Infested

How the Bed Bug Infiltrated our Bedrooms and Took Over the World

The University of Chicago Press

Contents

Cryptic Insect

Meet the Bed Bug

Picture a bedroom. Maybe it's yours. Maybe the bedding is clean and crisp, a laundry-fresh comforter is tucked around the mattress, and your clothes are hidden away, neatly folded in your dresser or hanging in your closet. Maybe, instead, the sheets are twisted, the blankets askew, and your jeans from yesterday are on the floor next to the hamper. It doesn't matter. Somewhere in that bedroom, small secretive bugs may have squeezed into a crack or hole imperceptible to your clumsy eyes: the joint of the bed frame, the head of a screw in the back of your nightstand, or perhaps a fold in the lining of the suitcase that is still sitting, unpacked, in the corner. The bugs are reddish brown and flat, and are most comfortable in these tight spaces, where they spend most of their time waiting. Waiting for you.

These are bed bugs. Their knack for concealment is why entomologists sometimes call them cryptic insects, although the uninitiated often think, incorrectly, that they've never seen a bed bug not because it is good at hiding but because it is invisible to the human eye. Somehow, although our history with this ancient pest stretches back many millennia, its brief sixty-year absence from a large swath of the world shrank our impressions of its physicality to microscopic dimensions. It became both an imaginary and an invisible threat. This made the bed bug's return as a real animal that takes up space in the world—our world, our beds—all the more unsettling. But despite the bed bug's ability to hide and to seem invisible, it is not. Some who have seen one say it resembles a drop of blood with legs. Others offer less gruesome analogies: an adult bed bug is the size and shape of a lentil or maybe an apple seed. Whatever the comparison, the insect is a physical being. You can cradle it in the palm of your hand, look into its tiny eyes, and watch it march across your mattress.

While a bed bug's life may seem secret to us, it carries on the same basic routines as any other animal: it eats, seeks shelter, and has sex. For a bed bug, food is always blood. It hunts down each blood meal, as entomologists call it, every few days to a week and almost exclusively at night. From its hiding place in the bed-frame joint or the nightstand screw, it senses the carbon dioxide from your breath, the heat from your body, and, perhaps, some of the hundreds of other chemicals regularly emitted from your skin. It ventures out, scurrying across the floor, up the bed legs, and across the sheets. When the bed bug finds you, it grips your skin with clawed feet and unfolds its mouth—a long tube called a proboscis, also called a beak—to probe the flesh, seeking the best place to bite. Within the beak are the bug's upper and lower mouthparts—the maxillae and mandibles, respectively—each divided into right and left sides. When the bed bug is ready to penetrate the skin, the toothed mandibles lead the way, snipping through like scissors to make a path for the maxillae, which follow. Once inside, the mouthparts restlessly seek a blood vessel. Unlike some insects that guzzle pooled blood, the bed bug is a bloodsucker and takes its meal from blood circulating inside a living thing. Assisted by the difference between the high pressure of the blood vessel and the low pressure of its empty body, it fills like a water balloon attached to a spigot.

To find the perfect spot where the blood flow isn't too fast or too slow, the bed bug's mouth performs extraordinary acrobatics, sometimes bending more than ninety degrees as it explores the flesh. Once the bug settles on a vessel, it injects saliva packed with a cocktail of forty-six proteins. Some are anticoagulants to prevent clotting, for a blood clot would be deadly as a half-chewed hunk of steak lodged in your throat. There isn't much room to play with. The bed bug's mouth is just eight micrometers in diameter—thinner than a strand of silk, but just wide enough, as a human red blood cell is seven and a half micrometers across. Other bed bug saliva proteins act as vasodilators, which widen the blood vessels, or prevent hemostasis, which keep the blood flowing; still others have antibacterial properties or help with lubrication. Like other blood-feeding insects, the bed bug may also numb its host with proteins that act as anesthetics to help avoid detection, although no one has scientifically proved this.

An adult bed bug's bite lasts around eight minutes, during which its flat body plumps to double or even triple its original size. Young bed bugs, called nymphs, require less blood, although they need to feed at each of their five stages in order to grow. If they don't, they remain in arrested development indefinitely, or at least until they starve to death. After a bed bug feeds, it concentrates the protein-rich red blood cells, squeezing the rest of the meal—mainly a liquid blood component called sera—out of its rear mid-bite. These drops and, later, the fully digested blood meal, fall to the bed sheets and dry as black stains, a telltale bed bug mark. Sometimes, too, bed bugs leave a signature as a line of bites along a person's body, a result of several bugs biting at the juncture where the skin meets the bed sheets. ("Like pigs to the trough," as I've heard one medical entomologist describe it.)

