Scoop up some dirt, and you’ll probably wind up with some slime mold. Many species go by the common name of slime mold, but the ones scientists know best belong to the genus Dictyostelium. They are amoebae, and for the most part they live the life of a rugged individualist. Each slime mold prowls through the soil, searching for bacteria which it engulfs and digests. After gorging itself sufficiently, it divides in two, and the new pair go their separate, bacteria-devouring ways. But if the Dictyostelium in a stamp-size plot of soil should eat their surroundings clean, they send each other alarm signals. They then use the signals to steer toward their neighbors, and as many as a million amoebae