Bed bugs have made a huge comeback in the U.S. since the 1990s. Today, the blood-sucking insects are found everywhere from cheap motels to mansions.

One reason for the resurgence may be the federal ban on D-D-T, a pesticide that went off the market in 1972.

Since then, pest control technicians have used more environmentally friendly treatments, including pyrethroids [pie-REETH-roids]. These are synthetic compounds similar to chemicals found in chrysanthemum flowers. They block nerve impulses and cause paralysis.

Unfortunately, many bed bugs now shrug them off.

A study recently published in the journal P-L-O-S One helps explain why.

The researchers studied two bed bug populations. One was resistant to pyrethroids. The other was not.

The scientists took samples from both groups and exposed them to two pyrethroid insecticides. Killing the resistant bed bugs took up to 5,000 times the amount of pesticide needed to wipe out the vulnerable group.

When the researchers compared gene sequences from both populations they found four genes that were overexpressed in the resistant bed bugs. These genes produced enzymes that counteracted the paralyzing effect of pyrethroids.

What does this mean? Well, it appears that our efforts to control bed bugs caused a quick evolutionary response. Bugs that produced greater-than-average amounts of the protective enzymes survived pyrethroid treatments. The survivors multiplied, and further treatments selected the offspring with the highest enzyme production.

The good news is, these findings may lead scientists to develop new treatments the enzymes can’t stop.

Of course, the bed bugs may be able to keep up this chemical cat-and-mouse game indefinitely.

But that doesn’t mean we should stop trying to win it. After all, who wants to crawl into a warm cozy bed infested with bed bugs?