The Secret Life of Bed Bugs

Although the urban bed bug Cimex lectularius was once so much a part of people’s lives in this country that a 1905 book of Modern Medicine called it “too well known to require description,” bed bugs made what seemed to be a clean exit from the scene after World War II, thanks to better sanitation and pesticides.

But unless you’ve been under a rock (not, incidentally, a particularly good place to avoid bed bugs, which like to hide in small, dark places) for the past few years, you know these critters are making a serious comeback. A good friend of mine was visiting from New York City some months ago, and people, I nearly put him on the first jet out of Chicago when hours after he arrived he started to scratch thoughtfully at himself, wondering aloud if maybe his apartment was one of the thousands in Manhattan now estimated to be infested by bed bugs every year.

Turns out he was mostly kidding, but ever since I listened to the most disturbing episode of This American Life ever, featuring a family left terrorized by nocturnal persecutors that can balloon from a mere quarter of an inch to three times that size after they feed ON HUMAN BLOOD—I’ve been a little bed bug paranoid. Also, they’re clinging, wingless insects, so it’s not uncommon for them to hitch rides across the country on clothing and luggage.

Enough about their lust for plasma and their savvy travel habits. Let’s talk about bed bug sex. Because Swedish entomologist and pheromone expert Camilla Ryne has just published a new paper adding to a rich store of scientific knowledge about what these diminutive vermin get up to in the sack (so to speak), and I can’t wait to tell you about it.

Here’s what we already knew. First, there is the brutal way male bed bugs inseminate females. The pen may be mightier than the sword, but this is one Romeo who isn’t writing any love letters. Instead, the male bed bug waits until a female has just fed (because only then does she have the energy to produce eggs), mounts her, and pierces into her abdomen with what might as well be a sword. A stabby, seed-bearing sword that will actually leave a scar.

The process, which scientists describe with no attempt at euphemism as “traumatic insemination,” means males can ensure a definitive answer to the niggling “Who’s your daddy?” question. For once the sperm has been injected directly into the female’s bloodstream, it travels through her internal cavity, arrives at her reproductive organs, and fertilizes her eggs. Fortunately for them, females aren’t without a counter-adaptive feature. The spot on their shells where they’re normally pierced has evolved to be thicker (to minimize injury), developed a special notch (to make the insertion easier and more efficient), and lies over a small pocket that collects the sperm handily and allows it to diffuse slowly (reducing the risk of infection from external pathogens and loss of blood from the wound). Researchers have found that these adaptations are terrific at protecting female bed bugs and allowing them to reproduce without too much distress. I find myself cheering on the lady bed bugs...but is their resilience a good thing? Shouldn’t I be rooting for the whole species just to stab each other into oblivion? Nature is so confusing.

This brings me to the second totally wild thing about bed bug sex. Males don’t just go after females with their keen penises. It’s kind of hard for them to tell who’s who, apparently, so if another male has just fed and is all attractively red and engorged looking, they’ll try to stab him, too. Scientists don’t think this is an act of aggression or dominance, although at least one National Geographic video suggests it may be a devious means of making your rival carry your sperm for you. Most researchers have simply concluded that sex is sort of a process of trial and error in the bed bug world. Oh, I see you’ve eaten recently. Let me stab you with my giant penis sword and see if babies result!

This is a rather alarming state of affairs for male bed bugs, because they don’t have the protective adaptations females have, and can be quite severely injured by a mistaken romantic conquest. Evolution, however, is merciful. What Ryne has just shown is that male bed bugs do have a way of shielding themselves from unwanted advances: perfume.

When mounted by another male, a panicked bed bug can release a storm of alarm pheromones that are the chemical equivalent of frantic hand-waving and cries of “Dude. DUDE! Stop harassing me. I ain’t no lady!” Ryne tested her hypothesis by painting over the male pheromone glands, preventing them from kicking up a stink when attacked. This increased the incidence of male-on-male mounting. She also collected the pheromone and spritzed it on male-female couples in the act of love, which had the effect of making the male bed bugs dismount in a hurry.

Ryne says the scent is strong enough that she can detect it herself: a faint, distasteful odor of almonds. This is, incidentally, also how cyanide is supposed to smell. Coincidence? Probably. But if you were being attacked by someone who wanted to bayonet you in the stomach with some sperm, I’d say you couldn’t be blamed for being in a killing mood.

Apparently we’re rather fond of creepy things.