Some bed bug watchers have estimated that populations have jumped by as much as 500 percent in recent years, and a 2010 survey found that 95 percent of exterminators in the U.S. had reported taking care of at least one bed bug infestation in the past year, according to Time Magazine Healthland reports.

Experts say that the increase in international human travel, along with the bugs' growing resistance to insecticides, is largely responsible for their resurgence. Now researchers have figured out one reason the critters are so hardy: they can inbreed, quite robustly, for generations. (There are a few other insect species that can do this, notably among them cockroaches.) So all it takes to infest an entire apartment building, for example, is one single mated female that hatches her offspring; after that, the brothers and sisters can mate with each other and keep the population booming.

"For the vast majority of insect species, inbreeding is detrimental," says Coby Schal, a professor of entomology at North Carolina State University, who presented his findings on bed bug inbreeding at the American Society of Tropical Medicine and Hygiene conference in Philadelphia. "'Inbreeding depression' occurs, because it leads to mutations that have deleterious effects and eventually kill off the population. But some colonizing species such as cockroaches and bed bugs are resistant to inbreeding depression because they have little opportunity to breed with other populations that might be some distance away — bed bugs can't fly — so they've evolved the ability to withstand extensive inbreeding without deleterious effects."

Since most of the bed bugs infesting the U.S. today are the resilient members of their species — resistant to the pyrethroid insecticides that are commonly used to get rid of the bugs worldwide — their inbreeding only serves to spread their chemical resistance. Once these insects seed an infestation in a building, treating them with the standard bug spray might not get rid of them. The only hope is that one of the 300 insecticides registered with the Environmental Protection Agency for use against beg bugs might do the trick.

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