In 1979, the police in Schenectady, N.Y., responded to a complaint about a barking dog. When they arrived, however, they found cockroaches streaming from the windows of a two-family home, raining down from trees and darting into the street. Inside, roaches had plastered every wall like stucco and had left bites all over a 64-year-old woman and her 24 dogs, which, it turned out, had been barking for good reason. The swarm comprised approximately one million German cockroaches, perhaps the largest household infestation ever recorded.

In those days, the war on roaches seemed hopeless. The insects were a ubiquitous fixture of kitchens and bathrooms, basements and streets; in 1985, The Washington Post reported that they had infiltrated the Pentagon. Roaches were linked to the spread of infectious diseases like salmonella poisoning and were at least partly responsible for the rising asthma epidemic in inner cities. It was frequently predicted, uncomfortably, that an army of roaches would survive even a nuclear holocaust.

But in the 70's and 80's, scientists were already honing a weapon -- new bait eventually sold as Combat and other products -- that would change the course of the war. Because of it, populations of German cockroaches, by far the most common household variety, have fallen precipitously in many urban areas. ''They were decimated,'' says Phil Koehler of the University of Florida. But could roaches go away for good? And would it really be good riddance if they did?

Of the more than 3,500 species within the insect order Blattaria, only a small fraction cross paths with humans enough to be considered pests. Some, like the enormous American cockroach, or palmetto bug, live mostly in sewers or dark, dank basements. But Blattella germanica, otherwise known as the German cockroach, actually lives with us in our own homes. ''They are an artifact of human existence,'' says Dini Miller, an entomologist at Virginia Tech. In all likelihood, they moved in with humans in Africa, when we first started storing our food and living indoors. ''Since then, they have evolved with us,'' she said.