Nearly eradicated in the United States 50 years ago, resistant strains of "super" bedbugs are infesting mattresses at an alarming rate. In what's being touted as the biggest mystery in entomology, all 50 states are reporting outbreaks of the blood-sucking nocturnal critters. Pest control companies nationwide reported a 71 percent increase in bedbug calls between 2000 and 2005. Left alone, a few bedbugs can create a colony of thousands within weeks. "We never treated bedbugs until 2002. Now we have a dedicated bedbug crew working on this every day," said Luis Agurto, president of Pestec in San Francisco. Bedbugs have been found in moving vans, public transit seat cushions, airplanes, college dorms and even a Bay Area meditation retreat. They spread by hitching a ride on your clothes or in your luggage and crawling off to infest your home or apartment building. Nearly 300 bedbug infestations were reported to San Francisco health officials in 2006, more than double the number in 2004. Most of the cases involved travelers discovering bedbugs in upscale hotels.