Class: Non-humanoid race  Size: Approx. 2.75m  Origin: Fluidic Space

 In their search for further species worthy of assimilation, the Borg first encountered Species 8472 after they found a way to enter fluidic space sometimes in 2373. They believe this realm to be ripe for the taking.  The Borg is are impressed by species 8472 spaceflight  and computer technologies, which are entirely biological in nature.  Perceiving Species 8472 as the pinnacle of organic evolution, the Borg collective decides to add this race's distinctiveness to its own.   However, Species 8472 turned out to be immune to the Borg's assimilation attempts and the invasion of their realm provoked

a war, which quickly evolved into the first real threat the Borg had faced in thousands of years. nearly twice a human's size, the tripodal, insectoid species 8472 are among the most dangerous creatures ever encountered by the crew of the federation starship u.s.s. voyager.  species 8472 uses ships made of the same organic materials found in their bodies, and their vessels secrete corrosive substances capable of quickly penetrating virtually any other ship's hull.  able to thwart deflector shields and scanners, this race can attack with impunity.  during its first five months fighting the Borg, species 4 engages the Borg on at least twelve occasions, handily defeating them each time and driving the borg out of a vast swath of their own delta quadrant territory. 

With their superior technology, Species 8472 was able to annihilate large amounts of Borg and their ships and even planets.  Species 8472 was forced to retreat when the crew of the USS Voyager armed warheads with modified nanoprobes capable of destroying their bio-ships.

Concerned about the threat posed by Humanity with its modified nanoprobes-warheads, Species 8472 created a simulation of Starfleet Academy on Earth inside a Species 8472 bio-sphere in the Delta Quadrant as a training ground for a potential infiltration of the Federation. However, the plan was uncovered and eventually stopped by the crew of the USS Voyager, who convinced Species 8472 that the Federation had no hostile intention toward them by giving them their modified nanoprobes warheads in hope that Species 8472 could adapt their vessels.

Species 8472 attacks with their claws whenever they can. This will transfer their cells to the victim. These cells, once in the victim's blood, will begin to consume the body from the inside out, essentially eating the victim alive. The victim will be conscious during this process because all sedatives and other treatments to the infection are neutralized immediately.

While the fire power of one ship is extraordinary,

they can combine their fire power by forming a circle with a number of other ships, with one ship in the center of the circle. All the ships fire at the main center ship, which collects the fire power and amplifies it out, causing enough fire power to destroy a planet. Species 8472 are highly intelligent and devious. When they enter the enemy's ship, it will do whatever is the most efficient way to destroy the ship.

species 's bio-ships generate energy using organic conduits which carry electrodynamics fluids: the bio-ships also carry organic binary matrices laced with neural peptides, devices which apppear to be analogous to the computer systems used on federation vessels.  in addition, the bio-ships are resistant to federation transporters and tractor beams.

the bio-ships of species 8472 enter and exit fluidic space by means of artificially generated singularities.