywhere else.

It was when we began to try to find even more favorable conditions for ourselves, to engender them even, that we began the process of making bedbugs from the sticks and mud of natural selection. Bedbugs belong to two or three species, depending on exactly how you are counting and who is counting. The most common species is — thanks to a modest failure of scientific creativity — the common bedbug (Cimex lectularius). Bedbugs were originally bat bugs. Their ancestors lived in caves, on bats (where most of their kin still live), and when our ancestors moved into caves, they jumped down onto us. A few found us where we slept. Those that did prospered on our blood as we prospered.

When they moved onto us, many things would have had to change for these bat/cavemen bugs. The platelets in our blood, for example, are wider than those of bats, and so the mouthparts of the bedbugs had to widen so that they wouldn’t clog up with blood. Their mouthparts changed in length, too, because of the thickness of our skin, a thickness through which their mandibles must meander to find blood vessels. Their activity patterns changed, too. Bat bugs feed during the day, when the bats are sleeping. Bedbugs, well, they had to feed at night, when we were sleeping.

Bedbugs changed so much in moving onto us, in fact, that now they are stuck. They can’t easily go back — and why would they want to? They ride us wherever we might lead them, which, it turns out, is all around the world.

Bedbugs evolved more as our culture evolved, changing as we changed and moving as we moved. Early Egypt was dense with bedbugs. Cleopatra would have had them. Aristotle definitely did. Socrates whined about them frequently.

Bedbugs came to take advantage not just of our abundance but also of the new environments we created inside our houses, environments that are similar realms of warmth and predictability whether we live in New Jersey or Cairo. Many valiant attempts were made to control bedbugs. Democritus recommended hanging the feet of a hare at the foot of the bed, presumably with no effect on bedbugs, though with negative consequences for the hare. Cyanide was sprayed around rooms. Rooms were heated to 45 degrees C, all to relatively little permanent avail.

Then, during World War II, scientists pioneered new chemicals for warfare. We used some of those chemicals, in particular DDT, around our apartments and houses in our war with pests. These pesticides appear to have controlled the bedbugs by making the indoor environment more toxic than most bedbugs could stand. This, we hoped, would be good for us. It was certainly bad for the bedbugs, for a while.

It was clear as early as 1947 that bedbugs could evolve resistance, first to DDT and then, one by one, to its chemical descendants. They evolved similar but sometimes unique forms of resistance in many different places all around the world (and in each bedbug species), which is to say that genetically they may have actually diversified. This was possible because we never, ever killed them all. We only killed the weak, and so, just as in those first caves, they evolved once again: They changed when we made them change. Recently, the inevitable has happened. These survivors have started to become abundant again, separately, in different regions of the world. We made our bed and they slept in it.

This is where we find ourselves now, reunited again with the species we have been shaping all these years, our evolutionary masterwork. The bedbugs, after their brief hiatus, seem foreign to us now. News stories call them strange or unusual, which they certainly are. The males have sex with females traumatically (by penetrating their bellies). They smell bad (an odor one scientist described as “an obnoxious sweetness”) so that even if we find them we are unlikely to try to bite them back (speaking for myself, I was never really tempted). Male bedbug nymphs compete with each other by trying to block each other’s sexy smells.

Bedbugs smell us, on the other hand, by the scent of our bodies but also, probably, the scent that the microbes on our bodies emit. All of that is weird, but it is also our fault, the consequence of the world we have created around ourselves, a world just right for us and, once again, for them.

But … you might reasonably contend that we try to control bedbugs. We chase and kill them. That’s true. But all this chasing has not done away with them. It has made them stronger, or better adapted anyway, to our ways and lives. In the process, it may have actually made them more common than they would have been otherwise had we never tried to beat them away. They may be more common because our houses have become ever more warm and because we have become ever better at ferrying them from one place to another. Also, we seem to be getting better and better at killing the other species that live around us, species other than the bedbug (and a handful of other equally sneaky beasts) that have learned to love it this way.

Ants That Eat Bedbugs!

See some of the ants that might eat your bedbugs in Manhattan (click here) or more generally (click here).


All things being equal, bedbugs would probably be more rare if we were just a little bit sloppier in controlling our environments and keeping species from coming in our door. Take the example of the Pharaoh ant.

The Pharaoh ant, Monomorium pharaonis, like bedbugs, spread with us all around the world and is now on every continent except Antarctica (though it may be there). The Pharaoh ant is a species that we have been able to exclude from our houses relatively well. It is present here and there, but no longer ubiquitous. That is bad news, bad news because the Pharaoh ant is very good at eating bedbugs. During the U.S. Civil War, Pharaoh ants cleaned a camp in Meridian, Miss., of bedbugs "in a single day." The ants could be seen carrying the bedbugs back to their small, dark queens.

Nor is this ant the only species that is good at eating bugs. So, apparently, are other species of ants, including Argentine ants (Linipithema humile), species of the ant genus, Formica, a fire ant, Solenopsis geminata, and, one presumes, many other species. Nor are the ants alone. Several species of spiders have been reported as bedbug decimators. Then there is the masked assassin bug (Reduvius personatus) that appears to turn up in houses only when bedbugs are present. It may well be a bedbug specialist, feeding specifically on the species that feed specifically on us.

In the caves of our ancestry, Pharaoh ants, masked assassins, spiders and predators more generally were present. With their small arms and mouthparts they ate at bedbugs. In doing so, they may not have gotten rid of them, but they almost certainly made them less common. They were part of a diverse food web that kept the life that plagued (and plagues) us in check, the way the mountain lions, coyotes and their kin once ate the deer that now graze densely in our yards.

This is the secret about bedbugs: From the perspective of our broad history, they are common because we are common but also because we have made decisions that have made them more common, more specialized on us and more uniquely part of our lives. They are common because we have inadvertently given them a place to live, free of parasites or predators, to dine on our ankles and then return to their hiding places, to sleep and mate in their complicated, awful ways.

What we will undoubtedly try to do when the bedbugs begin to unfold out of their eggs in the spring is to figure out new ways to spray our lives down and make the door separating inside from outside more exclusive. I would argue for the opposite, leaving the door just a little more open so that the Pharaoh ants and their kin might walk inside and do what they have been doing since long before we had coffee makers, indoor plumbing or even houses — gathering what they find, one piece or body at a time. To crudely paraphrase the Japanese poet Issa, don’t worry Pharaoh ants, I keep house easily.

In the end, we made the bedbug, generation by generation, what it is today. But we could choose to make something else, a more diverse world around us, whether in our backyards or bedrooms, a world in which there are bedbugs sometimes, yes, but also the predators that chase them from corner to corner hunting them down, the way leopards once pursued us, into caves, where this whole story started.

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