"Harvesters are a ubiquitous threat in the galaxy having spread easily as stowaways in the darkest depths of starships. Though they lack any true intelligence, they more than make up for it in pure ferocity. They gained their name from the shape of their wickedly sharp forelimbs and their tendency to collect their victims' corpses and drag them back to their colonies. When prey is scarce they enter hibernation, sometimes for years at a time. Once awoken the only thought on a Harvester's mind is the need to feed and nothing short of being put down for good will stop them from doing so. In the circuit they've proven to be excellent arena hazards. Nothing livens up a match quite like a pack of hungry Harvesters. Able to adapt quickly to any environment they instinctively hunt all other predators, consuming them and taking their place in the food chain. Unfortunately for most settled worlds that spot is usually occupied by a sentient species."
Though the basic shape of a harvester remains the same wherever you encounter them, they often have subtle differences based on the environments they call home. Those found in areas of high volcanic activity tend to have bulkier claws for digging through the much tougher mineral composition of the surrounding dirt. Others have adapted acid spraying tubes in their claws perfect for weakening the hulls of starships. Harvesters who have adapted to mountainous or forested environments often sprout additional barbs on their claws that are as suited for climbing as they are for combat.
Although arthropodal in nature they share more in common with Earth's crabs than with it's insects. All Harvesters are capable of reproduction being sexually neutral, they can mate with any other member of their species. Once mated both members gestate clutches of eggs. This makes destroying a colony for good nearly impossible unless every single member is destroyed.
The basic life cycle of a Harvester starts with a hard shelled egg laid by it's parent. They hatch from these eggs after 14 - 17 days as soft carapace nymphs. Their bodies harden with another 5 -7 days as they continue to live inside the colony feeding on the kills of their brood mates. Once their bodies are fully formed they are spurred by their instinctual drive to hunt and leave the colony until their first kill. They then return, taking on whatever role the colony is most in need of.
Though not particularly intelligent numerous tests have ruled out any kind of pheromonal, visual, or verbal communication between members of a given colony. They are also unable to communicate with any members of another colony. Though nothing is concrete current working theories are that they share some kind of low level psychic link. This theory also serves to explain their ability to "know" where threats are even when miles away from the initial colony member that detected them.
Members of different colonies do not tolerate each other. On the rare occasion that two colonies meet they immediately attempt to wipe each other out. All colony efforts divert to destroying the new found threat and nothing short of one side's extermination will change that. Many xenobiologists believe this disunity among colonies to be the main reason they haven't taken over the galaxy.
When food becomes scarce most of a colony will begin to hibernate. A few select Harvesters will continue to operate the colony until a new food source has been identified. This incidentally is also how they end up spreading, as the new food source is often an expedition force or a colonization effort. The active members of the Harvester hive will either incidentally find themselves in the hold of a starship bound for a new world or they will end up becoming a boogeyman for the new settlers, hunting them down one by one as the new glut of food wakes up more of the hibernating colony. By the time the settlers know what is going on it is generally too late.
The Harvester's have found a niche infamy within tournament circuits. Used as arena hazards and main events Harvesters have become a highlight for many fans. The desperate struggle between man and beast being a strong draw especially for teams struggling to stay relevant. They are also extremely useful for livening up a match that begins to stall. After all Harvester's pay little attention to cover tactics or intimidation and are great for flushing out combatants that are dug in too deep.
Most people living out in the wider galaxy will never know harvesters for anything outside of their circuit appearances and as such see them only as yet another terrifying beast that lives out in the void between worlds that they'll never have to deal with. All the more ironic when containment procedures are not followed closely and a few Harvesters escape from the battle arena into a vast ecumenopolis. Then again, by the time anyone realizes that there is a problem, it'll be too late to do anything about it.