The Warrior and the Biologist — Susan Kelley

An alien invasion pushes mankind to the point of extinction. The raynids prey on humans as a food source, swarming through the universe like locusts from a nightmare. A small band of survivors of the distant planet of Gaviron hunt the monsters but they're slowly losing the war. Biron, highly-trained and gifted warrior of Gaviron, reluctantly agrees to a last desperate strategy. The goal isn't to defeat the raynids but to make sure a few small pockets of humanity survive. To do his part, Biron takes on the role of protector on the small Earthling colony of Blithe. In exchange, the people of Blithe must offer up one of their women as Biron's bride so that a small piece of Gaviron will live on. Heartbroken by the years of fighting the raynids and losing everyone he's loved, Biron doesn't care who he marries. Esta Brunner, intelligent, brave and attractive, makes as good a choice as anyone.