After waking up one night in sheets teeming with tiny bugs, Josh Benton couldn't sleep for months and kept a flashlight and can of Raid with him in bed.

"We were afraid to even tell people about it at first," Benton said of the bedbugs in his home. "It feels like maybe some way you're living is encouraging this, that you're living in a bad neighborhood or have a dirty apartment."

Absent from the U.S. for so long that some thought they were a myth, bedbugs are back. Entomologists and pest control professionals are reporting a dramatic increase in infestations throughout the country, and no one knows exactly why.

"It's no secret that bedbugs are making a comeback," said Dan Suiter, an associate professor of entomology at the University of Georgia.

Last year the city logged 377 bedbug violations, up from just 2 in 2002 and 16 in 2003. Since July, there have been 449. "It's definitely a fast-emerging problem," said Carol Abrams, spokeswoman for the city housing agency.

Like many "bedbug victims," as some call themselves, Josie Torielli has become consumed with the biology of bedbugs since she found them in her home last year. She blamed mosquitoes for the blotches on her body until she turned on the lights one night and found a few of the fiends crawling across her sheets.

She thought she had them conquered, but last week, after nine months of peace, Ms. Torielli discovered the telltale red spots on her sheets, the result of blood-engorged bugs crushed during the night.

"I've become obsessed," said Ms. Torielli, 33, a student who lives in Hell's Kitchen, in Manhattan. "I switched to white sheets so I can see them better, and I've set up a bedbug jail in a Tupperware container that I put on the windowsill to torture them with daylight. It's all-out war."