For thousands of years the Borg spread throughout the galaxy, conquering, assimilating, and thus destroying countless civilizations. Following every encounter, the Borg catalog each new species with a numerical designation, rather than a proper name. Often the original species name is lost, forgotten or deleted as irrelevant. Conversely, the species designations gave a sense of the long and terrible history of the Borg and the thousands of species they encountered and absorbed.
The whole race, except for 10,000-20,000, has been assimilated.
Borg Queen’s species
The Borg Queen mentions to Seven that she came from Species 125.
This species originally devised the procedure that led to Seven’s method to save Neelix with nanoprobes.
We don’t know why Ferengi are categorized so early in Borg history. Maybe some of them ended up in a wormhole long ago, or Seven was simply confused and meant to say “Species 5180”.
Seven: “A small freighter, containing a crew of 39 taken in the Dalmine sector. They were easily assimilated. Their dense musculature made them excellent drones.”
From Galactic Cluster 3
Their technology of autonomous regeneration sequencers was assimilated by the Borg.
Assimilated 229 years ago. According to Seven, Species 262 was “primitive, but their oral history referred to a powerful substance which could burn the sky [the Omega Molecule].”
They used a similar technology to the energy barrier encountered by Seven and Chakotay.
According to Seven of Nine, “they were unworthy of assimilation.”
Seven and Naomi see a Shivolian in the mess hall, while Voyager is docked at the Markonian outpost.
species of Four of Nine
Four of Nine is against disassembling a dead drone, because this would be against the will of Brothara, a supernatural deity worshipped by Species 571.
Mezoti identifies herself as being of that species number. We should trust her.
Icheb belongs to this species. The number has not been ultimately confirmed, the information may come from the script.
Seven: “Vulcan. Species 3259. Your enlarged neocortex produces superior analytical abilities.”
Seven: “Technologically advanced, extremely violent. They make excellent tactical drones.”
Seven mentions that a small ship of that species was found, the passengers killed (probably by the Hirogen).
Borg Queen: “Species 5618, human. Warp-capable, origin grid 325, physiology inefficient, below average cranium capacity, minimum redundant systems, limited regenerative abilities.”
When Neelix tells of an entity of possibly non-corporeal nature, Rebi suggests that it could have been Species 5973.
Both the Borg and the Federation believed that the species was extinct.
Seven: “Species 6339, Humanoid. Warp-capable. Origin: Grid 124, Octant 22 Theta. They first encountered the Borg approximately four years ago. Since that time, 11 billion individuals have been assimilated. Three days ago, the Collective detected one of their last surviving shuttlecraft. A cube was sent to intercept it.”
Erin and Magnus Hansen examine a drone on the Raven. “Species 6961…Ktarian…Tritanium infrastructure. He’s a tactical drone.”
Species 8472 is a non-humanoid species from a realm called “Fluidic Space”, impervious to assimilation and to Borg weapons.
Seven is supposed to assist in the assimilation of a planet with 329,000 members of this species.