Like a pining lover, bed bugs will seek out your smell and snuggle up to your worn clothes when you are not around, researchers said Thursday.
This explains how these tiny, flightless, reclusive creatures have managed their meteoric spread around the world—by catching a free ride in our dirty laundry, a team wrote in the journal Scientific Reports.
"A mechanism for this long-distance dispersal has never been empirically tested," study co-author William Hentley of the University of Sheffield told AFP.
Some had thought that bed bugs accidentally fell on our clothing or luggage after feeding on our blood, then tag along home from the hotel.
But the new study showed the pests, known to be attracted to the smell of sleeping humans, actively seek out our worn clothes.
Hentley and a team tested the predilections of bed bugs in a series of unusual experiments.
Human volunteers washed themselves with a non-perfumed soap, then wore a clean T-shirt and socks for about six hours.
The clothes were placed in a sealed, airtight plastic bag before being transferred to a cotton tote bag.
Four bags—two with dirty T-shirts and socks, and two with clean ones—were placed in a room at an equal distance from the centre.
Bed bugs, fed to satiation on human blood, were then released and observed.
After four days, researchers noted the location of the bugs and found that most were on the bags containing soiled clothes.
The experiment was repeated a few times.
"Bed bugs have shown a recent and rapid global expansion that has been suggested to be caused by cheap air travel," the authors wrote.
"Our results show, for the first time, how leaving worn clothing exposed in sleeping areas when travelling can be exploited by bed bugs to facilitate passive dispersal."
Last year, research showed that bed bugs had become genetically wired to resist pesticides, further aiding their global conquest.
The common bedbug, Cimex lectularius, is found in temperate climates in the United States and parts of Europe.
It has proved especially hard to eradicate after potent poisons like DDT were banned in the United States after World War II.
By the late 1990s, the critters were thriving in New York and a 2010 outbreak saw them invade high-end apartment buildings, hotels, even clothing stores like lingerie outlet Victoria's Secret.
There has also been an explosion of bed bugs in Paris in recent years.