Add another entry to the list of pests that terrorize New Yorkers. Bedbugs, the subject of so many parents’ bedtime warnings, are making a comeback.

“We first noticed some bedbug activity around four to five years ago, which caught me off guard, because we’ve never dealt with this thing before,” the president of Bug Off Pest Control, Andy Linares, said. “Since that time,” he said, “it’s been growing exponentially.” In addition to providing pest-control services, his company trains exterminators in fighting bedbugs and has scheduled a March 30 seminar on the subject.

Bedbugs are small, wingless, flat bugs, similar in size to an apple seed. They create homes in any cracks, crevices, bedding material, and other hideaways around sleeping areas of warm-blooded creatures. They are known to feed on cats and dogs as well as humans.

Like vampires, the insects emerge at night to feed on human blood, only to scamper away and hide before daybreak. Bedbug saliva carries an anesthetic agent, which makes the 10-minute feeding process pain-free. Come morning, however, a bedbug infestation means irritating bites that leave itchy, bloody welts on the host’s skin, comparable to hives.

“They bite me everywhere, absolutely everywhere, anywhere exposed,” one victim, Monika Krejcirova, said.

She noticed a bedbug the first night she moved into her Hell’s Kitchen apartment after emigrating recently from the Czech Republic. “I picked it up from the bedsheet and it just popped,” she said. “I didn’t think anything of it. After several weeks, I started getting bites every night. Aside from the irritation, the mental feeling is also really disgusting – the thought of things crawling over me every night is very bothering.”

Ms. Krejcirova added: “It makes us very paranoid. Every little tickle I’m searching myself. It’s also very embarrassing when people see the red spots all over you. My family is supposed to visit in the fall. I’m still hoping they’ll be able to.”

Untreated infestations can quickly grow out of control. Bedbugs reproduce rapidly and do not easily die: They can withstand a year or more without feeding, in climates of near freezing to 113 degrees.

According to Orkin, a pest control company, females lay 10 to 50 eggs every 3 to 15 days, producing more than 500 in a lifetime. Eggs, too, can lie dormant for more than a year without food or attention.

“We have seen an increase in complaints, over the past six or eight months in particular,” a spokesman for the New York City Housing Authority, Howard Marder, said. “We’re coordinating our efforts with the health department on this, but we think it’s containable.”

According to a clinical associate professor of medicine at the NYU School of Medicine, Marc Siegal, hospitals have seen an increase in patients coming in to inquire about bedbug bites in the past couple of years, but Dr. Siegal said: “While bedbugs are a great annoyance, they do not transmit disease – there’s no health scare involved.”

As bedbugs were essentially extinct after the introduction of DDT in America during World War II, their re-emergence came as a surprise, exterminators said. Mr. Linares attributes the pests’ resurgence to evolving cultural habits. Foremost is the increase in international travel to tropical areas, which has been facilitated by cheaper fares. “Hitchhiking” bedbugs catch a ride back to America from Third World countries, where they join their host in hotels or hostels.

Also to blame is the propensity of some New Yorkers to recycle mattresses, Mr. Linares said. “People take old mattresses, fix them up, and sell them as new,” he said. “Factories in Bronx do this – it’s seemingly a big industry.” He added, “People also see headboards, mattresses, or other bedding materials on the street and have a tendency to bring them into their homes.”

To exterminators, a primary factor is their dwindling arsenal of anti-pest tools. DDT was banned in this country in 1972, and Mr. Linares said two whole classes of insecticides – organophosphates and carbamates – were recently pulled from the market.

“Pyrethroides are all we have now to work with,” he said. “And as they can develop a resistance to this, we’re going to be hitting a brick wall real soon as they develop a stronger immunity.”

An entomologist who has written about bedbugs, Mike Potter, said: “I refer to this as the perfect storm of pest control. We have these cryptic bugs that attack you during the night; we’ve been told not to spray in people’s beds and bedrooms, and we’ve lost most of the formerly effective products we had.”

“In New York, bedbugs are going absolutely bonkers, and the problem is getting worse and worse,” Mr. Potter, professor of urban entomology at the University of Kentucky, said.

The president of Metro Pest Control, Ben Weisel, described the effects of an untreated infestation.

“There was an elderly fellow who lived alone,” Mr. Weisel said. “He wasn’t able to take care of himself. The property owner had called to get the treatment. He had a beard like ZZ Top, and when we got there, his beard was actually moving – it was totally infested. They had to shave his beard and totally fumigate the apartment. Bedbugs had infested at least 20% of the building.”

When repeated treatments prove ineffective, some bedbug victims have grown so frustrated they pick up and move – leaving their furniture behind. When an entire building gets hit, landlords report having spent tens of thousands of dollars combating the critters.

An infestation is not infrequently a product of bad luck, but there are precautionary measures available. It’s advisable to seal all crevices surrounding sleeping areas with a silicone sealant. Clutter should be avoided.

Signs of bedbugs include brown or red spots on sheets and around bedding material. In severe infestations, there’s a musty, sweet odor. Bedbugs are rarely ever seen.

Education, pest-control experts said, is the key to containing bedbugs. Most important, travelers need to be wary of unclean hotels in tropical locations.

“Bedbugs are like a nursery rhyme. Many people don’t even think they’re real,” Mr. Potter said. “Well, as people continue to travel, they’re going to be reacquainted.”

BEDBUGS (Cimex Lectularius)

APPEARANCE

Flat, oval-shaped, three-sixteenths of an inch long. They are brown, but turn reddish after engorging on blood.

REPRODUCTION

Females lay 10 to 50 eggs every three to 15 days – 70 degrees is the preferred temperature for laying eggs. Three or more generations can be produced per year. Females can lay 500 eggs in a lifetime. Eggs hatch in six to 17 days, although it takes longer in colder temperatures.

RESIDENCE

Bedbugs live near their food, sleeping humans. They create homes in mattresses, furniture, pictures, speakers, wall outlets, torn wallpaper, window frames, headboard, electronic equipment, ceiling fans, air conditioners, etc. They are attracted to breath (carbon dioxide specifically) and body heat.

HISTORY

Bedbugs are a resilient species, referenced in Greek literature as far back as the time of Aristotle.

GROWTH

Newly hatched nymphs shed their skin (“molt”) five times before full development. A blood meal is required between each molting. The process takes around a month.

RANDOM

Bedbugs cannot fly, but can scamper quickly. They are nocturnal. Bedbugs die at 110 degrees – so steam-cleaning can help eradicate an infestation. The National Pest Management Association reports a 500% increase in infestations in the past four years.

DETECTION

Look for reddish spots (blood) on sheets and mattresses. Try to detect a musty, sweet odor (like soda syrup).