After feeding, an adult bed bug skitters back to its bed-frame joint or screw head or suitcase, or wherever else it has made its home, at speeds of up to four feet per minute. Nymphs move considerably slower. Both find their way with specialized receptors on their fine antennae and, perhaps, in their feet, which detect chemicals called pheromones that help guide insects' social behavior, oozing from other bed bugs back at the refuge. These are called aggregation pheromones for the fact that they encourage the bugs to group together. (All bed bugs also emit alarm pheromones in times of danger to warn others away, and females may also use chemical signals to help nymphs find their first meal.) Once a bed bug has tracked down the aggregation pheromones and it is safe in its hiding spot, it snuggles in with anywhere from five to dozens of others, including both nymphs and adults. They pack in tight amongst their own eggs, cast skins, and shit, giving off a musty, fruity odor that was described in 1936 by an entomologist as an "obnoxious sweetness."

After a meal, bed bugs often engage in rough-and-tumble sex, in part because a satiated female is sluggish and her plump body makes her easy to mount. (Once, at a bar, I overheard an entomologist call the bugs "chubby chasers" for this fact.) Bed bugs are part of a club of just a handful of invertebrate classes that mate by an unusual practice called traumatic insemination, and they hold the title for the most highly adapted form, as well as the most studied. It goes like this: The male bed bug climbs onto his lover's back, his head resting on the left side of her pronotum, the outside of the first segment of the thorax that is roughly equivalent to her neck. He grasps her with the claws of his feet and tucks his abdomen so that it curves around her body, holding her in a violent embrace. At the tip of his abdomen is a hypodermic appendage called a lanceolate paramere, which is essentially the bed bug's penis. He swiftly stabs the female's underside and ejaculates into her body cavity. It's more like a shanking than a romantic coupling.

To counteract the male's stabs, the female bed bug has evolved a unique protective organ called a spermalege. On the outside, it appears as a small notch on the right side of her segmented abdomen, which physically guides the paramere to the correct spot—the male may stab anywhere, but the female subtly directs his aim. Inside the spermalege, a mass of immune cells called hemocytes, analogous to white blood cells, protects the female from bacteriathat coat the paramere and helps heal her love wounds. The sperm, which have their own anti-microbial properties that may shield them from bacteria and help further protect the female, make their way into the female's circulatory system and ultimately collect in bags attached to her ovaries. There, she stores the sperm, using just a bit at a time to stretch her fertilization period to between five and six weeks. This is a particularly handy strategy if she is swept away, alone, to a new home.

Once fertilized, the female may lay five eggs a week, which can add up to several hundred over her lifetime, although just as with any animal, this varies from one individual bug to another, impacted by her circumstances, such as access to food and the temperature of her home. However many eggs she lays, she exudes a gummy substance that cements them together and to the surface where they are laid. ("Looks like mini caviar," a gruff Brooklyn exterminator once told me, although I later decided they are more like tiny grains of rice.) The female bed bug lays these eggs from a genital tract that is perfectly functional and could be used for a more traditional mating style. Yet still, the male stabs, and more often than necessary. A female bed bug needs to mate just once for every four blood meals in order to produce the highest possible number of eggs. Males typically initiate sex twenty to twenty-five times that often. If a population of bed bugs has too many males, they may stab the females to death in their overenthusiasm and leave them no time to heal from their wounds. Or so some scientists claim.

Entomologists have been trying to understand the bed bug's strange mating ritual for nearly a century. The answer may lie in an evolutionary biology concept called sexual conflict, where one sex of a species evolves features that increase its chances of breeding, but at the other sex's expense. Their partners co-evolve strategies to counteract these unwanted advances. This sexual arms race is relatively common. Fruit flies battle over how long the male's sperm can survive in the female's reproductive tract. Muscovy duck males have alarmingly long curlicue penises, while the females have labyrinthine vaginas that twist in the opposite direction to turn away unwanted suitors. As for the bed bug, the male's stabbing ways may have evolved so that he could better compete with his rivals; by stabbing his paramere directly into the female's body, closer to her ovaries, he might get his sperm to the target a little faster than a beau that chose the old-fashioned route. Other research suggests that the last sperm into the female's sperm bags are the first to make it to the ovaries, which means the last male to mate with a female may get to cut the paternity line. This could explain why males mate at such mad frequency. Yet another possibility is that the male's approach evolved in response to female adaptations that tried to thwart his moves. Regardless of the cause, and unfortunately for the female bed bug who lacks good resistance against over-mating, it appears that she is currently losing this particular battle of the sexes.

