Little Fury Bugs

Sex lives are a funny thing, particularly when you’re talking about bed bugs. Did I say funny? I meant insane. These wingless insects in the family Cimicidae win the award for the most depraved sex in all of the animal kingdom.

If you’re familiar with these blood-suckers, which I truly hope you are not, then you probably have encountered the common bed bug, Cimex lectulariuswhich feeds exclusively on human blood. To dine at their favorite restaurant – you – they must live in and around human dwellings (termed synanthropism).

Bed Bug Nymph Cimex lectularius)   Photo Credit: Centers for Disease Control and Prevention

Common Bed Bug Nymph (Cimex lectularius). Photo Credit: Centers for Disease Control and Prevention

What better place than your bed? You are bound to spend roughly a third of your life there, so they will always find you. And assuming you are like most humans and sleep at night, you are an easy target because these parasites are mostly active at night. They’re also teensy weensy and so can go undetected. That is, until you wake up with itchy rashes in your nether regions and beyond. But while their habitat is pathetically predictable, their sexual escapades are not.

It’s called traumatic insemination, and it is just as terrible as it sounds. Using a specialized external copulatory organ, the male pierces the female’s body and inseminates into her body cavity through the wound. The sperm then enters a special sperm receptacle inside the female before migrating to her ovaries to fertilize her eggs.

Male bed bug (top) traumatically inseminating a female bed bug (bottom). Photo Credit: Alex Wild

Male bed bug (top) traumatically inseminating a female bed bug (bottom). Photo Credit: Alex Wild

Imagine it – a knife for a penis that stabs you in the abdomen all in the name of baby-making! One cool feature of this male organ is that it bears chemosensors that allow it to detect whether or not the female is a virgin.

Male Bed Bug Copulatory Organ (Photo Credit: Andrew Syred)

Microscopic image of the male bed bug’s piercing copulatory organ. Photo Credit: Andrew Syred

This coercive male mating strategy is how all cimicids mate, despite the fact that females DO have genitalia. What likely once served as a means for mating now only functions for egg laying.

Such extraordinary abdominal wounding  is undoubtedly a form of sexual conflict (see this post) and is very costly for females. In addition to shortening their lifespan or possibly even resulting in their death, female bed bugs must deal with enhanced risk of infection through the wound. And you thought you had it bad!

How might females deal with such bodily injury? In some species, females may reduce such injury through their behavior – by moving their abdomen to either resist the male or control where he pierces her. In other species, unique structures have evolved. Some females have developed a special site on their abdomen as well as specialized grooves to help guide the male as he traumatically inseminates her.

Site on female bed bug's abdomen for male insemination. (Photo Credit: Stutt and Siva-Jothy 2001)

Site on female bed bug’s abdomen for male insemination. Photo Credit: Stutt and Siva-Jothy 2001

Female abdominal grooves that guide male's piercing copulatory organ. Photo Credit: Andrew Syred

Female abdominal grooves that guide male’s piercing copulatory organ. Photo Credit: Andrew Syred

These structures, in addition to the presence of a sperm receptacle, may reduce the amount of injury that a male is able to inflict and, subsequently, the costs of such bodily trauma.

So that’s the crazy truth about bed bug sex. They’ve been a pest to humans for thousands of years, and yet only recently have their sexual exploits been discovered. All the while, they were right under our pillow!