Spore Mines (Boletus minoris), are used by the Tyranids as living, floating mines which explode if any non-Tyranid lifeform gets too close to one. Spore mines are grown and launched by Biovores. They grow deep inside a Biovore's body and are then launched via a powerful muscle spasm through the Biovore's dorsal aperture and hurled across the battlefield.
An internal gas bladder in the spore mines inflates allowing them to drift down towards the ground, where they do not detonate upon impact but when they sense the proximity of a non-Tyranid. They have been known to drift for solar days, weeks or even Terran years until an unwary foe comes too near. Alternatively, spore mines can also be seeded onto worlds from orbit.
Spore mines possess a rudimentary animal intelligence and are full of poisons, toxins, viruses and corrosive chemicals and are covered in sensitive feelers which seek out heat and vibrations. They are also able to sense nearby enemies' weapon fire and will explode in the hope of killing the enemy firing.
All of the spore mines in a cluster are linked, and when one explodes, they all do even if there are no enemies nearby. If a mine is slain it will also explode.
Spore mines come in one of three forms most often:
- Poison Spore Mines - Full of poisons and toxins, the mine can overcome any physiology. The poisons include highly reactive inorganic poisons, hemo-toxin, afla-toxin, neuro-toxin and phage cells.
- Frag Spore Mines - It has an iron hard shell which shatters when the mine explodes and sends shards of the shell in all directions, which can scythe down light infantry but can also cause lethal infections and sepsis.
- Bio-Acid Spore Mines - The acids are thick and viscous, allowing them to cling to their victim to maximize the effectiveness. They have been known to dissolve everything up to, and including, ceramite plate.
- Codex: Tyranids (5th Edition), pg. 48