The Jorgall are one of the many minor xenos species that populate the galaxy of Warhammer 40,000. They were found in the Tasak Beta and Fallon systems, though it's suspected they are pretty much nomads, living in their massive cylindrical spaceships.
Biology and Behaviour
The Jorgall were an insectoid species that lived hive like societies, with all different members showing different anatomy depending on their role in the colony. Usually the adults could reach a height around 4.5m tall, though that varied. They were born with three arms and three legs, scaly skin and with brains inside their torsos and not their heads. The atmosphere of their ships was composed primarily by chlorinated compounds, which suggested they breathed chlorine instead of oxygen. They frequently showed different augmetics, once again, designed to fulfill a particular role within the colony. Some of them could even develop psychic abilities, though whether their hive behaviour was psychic-based or pheromone-based is up to speculation. Their reproduction was similar to that of ants or termites, with a Jorgall queen dedicated to egg production.
History with the Imperium
Like pretty much all other xenos, the Jorgall's relation with Humanity and the Imperium was of war. Apparently the Jorgall were raiding and attacking nearby human systems at the time of the Great Crusade. And, like many other xenos at the time, were practically exterminated and wiped out of the galaxy. In particular, the Death Guard was sent to deal with them, with one particular episode of their clash being very noteworthy: the fight between Nathaniel Garro and a squad of Sisters of Silence against a mutated Jorgall psyker, which would affect Garro's perception of the great scheme of things during the immediate moments before the Horus Heresy. Afterwards, the Jorgall ship was hurdled into a nearby star, just in case some of the bugs had survived the cleanup. However, once the Heresy ended, the Jorgall were one of the xenos species imprudent enough to try and recover the lost space against the Imperium, something really unwise considering the amount of RAGE the Imperial forces had right after the entombment of the Emperor in the Golden Throne. Afterwards there is pretty much no mention of them, so they may have finally been wiped out during the crossfire between the Imperium and the scattered traitor forces during the Great Scouring, though being nomadic, nobody can say with certainty that they are truly gone.