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...