Nicknamed "the Eight Plague" by their Dominion enemies, the arbeh (Communitas locusta xenos) are an alien species operating with a pseudo-hive consciousness and are a thorn in the side of minor human and xeno settlements living near the galactic core. The arbeh are small, centipede-like aliens with a thick coat of fur, a head and a long prehensile tail. Living on a dimly-lit world, all arbeh have massive eye clusters situated on their "head" and their fur is colored in very bright colors (that humans cannot perceive, as they are sensitive to light in the ultraviolet range). The arbeh sense of smell is also well-developed, especially when it comes to pheromones. Each arbeh has two large sails on its back, which can be retracted or spread out as a form of communication. Arbeh tails are very sensitive and can be used as antenna or another way to communicate. While their tails are prehensile, the arbeh use their mandibles to manipulate tools, a limitation which has severely retarded their technological progress. 

The arbeh have three castes: royalty, conductors and workers. The royal caste is composed of fertile queens-to-be and infertile "sovereigns." The conductors, chosen shortly after birth, are injected with a special chemical that enhances the growth of their pheromone glands and, as their name suggests, allows them to manage the workers with little resistance. Workers make up the bulk of the arbeh species and are damned to work their assigned jobs for the rest of their short lives. Contrary to popular belief, workers are not born to be soldiers, farmers or to specially perform any other task. These jobs are assigned later by arbeh society.

Arbeh society is organized by "nests;" contrary to popular belief, these nests are not "controlled" by their queens, thanks to their strange and brutal reproductive cycle. Arbeh queens are fertile females that have the (mis)fortune of having many of the tiny, parasitic arbeh males attach themselves to her. After receiving the sperm from the males, the eggs in the queen's womb are fertilized and eventually hatch, the young burrowing their way out of her body and consuming it for their first meal. The young are rounded up by sovereigns, the queen's infertile sisters. Using their pheromones (or pheromones stolen from another "royal family") they are able to take control of the larval arbeh without resistance. The males are quickly segregated and bred separately, to be used during breeding season and conductors are chosen among the larvae. Eventually, the ruling sovereign will pick one of the conductors and raise them as a successor, educating them in politics and feeding them various hormones to transform their bodies into that of a true sovereign. When breeding season arrives, a single conductor is given a different set of hormones and thrown into a pit of arbeh males. 

Conductors are educated separately from workers, taught to love the workers but at the same time never forget that they are superior to them. Eventually, all managers and workers will be assigned a specific task which they will perform for the rest of their lives, as decided by the leadership. This is viewed as the highest honor and those who do not have assigned tasks in the nest are ostracized; those who reject their calling are killed. Arbeh psychology is heavily communal, believing that the interests of the individual are subordinate to the greater good of the nest. This reverence for community has evolved to have religious overtones and all arbeh societies believe in the binding force of collectivism. Of course, this has also extended to reverence for the royal leadership, who are revered as gods. The pheromone secretions of an arbeh sovereign are regarded as sacred and, should a sovereign fall in battle, it is the duty of the surviving soldiers to prevent the corpse of a sovereign from falling into enemy hands. 

The arbeh are not united as a species, with hundreds of thousands of different nests living on the arbeh worlds. Wars can spark over petty political issues, just as they do among humans, but other times wars are fought over pheromones. If a sovereign can take control of another family's pheromones, they could absorb that family into theirs and their power in the great game of politics is increased. Their belligerent nature has led them to conflict with the humans, whom they believed they could absorb in a similar manner. When humans saw the arbeh digging through the corpses of captured prisoners in an attempt to find their pheromone glands, the humans were not pleased. This, and many arbeh nests assaulting human worlds in rapid succession, gave rise to the myth that they are a horde of locusts that wish to consume mankind. 

Arbeh technology is laughably primitive, comparable to Earth in the late 21st century. Faster-than-light travel is a recent invention for the arbeh, having been invented in the last century. Being extremely fractured, there are no arbeh city-states to fully invest in large projects; space travel is only possible when several arbeh nests work together. This has squashed any possibility for large military-industrial complexes, as no arbeh nest wants to give its opponents an edge. This has led to warfare staying at a medieval level, if only with superior materials science. However, the arbeh excel in terraforming technology, which has allowed them to colonize many worlds in a very short period of time. 

Although many small communities near the core would disagree, the arbeh are not impressive on the battlefield. They lack any sort of projectile weaponry or heavy weapons platforms, forced instead to swarm the enemy and assault them with various weapons attached to their legs and heads. This has led to the arbeh suffering immense casualties even in victory. However, numbers could make all the difference when assaulting small communities which cannot sustain the casualties inflicted upon them by the xeno menace. This has led to calls for attacks against the arbeh by the larger human powers to fall on deaf ears, as they could not be bothered with exterminating a minor nuisance when more pressing issues are at hand.

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