Bedbugs, largely eliminated from developed countries after World War II, are back, and harder to kill than ever. The less-than-quarter-inch bugs and their miniscule eggs live in mattresses, books, crevices in the floor. The little suckers (pun, alas, intended) can go more than a year without feeding. And unlike termites, which cluster in the thousands, bedbugs can make trouble in very small numbers; if a single female survives an extermination, she and her hatching eggs will reinfest the space. Pest-control companies consider bedbugs their biggest challenge. After the banning of DDT and other harsh pesticides, exterminators have had to rely on something called Integrated Pest Management, an “environmentally sensitive,” multipronged approach. They can, for example, bake bugs to death by warming a room to 130 degrees using industrial-strength heaters; use mega vacuum cleaners to suck the bugs out; or apply Cryonite, a carbon-dioxide snow that freezes the fluids in the insects’ cells, causing instant death.

Bedbug dogs don’t actually do anything to bedbugs. But if the idea is to use less pesticide, dogs may be your best bet. A controlled experiment by entomologists at the University of Florida found that dogs were 98 percent accurate in locating live bedbugs in hotel rooms. In a hotel or apartment building, dogs can determine which rooms require attention, avoiding the telltale stench of mass fumigation and saving thousands of dollars by treating only the affected rooms. (Not that the dogs are cheap: they typically cost about $325 an hour.) According to recent field research, one trained dog-and-handler team is more effective at detection than trained humans alone, and accomplishes the job in significantly less time.

“You see this?” says John Russell of New Jersey’s Action Termite & Pest Control, pointing into an overstuffed Manhattan closet where one of his dogs, a black Lab named Sara, has indicated a problem. “Clutter! That’s why bedbugs are so hard to find.” The apartment’s tenant, who has lived in his one-bedroom for 34 years, hovers nearby. When Sara noses one of the many jackets within, the tenant grabs it. “I’ll just throw it out,” he says, ushering the garment into the hallway.

Sara isn’t one of Peruyero’s dogs, but a graduate of a competing outfit, the Florida Canine Academy, which claims to have been the first to enter the bedbug business, and also certifies teams to detect bombs, drugs, money, weapons, termites, and arson. Florida Canine’s trainees, selected for their work ethic, drive, and desire to please, are taught to gesture with their nose, because, “dogs who give the paw,” the owner, Bill Whitstine, says scornfully, “can scratch furniture or end up spreading the bugs around.”

Rival trainers commonly accuse each other of failure to teach dogs to distinguish between live and dead bugs. The National Entomology Scent Detection Canine Association sprang up in 2006, partly in response to “false alerting” problems among bug-sniffing dogs. “We were really concerned that a few dogs improperly trained could tarnish the whole industry,” the president, J. Louis Witherington, told me. Still, disagreement persists about the best way to train and accredit bedbug dogs.

“A lot of programs have been successful training narcotic dogs, bomb dogs, arson dogs,” Peruyero says. “But it’s a totally different world with bedbug dogs. The only thing tougher is training dogs to detect melanoma.”