 The scene depicting the two pests interacting is symbolic of:
In repose, Taphetta the Ribboneer resembled a fancy giant bow on a package. "There are at least a hundred kinds of humans, each supposedly originating in strict seclusion on as many widely scattered planets. Obviously there was no contact throughout the ages before space travel— and yet each planetary race can interbreed with a minimum of ten others ! "Outside of your own world, there's nothing like your species, except superficially, and that's true of all other creatures, intelligent or not, with the sole exception of mankind. Actually, the four of us here, though it's accidental, very nearly represent the biological spectrum of human development. It's reasonable to assume that, if men were set down on a hundred such worlds, they'd seem to fit in with native life-forms on a few of them. That's what happened on Earth; when Man arrived, there was actually a manlike creature there. "But there are other worlds in which humans who were there before the Stone Age aren't related to anything else there. "Something had to distribute one species so widely and it's not the result of parallel evolution—not when a hundred human races are involved, and only the human race." The theory is that humans who can mate with each other were once physically close. If planetary race F can mate with race E back to A and forward to M, and race G is fertile only back to B, but forward to O, then we assume that whatever their positions are now, at once time G was actually adjacent to F, but was a little further along. When we project back into time those star systems on which humans existed prior to space travel, we get a certain pattern. This is one arm of it as it is today and here are the human systems." And while stars in a given region tend to remain together, there's also a random motion. They were spaced at fairly equal intervals along a regular curve, a horseshoe loop that didn't close, though if the ends were extended, the lines would have crossed. "And whereas there are humans who are relatively near and not fertile, they can always mate with those they were adjacent to two hundred thousand years ago !" "The adjacency mating principle. And, of course, if it were a fast-moving star, it might be completely out of the field of our exploration. We have men who could do the job in a makeshift fashion, but the region we're heading for, while mapped, is largely unknown.
 The lengths all species will go to in order to surpass one another or protect their own status
 The potential danger that could result if intermixing becomes prevalent and social stratification becomes impossible  The reality that 'playing dead' is the best strategy for managing other threatening species who use more overt power to retain superiority  The lengths all species will go to in order to surpass one another or protect their own status  Taphetta's actualized fear that humans will use germ plasm to become biologically superior to his race