Raleigh, N.C. — "Sleep tight. Don't let the bed bugs bite."

That old bedtime saying has become harder to follow as the number of bed-bug infestations in North Carolina has increased.

Researchers at North Carolina State University study bed bugs, ways to eliminate them and infestations across the state.

"We've seen pretty much a rise in the problem, particularly in this area of the state," entomologist Dr. Mike Wladvogel said.

In the Triangle, complaints about bed bugs rose 50 percent in 2009. Inspectors at Triangle Pest Control said that while two years ago they received one or two calls about bed bugs each month, that rate has gone up to 20 or 30 calls a month.

"Bed bugs are very good hitchhikers," explained Donnie Shelton, owner of Triangle Pest Control. "There's been an explosion in New York, major metropolitan areas. So people, they go out and travel. They pick it up in their luggage. They pick it up in their clothing."

Wladvogel urged that people with bed-bug infestations turn to professionals to get rid of the pests. Bed bugs are resistant to certain pesticides, a problem that N.C. State is researching, he said.

"Bed bug control is not do-it-yourself," Wladvogel said.

Getting rid of an infestation doesn't come cheap. Most companies charge from $300 to $1,000 to treat the area.

The first step is checking for the bugs. Flashlights in hand, inspectors look in every nook and cranny of a building.

"I'm looking for signs of either the live bugs themselves or signs of fecal matter," said Mike Dinatale, lead inspector for Triangle Pest Control. "It should be very hard to find them during the day."

Inspectors showed one extreme case: an apartment loaded with bed bugs, where the infestation had gone untreated. The bugs formed black streaks on the walls.

Cases like that are apparently becoming more common, inspectors said.

"It's all over the place, and it's really only a matter of time before everybody deals with it or knows somebody that does or (has) had to deal with it," Dinatale said.