Are cockroaches helpful

http://www.sciencedaily.com/releases/2008/01/080106132313.htm "For several years, ARS entomologist Bob Pfannenstiel has been studying predators that feed on the eggs of lepidopteran pests of annual crops. Pfannenstiel, who is in the Beneficial Insects Research Unit at Weslaco, Texas, does most of his work on cotton and the pests that plague it, such as bollworm and beet armyworm. In the summer of 2006, he discovered a new predator that feeds on lepidopteran eggs-the Asian cockroach, Blattella asahinai. This roach was observed in large numbers-up to 100 or more per square meter-in soybean fields at Weslaco, yet it causes no damage to the soybeans."