Slaughterhouse World, by Ardath Mayhar (epub/Kindle)
The Knackers look like a cross between a spider and a crab, except bigger—much bigger. And meaner—much, much meaner. And they never stop coming.
Joel Karsh is just a grunt slugging it out on Planet 3G 789, a bug factory world, where fresh protein (i.e., human flesh) is being processed for reshipment to enemy depots throughout the cluster. All he wants to do is make it back to the SpaceForce pick-up point. But as his buddies are killed, one by one, and the Knackers swarm ever closer, he's beginning to wonder if he'll even live through the next day.
A rousing SF military adventure by a master storyteller.