All this activity describes just the hidden world of the common bed bug, Cimex lectularius, which is the species that has reasserted itself in temperate climates worldwide over the past fifteen years (in this book, "bed bug" will generally refer to C. lectularius). Around a hundred related species live out shadowy parallel lives, mainly in the nests of birds or the roosts of bats rather than your hypothetical bedroom, where they feed on pigeons and chickens and sparrows and mouse-eared bats. Collectively, these bugs are called Cimicidae (pronounced sigh-MISS-uh-dee), or cimicids.

Cimicids belong to the Linnaean order Hemiptera, or the "true bugs," which is why entomologists spell out "bed bugs" as two words (by contrast, a house fly is two words because it's a true fly, while a butterfly, one word, is not). All Hemiptera have sucking mouthparts in order to puncture the outer layers of the flora or fauna on which they feed and to drain the fluids inside, whether it's the sap in a leaf or the juice in another insect or, for cimicids, the blood of a more complex animal. The true bugs' name comes from hemi- for "half" and -ptera for "wing"; they are named so for the fact that their wings form a hardened shell at the top, where they attach to the body, and a thinner membrane toward the tips. The wings of many Hemiptera form a signature X pattern when folded across their back. But cimicids have only the stunted nubs of rudimentary wings, possibly because they have adopted the simplest eating strategy an animal can have, which is to sit and wait for food to arrive. The bugs have no reason to fly because we always return to our beds, just as birds do to their nests and bats to their roosts. Wings would also burden cimicids, tangling in feathers and fur during a meal.

Other than the common bed bug, which lives primarily in temperate regions around the world, only two other cimicid species regularly feed on human blood. One is the tropical bed bug, Cimex hemipterus, the common bed bug's counterpart in the tropics. Like the common bed bug, this species recently resurged across the world, particularly in Asia, India, and Australia, the latter of which which is overrun with the common bed bug in the cooler southern regions and the tropical bed bug in the warmer north. The other is Leptocimex boueti, which feeds on bats and people in West Africa.

To the untrained eye, bed bugs, bat bugs, and the various bird bugs all look pretty much the same. They have wide-set eyes and short antennae. Their oval bodies are segmented, giving them a striped appearance, and bristle with stiff hairs, as do their three pairs of legs. Adults are dark brown and their color shifts to mahogany when they feed. Nymphs are white with eerie red eyes when they wriggle from their eggs. As they mature, they turn the color of straw and then gradually darken to brown. But while they may look the same to most of us, each has characteristics befitting life in its own unique niche.

* * *

When I first sought to uncover the secret life of the bed bug, I spent two hours on a Saturday morning on the phone with an entomologist who was studying the insect. It was the only day she had time to talk; bed bugs had taken over her life, and she worked all hours during the week studying the insect and fielding panicked calls from people with infestations.

During our interview, the entomologist told me about a book called Monograph of Cimicidae. It was published in 1966, and although some of its contents are outdated, it remains the heftiest bed bug book in existence, phone-book thick with 585 dense pages describing the seventy-four bed bug species that were known at the time it was written. When I sought a copy in 2011, it was relatively easy to find because the Entomological Society of America had issued a reprint the year before, at the height of the bed bug panic. At $74, it worked out to a dollar per species. The book started me on my much longer bed bug journey, remained a constant companion even as I dug through other papers and texts, and would pop up in places I did not expect.

Monograph of Cimicidae was written by a man named Robert Leslie Usinger, an entomologist who worked and taught at the University of California, Berkeley, in the forties through the sixties. He was also the most significant contributor to bed bug research in the last century. When Usinger wrote his tome, and somewhat still today, entomologists identified cimicid species by slight variations in the bugs' legs, bodies, and other prominent features that are indistinguishable to my naked eye. But when I flipped through the monograph for the first time, the variety from one species to another was dizzying. The magnified views of Usinger's clean ink drawings, as well as those by a few colleagues, spanned more than 150 pages. The species had their own portraits, which revealed that some bugs are long and thin while the others are short and fat; some are balding, others hirsute, and the hair of each grows in a unique pattern; antennae may stick out ninety degrees from the side of the face, or angle toward the front, or bend back to point at the insect's rear end; legs are long and spindly or short and squat or something in between; and abdomens range from thin and pointy to a near-perfect circle. Detailed figures compared antennae of many species at once, illustrating distinct lengths and shapes and constellations of hair, or lay out the differences between a series of legs, some of which are mottled and others uniformly shaded. Still other drawings compared bed bug genitalia. One series showed female bat bugs and bird bugs and bed bugs, the varying shapes and positions of their varying spermaleges delicately outlined, and another laid out the array of bed bug penises, all of which crooked to the left but differed in length, girth, curvature, and pointiness.